Comparative Efficacies Of Current Second And Third Generation Fluoroquinolone Antibiotics On Systemic Escherichia Coli In Broiler Chickens In Qalyubia Farms

Comparative Efficacies Of Current Second And Third Generation Fluoroquinolone Antibiotics On Systemic Escherichia Coli In Broiler Chickens In Qalyubia Farms | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Comparative Efficacies Of Current Second And Third Generation Fluoroquinolone Antibiotics On Systemic Escherichia Coli In Broiler Chickens In Qalyubia Farms Ali M. Asy, Amany O. Selim, Dalia M. Azab, Eman A. Abozeid, Mona A. Elkholy, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8790151/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 12 You are reading this latest preprint version Abstract Avian pathogenic Escherichia coli (APEC) causes severe colibacillosis in poultry. This study compared the efficacy of the third-generation fluoroquinolone levofloxacin and the second generation enrofloxacin against APEC. In vitro, 155 samples from broiler farms in Qalyubia, Egypt, yielded 43 E. coli isolates, with 16 forming strong biofilms. Antibacterial sensitivity testing revealed levofloxacin had a higher susceptibility rate (43.75%) and larger inhibition zones (26 mm) compared to enrofloxacin (18.75%, 13 mm). Levofloxacin demonstrated superior antibacterial activity compared to enrofloxacin (13 mm). In vivo, 150 broiler chicks were experimentally infected with a common APEC O2 strain and divided into negative control, positive control, levofloxacin-treated, enrofloxacin-treated, and enrofloxacin and colistin combination groups. Levofloxacin treatment resulted in significantly higher body weight gain, lower mortality (3.33% vs. 6.67%), and improved feed conversion ratio compared to enrofloxacin. It also produced better hematological and biochemical profiles, reduced oxidative stress markers (MDA, SOD, GSH), and achieved lower bacterial counts in organs posttreatment. The results conclusively demonstrate that levofloxacin is more effective than enrofloxacin in treating colibacillosis, offering enhanced performance, health outcomes, and microbiological clearance in broiler chickens. Health sciences/Diseases Biological sciences/Microbiology Levofloxacin Enrofloxacin Escherichia coli Antioxidant enzymes Broilers Introduction Colibacillosis, primarily caused by avian pathogenic Escherichia coli (APEC), is a significant bacterial infection affecting broiler chickens, leading to high mortality rates and substantial economic losses in the Middle East and the global poultry industry. The infection can disseminate to internal organs, leading to conditions such as septicemia, peritonitis, and air sacculitis [ 1 , 2 ]. Beyond its impact on animal health, APEC, a member of the Enterobacteriaceae family, poses a potential zoonotic risk. Although considered a commensal organism in humans and animals, it is frequently used as an indicator of enteric pathogen presence [ 3 ]. Some strains of avian pathogenic Escherichia coli exhibit genetic similarities to human extraintestinal pathogenic E. coli, including uropathogenic E. coli and neonatal meningitis E. coli. This genetic resemblance suggests that APEC may have the potential to cause infections in humans, such as urinary tract infections and meningitis [ 4 ]. APEC's capacity to spread antimicrobial resistance genes through horizontal gene transfer poses a serious threat to both animal and human health. Effective control requires improved biosecurity measures in poultry farming, prudent use of antibiotics, and continuous monitoring of resistant strains [ 5 ]. Fluoroquinolones (FQ) are synthetic bactericidal agents having a bicyclic core structure related to 4-quinolone, widely used in both human and veterinary medicine to treat a variety of serious bacterial infections. They are particularly effective against Escherichia coli and other Gram-negative bacteria [ 6 ]. In poultry, FQ have been widely employed to manage avian colibacillosis [ 7 ]. FQ exert their antibacterial effects by disrupting bacterial DNA synthesis, leading to cell death by inhibiting topoisomerase enzymes—specifically DNA gyrase (topoisomerase II) in Gram-negative bacteria and topoisomerase IV in Gram-positive microorganisms. These enzymes play critical roles in DNA replication and transcription [ 8 ]. Enrofloxacin, a second-generation fluoroquinolone, has been extensively utilized in veterinary medicine for the treatment of colibacillosis; however, its use has come under scrutiny due to rising concerns regarding antimicrobial resistance (AMR) and regulatory restrictions imposed by health authorities like the European Medicines Agency (EMA) [ 9 ]. Consequently, there is an urgent need to explore alternative therapeutic agents that can effectively manage colibacillosis while minimizing the risk of resistance development. Levofloxacin, the L-enantiomer of ofloxacin, is a third-generation fluoroquinolone that exhibits a broader spectrum of activity and an improved pharmacokinetic profile, including near-total oral bioavailability [ 10 ]. Consequently, it emerges as a promising candidate for treating infections caused by APEC. This study aims to evaluate the susceptibility of Escherichia coli strains, isolated from broiler chickens’ farms in Qalyubia, Egypt, to clinically relevant fluoroquinolones, enrofloxacin (second generation) and levofloxacin (third generation), to determine the prevalence of fluoroquinolone-resistant E.coli. Additionally, it aims to conduct a comparative study of the clinical effects of Levofloxacin and Enrofloxacin in broiler chickens experimentally infected with APEC. By evaluating treatment outcomes, this study seeks to provide valuable insights into optimizing therapeutic protocols for managing colibacillosis in poultry. Furthermore, understanding the differential impacts of these two fluoroquinolones may contribute to better stewardship practices in veterinary medicine and help mitigate the challenges posed by antimicrobial resistance. MATERIAL AND METHODS 1. In-Vitro Study: 1.1. Collection of samples A total of 155 samples (liver, heart, and lungs) were collected from freshly dead and septicemic broiler chickens older than two weeks showing symptoms and postmortem lesions of colibacillosis. The samples were collected from broiler chicken farms located in various areas of Qalyoubia Governorate, Egypt, between 2024 and 2025. Appropriate permission was obtained from the farm owners prior to sample collection and conducting the research. The samples were collected in sterile tubes containing buffered peptone water and then transferred immediately to the laboratories of the Animal Health Research Institute (AHRI) in Benha city. 1.2. Isolation and identification of E. coli The collected samples were initially incubated in nutrient broth at 37°C for 24 h. E. coli isolation was performed using selective media: Eosin Methylene Blue (EMB) agar (OXIOD) incubated at 37°C for 24 h, and Tryptone Bile X-glucuronide (TBX) agar (HIMEDIA) incubated at 44°C for 37 h. Characteristic colonies from these plates (metallic green on EMB and blue-green on TBX) were purified on tryptic soya agar for biochemical testing. The resulting pure colonies were then preserved in brain heart broth with 30% glycerol at -20°C for subsequent analysis (Markey et al.[ 11 ] and ISO 16649-2). 1.3. Serological identification of E. coli The E. coli isolates were serotyped at the Animal Health Research Institute, using "SEIKEN" polyvalent and monovalent O and K antisera (MAST ASSURE™), according to the method of Markey et al. [ 11 ]. Briefly, a loopful of a 24-hour-old colony from nutrient agar was emulsified in physiological saline on a slide, mixed with a drop of antiserum, and observed for one minute. 1.4. Antibacterial sensitivity test The disk diffusion method was applied according to CLSI 2024. The antimicrobial discs of levofloxacin, enrofloxacin, norfloxacin, colistin, and levofloxacin + Nosihertide were used. 1.5. Biofilm Formation The biofilm-forming capacity of the E. coli isolates was assessed using Congo Red Agar (CRA). Isolates that formed black colonies with a dry, crystalline consistency were classified as strong biofilm producers, while those that remained pink were considered weak producers. The assay was performed in triplicate and repeated three times independently. Edwardsiella tarda MW362141 was included as a positive control, following the methodology described by [ 12 ]. E. coli biofilm production was induced on microtiter plates. After 24 hours, antibiotics were applied to the biofilm, and remaining viable cells were quantified by plating on MacConkey agar and measuring colony-forming units (CFUs). The percentage reduction in CFU counts post-treatment indicated the biofilm penetration efficacy for each antibiotic. 2. In-Vivo Study: 2.1. Birds : A total of 150, apparently healthy, one-day-old, unsexed broiler chicks of a commercial breed (Cobb 500) were purchased from El-Watania Poultry company. 2.2. Drugs : Levofloxacin (Lexoflon OR®, NITA-FARM company, Russia. Each 1 ml contains 150 mg Levofloxacin). Enrofloxacin (Enroveto 20®, VMD company, Belgium. Each 1 ml contains 200 mg Enrofloxacin). Enrofloxacin + Colistin (Enronit OR®, NITA-FARM company, Russia. Each 1 ml contains 100 mg of Enrofloxacin + 1000 000 IU Colistin). 2.3. Experimental design : One hundred and fifty chicks were randomly assigned to five groups, with 30 chicks in each. Group 1 served as the control negative group, consisting of non-infected, non-treated chicks. The remaining four groups were orally infected with the APEC O2 serotype strain on day 14. This serotype is one of the most common strains in the Middle East and North Africa region (MENA). The infectious dose was 0.5 ml of APEC O2 suspension per bird, containing 9.0 × 10^8 CFU/ml. Group 2 was the control positive group, infected but untreated. Group 3 was infected and treated with Levofloxacin at 7.5 mg/kg body weight in drinking water for five consecutive days, from day 16 to day 20, which is one day after infection. Group 4 was infected and treated with Enrofloxacin at 10 mg/kg body weight in drinking water for five days from day 16 to day 20, starting one day after infection. Group 5 was infected and received a combination of Enrofloxacin and Colistin at 10 mg/kg and 500,000 IU/kg body weight, respectively, in drinking water for five consecutive days from day 16 to day 20, starting one day after infection. During the entire experiment, the chickens were fed a commercial balanced ration ad libitum and had free access to water. The feed was verified to be free of antimicrobial additives. 2.4. Growth performance parameters : The chicks were individually marked and weighed at one day old, then body weight (BW) was recorded weekly till the end of the experiment (the fifth week). Cumulative feed consumption, cumulative body weight gains (BWG), and feed conversion ratios (FCR) were calculated [ 13 ]. The mortality rate was also recorded and calculated. 2.5. Hematological parameters : The blood samples were obtained from the wing vein of five birds from each group on the 21st, 28th, and 35th days of age. Each sample was divided into two portions. The first portion was collected on tubes containing EDTA and used for the determination of red blood cell (RBC), white blood cell (WBC), hemoglobin (Hb) concentration, and packed cell volume (PCV) [ 14 ]. The second portion was allowed to separate the serum and kept at -20˚C [ 15 ]15to determine biochemical parameters. 2.6. Biochemical parameters : The separated serum samples were used to determine the activity of serum Alanine aminotransferase (ALT), Aspartate aminotransferase (AST) [ 16 ]., serum uric acid [ 17 ]., and creatinine [ 18 ]. 2.7. Oxidative stress parameters : Liver and kidney tissues were obtained from five birds in each group on the 21st, 28th, and 35th days of age. These samples were preserved at -20°C. Subsequently, the tissues were processed into 10% homogenate samples using normal saline to assess oxidative stress parameters, including Malondialdehyde (MDA) [ 19 ], Superoxide Dismutase (SOD) activity [ 20 ], and Reduced Glutathione GSH concentration [ 21 ]. 2.8. Microbiological Efficacy : APEC was isolated from five samples per group, collected from the bone marrow, liver, kidney, spleen, and lungs, at three time points: 13, 15, and 21 days of age) [ 22 ]. The initial isolation on day 13, conducted one day before challenge with the E. coli O2 strain, confirmed the absence of a natural APEC infection in all experimental birds. The subsequent isolation on day 15, one day post-challenge, verified the successful establishment of the infection. The final isolation on day 21, following the conclusion of all treatments, served to determine their microbiological efficacy. 2.9. Statistical analysis The data were analyzed by determining the normality via the Shapiro-Wilk test. The differences between groups were analyzed by One-Way ANOVA followed by Duncan's multiple comparison Post Hoc tests [ 23 ]. The Statistical Package for Social Science (IBM SPSS, version 28.0, (2021); SPSS Inc., Chicago IL, USA) was used. Probability values of less than 5% (P < 0.05) were considered significant [ 24 ]. Data were represented as mean ± standard error of mean (SEM). 2.10. Ethical approval and ARRIVE guidelines All animal experimental procedures were approved and carried out in accordance with the ethical guidelines of the Research Ethics Committee at the Animal Health Research Institute, Agriculture Research Center (ARC), Giza, Egypt. The ethical approval was granted specifically for the animal study component of the research protocol. All methods involving animals are reported in accordance with the ARRIVE guidelines ( https://arriveguidelines.org/ ) to ensure transparent and comprehensive reporting of animal research. Results 1. In-Vitro studies: 1.1. Isolation and identification of E. coli: Among the 155 samples, 43 isolates were identified as E. coli. Specifically, there were 34, 5, and 4 E. coli isolates obtained from the liver, lung, and heart, respectively. 1.2. Serological identification of E. coli: There are 16 strong biofim forming E.coli isolates. They were serotyped as in table (1). Table (1): Isolation and identification of the strong biofilm forming E. coli isolates. E. Coli isolate No. of isolate number Percentage (%) O2:K1 6 37.50 O55:K59 2 12.50 O44:K74 4 25.00 O26:K60 3 18.75 O114:K90 1 06.25 Total 16 100.00 1.3. Antibacterial sensitivity test The in vitro sensitivity testing of 16 strong biofilm forming E. coli isolates revealed superior efficacy of levofloxacin compared to enrofloxacin. As shown in Table (2) levofloxacin exhibited the highest susceptibility rate, with 43.75% (7 out of 16) of isolates classified as sensitive, compared to only 18.75% (3 isolates) for enrofloxacin. The levofloxacin + nosihertide combination showed 50.00% sensitivity (8 isolates). Conversely, resistance was most prevalent against enrofloxacin (50.00%, 8 isolates), followed by levofloxacin (37.50%, 6 isolates). Levofloxacin also demonstrated the largest average inhibition zone (26 mm), significantly outperforming enrofloxacin (13 mm) and colistin (12 mm). These results indicate that levofloxacin has more potent antibacterial activity against biofilm forming APEC isolates, likely due to its broader spectrum and enhanced pharmacokinetics. Table (2): Antibacterial sensitivity test Isolate Levofloxacin Levofloxocine + Nosihertide Enrofloxacine Colistine # % # % # % # % Sensitive 7 43.75 8 50.00 3 18.75 9 56.25 Intermittent 3 18.75 3 18.75 5 31.25 3 18.75 Resistant 6 37.50 5 31.25 8 50.00 4 25.00 Total 16 100.00 16 100.00 16 100.00 16 100.00 1.4. Penetration of the drugs in biofilm: Among the 43 E. coli isolates, 16, 9, 18 isolates formed a strong, intermediate and weak biofilms, respectively. Levofloxacin reduced viable biofilm-embedded E. coli by 85%, Enrofloxacin achieved only a 45% reduction, and Enrofloxacin + Colistin achieved a 65% reduction. Table (3): Penetration of antibiotics in biofilm Antibiotic Initial CFU Count (CFU/ml) Final CFU Count (CFU/ml) Reduction in Biofilm Viability (%) Standard Deviation SD) Levofloxacin 1.0 x 10 6 1.5 x 10 5 85% ±0.05 Enrofloxacin 1.0 x 10 6 5.5 x 10 5 45% ±0.02 Enrofloxacin + Colistin 1.0 x10 6 3.5 x 10 5 65% ±0.03 2. In-Vivo studies: 2.1. Growth performance parameters Chickens treated with Levofloxacin achieved the highest BW and BWG by the end of the study period, with a marked difference compared to those in the Enrofloxacin and Enrofloxacin + Colistin groups. Chickens in the Levofloxacin-treated group consumed feed at a rate comparable to or slightly higher than the other groups during weeks three and four. The FCR for the Levofloxacin group remained lower than that of both Enrofloxacin and Enrofloxacin + Colistin groups throughout the study. This lower FCR indicates that the Levofloxacin group needed less feed per unit of body weight gain, suggesting better nutrient absorption and metabolic efficiency (table 4). The Levofloxacin-treated group had a lower mortality rate overall (3.33%), especially notable during the later weeks of the study when the disease effects typically peak in untreated or poorly treated cases. The positive control group had the highest mortality rate (23.33%), demonstrating the impact of colibacillosis without effective antibiotic intervention. Levofloxacin’s lower mortality rate further supports its efficacy over Enrofloxacin (6.67%). Table (4) Effect of levofloxacin (7 mg/kg B.W.), enrofloxacin (10 mg /kg B.W.) and enrofloxacin + colistin (10 mg/kg B.W. and 500 000 IU/Kg B.W., respectively) treatments for 5 successive days on growth performance parameters in broilers experimentally infected with E. coli O2 strain (9.0 × 108 CFU/ml). (Mean ± SEM) (n=30) Parameters Week Groups -ve control +ve control Levofloxacin Enrofloxacin Enrofloxacin + Colistin 1 2 3 4 5 Body Weight DOC 44.1± 0.80a 44.9±0.73a 45.05 ±0.63a 44.55±0.54a 42.6±0.65a Body Weight 1 201.35±5.28a 195.15±5.40a 194.35±4.34a 203.2±4.42a 200.5±3.26a Body Weight 2 552±10.29a 552.64±10.33a 566.83±7.75a 558±7.04a 559.29±8.85a Body Weight 3 1110.27±15.46a 845.24±20.74b 1139.63±16.66a 1098.55±14.48a 1100.63±19.45a Body Weight 4 1720.27±16.81a 1192.18±21.35c 1710.75±25.79a 1520.55±23.02b 1439.63±33.18b Body Weight 5 2520.18±28.67a 1640.25±11.78c 2505.42±36.38a 2170.64±42.45b 2100.54±32.34b Cumulative Feed intake 3460.99±11.24a 3270.94±8.25b 3521.89±13.27a 3479.39±8.74a 3281.40±9.75b Cumulative Body gain 2476.08±15.33a 1595.35±7.34c 2460.37±12.44a 2126.09±14.24b 2057.94±13.55b Cumulative FCR 1.40±0.07c 2.05±0.08a 1.43±0.04c 1.64±0.08b 1.59±0.06b Means with different superscripts in the same rows are significantly different at (P ≤ 0.05) level. Hematological parameters The Levofloxacin-treated group showed stable hematological parameters indicative of a more balanced immune response compared to those treated with Enrofloxacin, which showed slightly elevated WBCs on day 21 and 28, potentially indicating mild inflammatory responses (table 5). Table (5) Effect of levofloxacin (7 mg/kg B.W.), enrofloxacin (10 mg /kg B.W.) and enrofloxacin + colistin (10 mg/kg B.W. and 500 000 IU/Kg B.W., respectively) treatments for 5 successive days on hematological parameters in broilers experimentally infected with E. coli O2 strain (9.0 × 108 CFU/ml). (Mean ± SEM) (n=30) Parameters Age (days) Groups -ve control +ve control Levofloxacin Enrofloxacin Enrofloxacin + Colistin 1 2 3 4 5 RBC 21 2.63± 0.17 a 2.55± 0.19 a 2.58± 0.10 a 2.51± 0.13 a 2.63± 0.11 a 28 2.33± 0.18 a 2.52± 0.06 a 2.84± 0.09 a 2.77± 0.11 a 2.4± 0.11 a 35 2.5± 0.08 a 2.67± 0.15 a 2.31± 0.10 a 2.75± 0.17 a 2.61± 0.19 a WBC 21 20.58± 0.68 b 32.18± 0.31 a 19.28± 0.83 b 28.58± 0.72 a 30.52± 0.66 a 28 21.14± 0.51 b 36± 0.70 a 22.2± 0.42 b 30.3± 1.39 a 32.53± 0.95 a 35 20.42± 0.64 a 26.45± 0.74 a 21.58± 0.68 a 25.22± 0.47 a 24.08± 0.49 a Hb 21 7.28± 0.74 a 7.22± 0.53 a 7.81± 0.71 a 7.55± 0.33 a 7.63± 0.41 a 28 9.4± 0.25 a 9.82± 0.43 a 10.57± 0.31 a 9.97± 0.37 a 9.84± 0.22 a 35 11.7± 0.44 a 9.62 **± 0.55a 10.15 *± 0.31 a 10.25 *± 0.20 a 11.26± 0.40 a PCV 21 22.36± 0.99 a 22.36± 0.99 a 22.36± 0.99 a 22.36± 0.99 a 22.36± 0.99 a 28 41.6± 1.63 a 40.3± 1.28 a 42.6± 1.65 a 38± 1.41 a 47± 1.41 a 35 34.68± 1.56 a 36.3± 1.33 a 37.3± 0.60 a 38± 1.57 a 34.66± 0.20 a Means with different superscripts in the same rows are significantly different at (P ≤ 0.05) level. Biochemical parameters The Levofloxacin-treated group showed a significant decrease in AST and ALT levels, suggesting reduced liver stress and toxicity, compared with the enrofloxacin-treated groups. The Enrofloxacin-treated group showed a significant increase in serum uric acid and creatinine levels (Table 6) Table (6) Effect of levofloxacin (7 mg/kg B.W.), enrofloxacin (10 mg /kg B.W.) and enrofloxacin + colistin (10 mg/kg B.W. and 500 000 IU/Kg B.W., respectively) treatments for 5 successive days on some biochemical parameters in broilers experimentally infected with E. coli O2 strain (9.0 × 108 CFU/ml). (Mean ± SEM) (n=30) Parameters Age (days) Groups -ve control +ve control Levofloxacin Enrofloxacin Enrofloxacin + Colistin 1 2 3 4 5 AST 21 43.15± 1.99 b 84.12± 7.51 a 43.6± 2.57 b 75.53± 2.61 a 73.88± 5.15 a 28 52.00± 0.61 b 83.1± 6.43 a 50.9± 3.40 b 81± 3.35 a 80.9± 6.36 a 35 54.3± 0.30 b 85.07± 5.38 a 53.59± 3.12 b 83.49± 5.17 a 78.59± 4.34 a ALT 21 22.08± 1.37 b 66.79± 3.77 a 26.1± 1.44 b 52.23± 1.35 a 50.54± 1.73 a 28 26.29± 1.13 b 68.92± 2.16 a 25.99± 1.29 b 55.75± 0.25 a 56.76± 0.18 a 35 26.74± 1.41 b 62.54± 3.14 a 29.06± 1.29 b 55.96± 0.35 a 57.38± 0.12 a Serum Uric Acid 21 8.15± 0.21 b 8.11± 0.11 b 8.45± 0.56 b 18.23± 0.24 a 19.05± 0.44 a 28 9.59± 0.08 b 9.85± 0.09 b 9.8± 0.06 b 19.66± 0.05 a 19.86± 0.04 a 35 10.12± 0.08 b 10.72± 0.17 b 10.43± 0.06 b 21.41± 0.05 a 20.73± 0.12 a Serum Creatinine 21 0.22± 0.003 b 0.26± 0.005 b 0.25± 0.007 b 1.21± 0.08 a 1.24± 0.05 a 28 0.31± 0.007 b 0.33± 0.009 b 0.29± 0.009 b 1.3± 0.08 a 1.33± 0.07 a 35 0.33± 0.009 b 0.35± 0.007 b 0.32± 0.005 b 1.34± 0.07 a 1.35± 0.06 a Means with different superscripts in the same rows are significantly different at (P ≤ 0.05) level. Oxidative stress parameters : The Levofloxacin-treated group showed a significant decrease in MDA levels compared with the Enrofloxacin-treated groups. Therefore, Levofloxacin may induce less oxidative damage in tissues. The Levofloxacin-treated group showed a significant increase in SOD and GSH levels compared to the Enrofloxacin-treated groups. These may indicate that levofloxacin has a more robust antioxidant effect and reduces oxidative stress (table 7) Table (7) Effect of levofloxacin (7 mg/kg B.W.), enrofloxacin (10 mg /kg B.W.) and enrofloxacin + colistin (10 mg/kg B.W. and 500 000 IU/Kg B.W., respectively) treatments for 5 successive days on some oxidative stress parameters in broilers experimentally infected with E. coli O2 strain (9.0 × 108 CFU/ml). (Mean ± SEM) (n=30) Parameters Age (days) Groups -ve control +ve control Levofloxacin Enrofloxacin Enrofloxacin + Colistin 1 2 3 4 5 MDA 21 7.82± 0.10 b 9.95± 0.32 a 7.20± 0.72 b 9.15± 0.29 a 9.22± 0.37 a 28 6.25± 0.44 b 7.50± 0.69 a 6.85± 0.86 b 6.87± 0.69 a 7.10± 0.29 a 35 5.42± 0.10 b 6.88± 0.10 a 5.57± 0.30 b 6.31± 0.15 a 6.43± 0.10 a SOD 21 80.39 ± 7.33 a 46.72 ± 2.76 b 68.79 ± 5.58 ab 45.22 ± 2.16 b 52.42 ± 1.76 b 28 77.29±8.75 a 47.78±6.17 b 85.68 ± 4.24 a 49.66 ± 3.34 b 57.81 ± 4.71 b 35 53.61 ± 0.02 a 39.28 ± 1.18 b 57.10 ± 4.41 a 45.63 ± 2.11 b 49.82 ± 2.81 b GSH 21 5.12 ± 0.34 a 3.88 ± 0.06 c 4.62 ± 0.13 a 4.18 ± 0.32 b 4.10 ± 0.15 b 28 5.17 ± 0.27 a 3.36 ± 0.20 c 4.70 ± 0.06 a 4.66 ± 0.09 ab 4.54 ± 0.28 ab 35 5.44 ± 0.19 a 4.03 ± 0.12 c 5.66 ± 0.10 a 5.32 ± 0.08 b 5.27 ± 0.11 b Means with different superscripts in the same rows are significantly different at (P ≤ 0.05) level. Microbiological Efficacy On day 21, samples from the Levofloxacin group showed a lower bacterial count than those from the Enrofloxacin groups, indicating that Levofloxacin was more effective against APEC (Table 8) Table (8) Effect of levofloxacin (7 mg/kg B.W.), enrofloxacin (10 mg /kg B.W.) and enrofloxacin + colistin (10 mg/kg B.W. and 500 000 IU/Kg B.W., respectively) treatments for 5 successive days on the incidence of E. coli infection in different organs of broilers experimentally infected with E. coli O2 strain (9.0 × 10 8 CFU/ml) at the 14 th day old. (Mean ± SEM) (n=30) Group Bone Marrow Liver Kidney Spleen Lungs # % # % # % # % # % -ve Control 0 0 0 0 0 0 0 0 0 0 +ve Control 4 80 5 100 4 80 5 100 3 60 Levofloxacin 1 20 1 20 1 20 1 20 1 20 Enrofloxacin 2 40 3 60 2 40 3 60 2 40 Enrofloxacin+ Colistin 2 40 2 40 2 40 2 40 1 20 (#) = number of positive samples out of five. (%) = percentage of positive samples. The samples were collected post-treatment on the 21 st day of age. Discussion This study investigated the comparative effects of Levofloxacin and Enrofloxacin in broilers infected with avian pathogenic Escherichia coli (APEC), with particular focus on growth performance, mortality rate, health parameters, and biochemical and oxidative stress markers. The findings indicate that Levofloxacin offers several advantages over Enrofloxacin, suggesting its superiority as an antimicrobial agent in managing colibacillosis in broilers. The in vitro susceptibility profile underscores the superior antibacterial potency of levofloxacin over enrofloxacin against biofilm forming E.coli isolates. Our findings show that levofloxacin achieved a sensitivity rate of 43.75% among strong biofilm producers, nearly double that of enrofloxacin (18.75%). This aligns with the significantly larger inhibition zones observed for levofloxacin (26 mm vs. 13 mm for enrofloxacin), reinforcing its enhanced in vitro efficacy. The higher resistance observed against enrofloxacin (50.00%) compared to levofloxacin (37.50%) may reflect increasing resistance to second generation fluoroquinolones in poultry environments, as noted in previous surveillance studies [ 25 ]. These results support the pharmacological rationale for considering levofloxacin as a more effective alternative for managing colibacillosis, particularly in infections involving biofilm forming strains [ 26 ]. Levofloxacin reduced viable biofilm-embedded E. coli by 85%, Enrofloxacin achieved only a 45% reduction, and Enrofloxacin + Colistin achieved a 65% reduction. These results are consistent with the work conducted by Ishida et al. [ 27 ], which indicates the important function of levofloxacin in treating infectious diseases associated with biofilm-forming bacteria. Levofloxacin-treated chickens showed significantly higher body weight gain (BWG) and a more efficient feed conversion ratio (FCR) than those treated with Enrofloxacin. These findings align with prior research that associates Levofloxacin with improved nutrient utilization and enhanced growth outcomes. These effects may be attributed to Levofloxacin’s pharmacokinetic properties, including improved tissue penetration and a longer half-life, which enhance the bactericidal effect and reduce the persistence of infection [ 28 ]. The mortality rate was notably lower in the Levofloxacin group than in the Enrofloxacin groups, reinforcing the antibiotic’s effectiveness in managing colibacillosis, especially as disease severity escalated. This reduced mortality can be attributed to Levofloxacin’s more extensive antibacterial activity, providing effective coverage against Gram-negative bacteria like APEC, a critical feature in high-density poultry farming environments where bacterial resistance and infection spread are pressing concerns [ 29 ]. Hematological examination revealed that broilers treated with levofloxacin maintained relatively stable RBC counts, Hb concentration, and PCV throughout the experimental period, with no statistically significant deviations from the negative control group. In contrast, the positive control group and enrofloxacin-treated groups showed notable elevations in total WBC counts, particularly on days 21 and 28 post-infection. The elevated WBC counts observed in the untreated infected group reflect an active systemic inflammatory and immune response triggered by APEC infection, consistent with the septicemic nature of colibacillosis. Similar leukocytosis in E. coli –infected broilers has been previously reported and is considered a hallmark of acute bacterial infection and endotoxemia [ 30 , 31 ].The persistence of relatively higher WBC counts in the enrofloxacin and enrofloxacin–colistin groups suggests a slower or less complete resolution of infection-associated inflammation compared with levofloxacin. The comparatively normalized WBC counts observed in the levofloxacin-treated group indicate more effective bacterial clearance and reduced systemic inflammatory stimulation. This finding agrees with Varia et al. [ 32 ], who reported that third-generation fluoroquinolones exert a more balanced immunological impact in poultry, limiting excessive leukocytic responses while maintaining host defense. RBC, Hb, and PCV values did not differ significantly among treated groups, suggesting that neither levofloxacin nor enrofloxacin induced anemia or hematopoietic suppression at the administered therapeutic doses. However, Mostafa [ 29 ] reported mild reductions in RBC and Hb on days 5 and 7 post-treatment by levofloxacin, and these values normalized by day 9. This underscores the necessity of strictly following the levofloxacin dosage to prevent alterations in hematological parameters. Levofloxacin-treated birds exhibited significantly lower ALT and AST activities compared to the enrofloxacin-treated groups across all sampling periods. These findings indicate reduced hepatocellular stress and improved hepatic integrity in levofloxacin-treated broilers. While enrofloxacin is effective against E. coli, it may exert a greater hepatic metabolic burden or slower resolution of infection-related liver damage. These results align with the observations made by Varia et al. [ 32 ], which indicated that birds treated with levofloxacin exhibited normal levels of ALT and AST activities. Serum uric acid and creatinine levels were significantly elevated in enrofloxacin-treated groups compared with levofloxacin-treated birds and controls. Elevated uric acid and creatinine concentrations are indicative of renal stress or impaired glomerular filtration, which may result from drug-induced nephrotoxicity or systemic inflammatory damage [ 33 ]. The relatively stable renal biomarkers observed in the levofloxacin group suggest better renal tolerance and reduced nephrotoxic risk. This result is consistent with the conclusions drawn by Varia et al. [ 32 ], which indicated that broilers treated with levofloxacin exhibited normal renal functions. Conversely, some studies have reported minimal biochemical differences between enrofloxacin and levofloxacin when administered at lower doses or for shorter durations. These discrepancies may be attributed to differences in experimental design, infection severity, dosage regimens, and duration of exposure, emphasizing the importance of context when interpreting fluoroquinolone safety data. Oxidative stress is a key pathological consequence of APEC infection and contributes to tissue damage and disease severity in broilers. In the present study, oxidative stress markers differed markedly among treatment groups, highlighting the influence of antimicrobial choice on redox balance during colibacillosis. Broilers in the positive control group exhibited significantly increased malondialdehyde (MDA) levels accompanied by decreased superoxide dismutase (SOD) and reduced glutathione (GSH) activities, indicating enhanced lipid peroxidation and impaired antioxidant defenses. These findings are consistent with previous reports showing that APEC infection induces excessive reactive oxygen species (ROS) production through endotoxin-mediated inflammatory responses [ 34 ]. Levofloxacin treatment significantly reduced MDA concentrations and restored SOD and GSH levels toward normal values, suggesting effective mitigation of oxidative damage. This improvement likely reflects more efficient bacterial clearance and reduced inflammatory stimulation, resulting in lower ROS generation. Similar observations were reported by Al-Safi and Kafi [ 35 ] and Mostafa [ 29 ], who demonstrated that levofloxacin therapy was associated with improved antioxidant status in broilers affected by colibacillosis. In contrast, enrofloxacin-treated birds showed only partial normalization of oxidative stress markers, with persistently higher MDA levels and lower antioxidant enzyme activities compared with the levofloxacin group. This may be attributed to slower resolution of infection or fluoroquinolone-induced oxidative effects related to mitochondrial ROS generation, as previously described by Miao and Hu [ 36 ] and Zhang and Li [ 37 ]. The enrofloxacin–colistin combination did not confer additional antioxidant benefits and, in some cases, showed comparable or greater oxidative stress, possibly due to the known oxidative and nephrotoxic potential of colistin. Some studies have reported minimal differences between fluoroquinolones in healthy birds [ 25 , 38 ] however, such discrepancies may be explained by the absence of infection-induced oxidative stress in those models. Under infectious challenge, the present findings indicate that levofloxacin provides superior protection against oxidative damage compared with enrofloxacin. Overall, the oxidative stress results suggest that levofloxacin not only effectively controls APEC infection but also preserves antioxidant defenses and limits lipid peroxidation, contributing to improved tissue integrity and recovery in broiler chickens. On day 21, samples from the Levofloxacin group showed a lower bacterial count than those from the Enrofloxacin groups, indicating that Levofloxacin was more effective against APEC. This finding is supported by the work of Noviello et al. [ 26 ] which indicated that Levofloxacin achieved 99.9% reduction of E. coli after 6 hours at its MIC, highlighting its potent bactericidal effects. Alawkally and Al-Saadi [ 39 ] demonstrated that Levofloxacin exhibited considerable sensitivity against various bacterial pathogens, including E. coli, resulting in markedly reduced bacterial survival in comparison to other fluoroquinolones. This underscores the superior efficacy of Levofloxacin against APEC when contrasted with Enrofloxacin. Conclusion The study findings strongly suggest that Levofloxacin is more effective than Enrofloxacin in treating colibacillosis in broiler chickens. Levofloxacin treatment resulted in greater body weight gain, improved feed conversion, lower mortality rates, and enhanced overall health compared to Enrofloxacin. Additionally, Levofloxacin demonstrated better biochemical stability and less oxidative stress in treated chickens, suggesting a more favorable safety profile. The enhanced microbiological efficacy of Levofloxacin further supports its role as a viable therapeutic option for managing colibacillosis, contributing to improved animal welfare and productivity. Declarations Data availability The data sets spent and/or analyzed during this study are available from the corresponding author upon reason able request. Author contributions Ali M. Asy contributed to the study design and assisted in data interpretation and manuscript revision. Amany O. Selim participated in collection of samples and isolation and identification of E. coli Penetration of the drugs in biofilm. Dalia M. Azab assisted in study the animal experiments, data collection and Hematological parameters. Eman A. Abozeid contributed to Growth performance parameters, Oxidative stress parameters and critical revision of the manuscript. Mona A. Elkholy contributed to Biochemical parameters, statistical analysis and interpretation of results. Marionete Z. Nasif contributed to Antibacterial sensitivity testand critically reviewed the manuscript. Gehan El-Saied assisted in data analysis and manuscript editing. All authors reviewed and approved the final manuscript. Funding This research received no external funding. Competing interests The authors declare no competing interests. References Kim, Y. B. et al. Molecular characterization of avian pathogenic Escherichia coli from broiler chickens with colibacillosis. Poult. Sci. 99 , 1088–1095 (2020). Ren, L. et al. Supplemental xylooligosaccharide attenuates growth retardation and intestinal damage in broiler chickens challenged by avian pathogenic Escherichia coli . Agriculture 14 , 1684 (2024). Jiang, X., Yu, T., Wu, N., Meng, H. & Shi, L. Detection of qnr, aac(6′)-Ib-cr and qepA genes in Escherichia coli isolated from cooked meat products in Henan, China. Int. J. Food Microbiol. 187 , 22–25 (2014). Kathayat, D., Lokesh, D., Ranjit, S. & Rajashekara, G. Avian pathogenic Escherichia coli (APEC): An overview of virulence and pathogenesis factors, zoonotic potential, and control strategies. Pathogens 10 , 467 (2021). Juricova, H., Matiasovicova, J., Kubasova, T., Cejkova, D. & Rychlik, I. The distribution of antibiotic resistance genes in chicken gut microbiota commensals. Sci. Rep. 11 , 1–10 (2021). Seo, K. W. & Lee, Y. J. Molecular characterization of fluoroquinolone-resistant Escherichia coli from broiler breeder farms. Poult. Sci. 100 , 101250 (2021). Mahmud, S., Nazir, K. H. M. N. H. & Rahman, M. T. Prevalence and molecular detection of fluoroquinolone-resistant genes (qnrA and qnrS) in Escherichia coli isolated from healthy broiler chickens. Vet. World . 11 , 1720–1724 (2018). Hricová, M. et al. Quinolone-resistant Escherichia coli in poultry farming. Cent. Eur. J. Public. Health . 25 , 163–167 (2017). Temmerman, R. et al. Enrofloxacin dose optimization for the treatment of colibacillosis in broiler chickens using a drinking behaviour pharmacokinetic model. Antibiotics 10 , 604 (2021). Pham, T. D. M., Ziora, Z. M. & Blaskovich, M. A. T. Quinolone antibiotics. MedChemComm 10, 1719–1739 (2019). Markey, B., Leonard, F., Archambault, M., Cullinane, A. & Maguire, D. Clinical Veterinary Microbiology (E-book (Elsevier Health Sciences, 2013). Pramodhini, S., Niveditha, S., Umadevi, S., Kumar, S. & Stephen, S. Antibiotic resistance pattern of biofilm-forming uropathogens isolated from catheterized patients in Pondicherry, India. Aust Med. J. 5 , 344–348 (2012). Seddiek, S. A., Mobarak, M. G., Ali, M. M. A. & Metwaly, A. M. Potentiation of salinomycin anticoccidial effect with butylated hydroxy toluene (BHT) in broilers. Suez Canal Vet. Med. J. XIII , 241–258 (2008). Brooks, M. B., Harr, K. E., Seelig, D. M., Wardrop, K. J. & Weiss, D. J. Schalm’s Veterinary Haematology 7th edn (Wiley-Blackwell, 2022). Dein, F. J. Hematology in Clinical Avian Medicine and Surgery. In Hematology in Clinical Avian Medicine and Surgery (WB Saunders, Philadelphia, 174–191. (1984). Varliy, H. Clinical chemistry methodologies: historical perspectives and contemporary practices. Annals Clin. Chem. 11 , 161–163 (1974). Haisman, P. & Muller, B. P. Glossary of Clinical Chemistry and Terms pp. 126–154 (Butterworth, 1977). Henry, R. J. Clinical Chemistry, Principles and Techniques 2nd edn, p. 525 (Harper & Row, 1974). Ohkawa, H., Ohishi, W. & Yagi, K. Assay for lipid peroxides in animal tissues by thiobarbituric acid reaction. Anal. Biochem. 95 , 351–358 (1979). Nishikimi, M., Roa, N. A. & Yogi, K. The occurrence of superoxide anion in the reaction of reduced phenazine methosulfate and molecular oxygen. Biochem. Biophys. Res. Commun. 46 , 849–854 (1972). Beutler, E., Duron, O. & Kelly, M. B. J. A method for the determination of blood glutathione. J. Lab. Clin. Med. 61 , 882 (1963). Quinn, P. J., Markey, B. K., Carter, M. E., Donnelly, W. J. C. & Leonard, F. C. Veterinary Microbiology and Microbial Diseases 1st edn (Iowa State University Press, Blackwell Science, 2002). Duncan, D. B. Multiple range and multiple F tests. Biometrics 11 , 1–42 (1955). Snedecor, G. W. & Cochran, W. G. Statistical Methods 8th edn (Iowa University, 1989). Ringenier, M. et al. Mapping the spread of fluoroquinolone resistance: Continued presence of non-susceptible Escherichia coli in broilers. Front. Vet. Sci. 12 , 1610997 (2025). Noviello, S., Ianniello, F., Leone, S. & Esposito, S. Comparative in vitro bacteriostatic and bactericidal activity of levofloxacin and ciprofloxacin against urinary tract pathogens determined by MIC, MBC, time-kill curves, and bactericidal index analysis. Le Infezioni Med. 10 , 100–106 (2002). Ishida, H. et al. In vitro and in vivo activities of levofloxacin against biofilm-producing Pseudomonas aeruginosa . Antimicrob. Agents Chemother. 42 , 1641–1645. https://doi.org/10.1128/AAC.42.7.1641 (1998). Hossain, M. E. & Bhuiyan, M. K. J. Comparative effects of enrofloxacin and levofloxacin on growth performance and feed efficiency in broiler chickens. Int. J. Poult. Sci. 17 , 245–251 (2018). Mostafa, A. E. A. Pharmacological evaluation of levofloxacin residue depletion and hemato-biochemical alterations in broiler chickens using a validated HPLC method. Sci. Rep. 15 , 32496. https://doi.org/10.1038/s41598-025-17575-0 (2025). Hu, J. et al. Characteristics, pathogenic mechanism, zoonotic potential, drug resistance, and prevention of avian pathogenic Escherichia coli (APEC). Front. Microbiol. 13 , 1049391 (2022). Meng, J. et al. The synergy effect of matrine and berberine hydrochloride on treating colibacillosis caused by an avian highly pathogenic multidrug-resistant Escherichia coli . Poult. Sci. 103 , 104151 (2024). Varia, R. D. et al. Evaluation of levofloxacin safety in broiler chickens. Indian Vet. J. 89 , 54–56 (2012). Sureshkumar, V., Sarathchandra, G. & Ramesh, J. Biochemical, histopathological and ultrastructural profile after pulsed water medication of enrofloxacin in broiler chickens. Vet. World . 6 , 668–673 (2013). Yu, L. et al. The transcription factor YbdO attenuates the pathogenicity of avian pathogenic Escherichia coli by regulating oxidative stress response. BMC Microbiol. 24 , 544. https://doi.org/10.1186/s12866-024-03715-5 (2024). Al-Safi, S. M. M. & Kafi, L. A. Comparative study of the clinical effects of levofloxacin and spiramycin on induced colibacillosis in broiler chickens. Kufa J. Vet. Med. Sci. 8 , 63–72 (2017). Miao, Y. & Hu, D. Effects of fluoroquinolone usage on liver and kidney function in poultry. Poult. Sci. 98 , 4821–4828 (2019). Zhang, X. & Li, J. Fluoroquinolones and oxidative stress: A comparative study in poultry. Vet. Pharmacol. Toxicol. 59 , 185–192 (2020). Vougat Ngom, R. et al. A systematic review and meta-analysis on the efficacy of antibiotic treatment in controlling colibacillosis in broiler production. PLoS One . 20 , e0326535. https://doi.org/10.1371/journal.pone.0326535 (2025). Alawkally, N. A. & Al-Saadi, H. A. Antibiotic sensitivity of common bacterial pathogens against levofloxacin. Int. J. Appl. Dent. Sci. 8 , 186–190. https://doi.org/10.22271/oral.2022.v8.i3a.1572 (2022). Additional Declarations No competing interests reported. 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Asy","email":"","orcid":"","institution":"Agricultural Research Center (Animal health research institute)","correspondingAuthor":false,"prefix":"","firstName":"Ali","middleName":"M.","lastName":"Asy","suffix":""},{"id":605243425,"identity":"77f22f48-8fa7-4d14-bd2e-59e1da07e05b","order_by":1,"name":"Amany O. Selim","email":"","orcid":"","institution":"Agricultural Research Center (Animal health research institute)","correspondingAuthor":false,"prefix":"","firstName":"Amany","middleName":"O.","lastName":"Selim","suffix":""},{"id":605243427,"identity":"abe7b0f4-1ea5-43b9-9ffb-2eb03ba0731d","order_by":2,"name":"Dalia M. Azab","email":"","orcid":"","institution":"Agricultural Research Center (Animal health research institute)","correspondingAuthor":false,"prefix":"","firstName":"Dalia","middleName":"M.","lastName":"Azab","suffix":""},{"id":605243430,"identity":"d313d7ef-a0b2-4e5b-94b9-413f8203e980","order_by":3,"name":"Eman A. Abozeid","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA+UlEQVRIiWNgGAWjYBAC+wYgwQgimBkMHwAZPAS1GDAgtBgbkKiFgcFMAsogoEXs8LMHP3fY2POzM2+r+LnjngwD/+JjEgwVtTi12EunmRv2nkljlmxmK7vZe6aYh0HiWZoEw5njuG2RTjCT4G07zGZwmMfsBm9bAlDLGaCn2o7h0ZL+TfJv22Eee6CWwr9wLf/wackxkwbaImHAzGPGDLaFvwcU2jX4tJRJy55JM5A4zFYsLQvUwibBlvgg4dgB3N6fnb5N8i0oxPoPb/z4ti3Bnp//8IEDH2rqcGrBBGwSCQwMCQyHSdDCwA92Eym2jIJRMApGwTAHANyETZaPjhsEAAAAAElFTkSuQmCC","orcid":"","institution":"Agricultural Research Center (Animal health research institute)","correspondingAuthor":true,"prefix":"","firstName":"Eman","middleName":"A.","lastName":"Abozeid","suffix":""},{"id":605243432,"identity":"b8a71ed2-e542-404a-ad35-5ed05865f7ab","order_by":4,"name":"Mona A. 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Nassif","email":"","orcid":"","institution":"Agricultural Research Center (Animal health research institute)","correspondingAuthor":false,"prefix":"","firstName":"Marionette","middleName":"Z.","lastName":"Nassif","suffix":""},{"id":605243437,"identity":"0380061c-e110-46b7-95c8-370d332d8fb0","order_by":6,"name":"Gehan El-Saied","email":"","orcid":"","institution":"Agricultural Research Center (Animal health research institute)","correspondingAuthor":false,"prefix":"","firstName":"Gehan","middleName":"","lastName":"El-Saied","suffix":""}],"badges":[],"createdAt":"2026-02-04 20:38:38","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8790151/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8790151/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":104782534,"identity":"de0f105d-df80-4c06-96c5-2ea0883c2147","added_by":"auto","created_at":"2026-03-17 07:57:28","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1147094,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8790151/v1/ec8d3254-41d1-455a-88df-3f26ce4cd78c.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Comparative Efficacies Of Current Second And Third Generation Fluoroquinolone Antibiotics On Systemic Escherichia Coli In Broiler Chickens In Qalyubia Farms","fulltext":[{"header":"Introduction","content":"\u003cp\u003eColibacillosis, primarily caused by avian pathogenic Escherichia coli (APEC), is a significant bacterial infection affecting broiler chickens, leading to high mortality rates and substantial economic losses in the Middle East and the global poultry industry. The infection can disseminate to internal organs, leading to conditions such as septicemia, peritonitis, and air sacculitis [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Beyond its impact on animal health, APEC, a member of the Enterobacteriaceae family, poses a potential zoonotic risk. Although considered a commensal organism in humans and animals, it is frequently used as an indicator of enteric pathogen presence [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Some strains of avian pathogenic Escherichia coli exhibit genetic similarities to human extraintestinal pathogenic E. coli, including uropathogenic E. coli and neonatal meningitis E. coli. This genetic resemblance suggests that APEC may have the potential to cause infections in humans, such as urinary tract infections and meningitis [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. APEC's capacity to spread antimicrobial resistance genes through horizontal gene transfer poses a serious threat to both animal and human health. Effective control requires improved biosecurity measures in poultry farming, prudent use of antibiotics, and continuous monitoring of resistant strains [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eFluoroquinolones (FQ) are synthetic bactericidal agents having a bicyclic core structure related to 4-quinolone, widely used in both human and veterinary medicine to treat a variety of serious bacterial infections. They are particularly effective against Escherichia coli and other Gram-negative bacteria [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. In poultry, FQ have been widely employed to manage avian colibacillosis [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. FQ exert their antibacterial effects by disrupting bacterial DNA synthesis, leading to cell death by inhibiting topoisomerase enzymes\u0026mdash;specifically DNA gyrase (topoisomerase II) in Gram-negative bacteria and topoisomerase IV in Gram-positive microorganisms. These enzymes play critical roles in DNA replication and transcription [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eEnrofloxacin, a second-generation fluoroquinolone, has been extensively utilized in veterinary medicine for the treatment of colibacillosis; however, its use has come under scrutiny due to rising concerns regarding antimicrobial resistance (AMR) and regulatory restrictions imposed by health authorities like the European Medicines Agency (EMA) [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Consequently, there is an urgent need to explore alternative therapeutic agents that can effectively manage colibacillosis while minimizing the risk of resistance development. Levofloxacin, the L-enantiomer of ofloxacin, is a third-generation fluoroquinolone that exhibits a broader spectrum of activity and an improved pharmacokinetic profile, including near-total oral bioavailability [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Consequently, it emerges as a promising candidate for treating infections caused by APEC.\u003c/p\u003e \u003cp\u003eThis study aims to evaluate the susceptibility of Escherichia coli strains, isolated from broiler chickens\u0026rsquo; farms in Qalyubia, Egypt, to clinically relevant fluoroquinolones, enrofloxacin (second generation) and levofloxacin (third generation), to determine the prevalence of fluoroquinolone-resistant E.coli. Additionally, it aims to conduct a comparative study of the clinical effects of Levofloxacin and Enrofloxacin in broiler chickens experimentally infected with APEC. By evaluating treatment outcomes, this study seeks to provide valuable insights into optimizing therapeutic protocols for managing colibacillosis in poultry. Furthermore, understanding the differential impacts of these two fluoroquinolones may contribute to better stewardship practices in veterinary medicine and help mitigate the challenges posed by antimicrobial resistance.\u003c/p\u003e"},{"header":"MATERIAL AND METHODS","content":"\u003ch2\u003e1. In-Vitro Study:\u003c/h2\u003e\n\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n \u003ch2\u003e1.1. Collection of samples\u003c/h2\u003e\n \u003cp\u003eA total of 155 samples (liver, heart, and lungs) were collected from freshly dead and septicemic broiler chickens older than two weeks showing symptoms and postmortem lesions of colibacillosis. The samples were collected from broiler chicken farms located in various areas of Qalyoubia Governorate, Egypt, between 2024 and 2025. Appropriate permission was obtained from the farm owners prior to sample collection and conducting the research. The samples were collected in sterile tubes containing buffered peptone water and then transferred immediately to the laboratories of the Animal Health Research Institute (AHRI) in Benha city.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\n \u003ch2\u003e1.2. Isolation and identification of E. coli\u003c/h2\u003e\n \u003cp\u003eThe collected samples were initially incubated in nutrient broth at 37\u0026deg;C for 24 h. E. coli isolation was performed using selective media: Eosin Methylene Blue (EMB) agar (OXIOD) incubated at 37\u0026deg;C for 24 h, and Tryptone Bile X-glucuronide (TBX) agar (HIMEDIA) incubated at 44\u0026deg;C for 37 h. Characteristic colonies from these plates (metallic green on EMB and blue-green on TBX) were purified on tryptic soya agar for biochemical testing. The resulting pure colonies were then preserved in brain heart broth with 30% glycerol at -20\u0026deg;C for subsequent analysis (Markey et al.[\u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e] and ISO 16649-2).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\n \u003ch2\u003e1.3. Serological identification of E. coli\u003c/h2\u003e\n \u003cp\u003eThe E. coli isolates were serotyped at the Animal Health Research Institute, using \u0026quot;SEIKEN\u0026quot; polyvalent and monovalent O and K antisera (MAST ASSURE\u0026trade;), according to the method of Markey et al. [\u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e]. Briefly, a loopful of a 24-hour-old colony from nutrient agar was emulsified in physiological saline on a slide, mixed with a drop of antiserum, and observed for one minute.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\n \u003ch2\u003e1.4. Antibacterial sensitivity test\u003c/h2\u003e\n \u003cp\u003eThe disk diffusion method was applied according to CLSI 2024. The antimicrobial discs of levofloxacin, enrofloxacin, norfloxacin, colistin, and levofloxacin\u0026thinsp;+\u0026thinsp;Nosihertide were used.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n \u003ch2\u003e1.5. Biofilm Formation\u003c/h2\u003e\n \u003cp\u003eThe biofilm-forming capacity of the E. coli isolates was assessed using Congo Red Agar (CRA). Isolates that formed black colonies with a dry, crystalline consistency were classified as strong biofilm producers, while those that remained pink were considered weak producers. The assay was performed in triplicate and repeated three times independently. Edwardsiella tarda MW362141 was included as a positive control, following the methodology described by [\u003cspan class=\"CitationRef\"\u003e12\u003c/span\u003e]. E. coli biofilm production was induced on microtiter plates. After 24 hours, antibiotics were applied to the biofilm, and remaining viable cells were quantified by plating on MacConkey agar and measuring colony-forming units (CFUs). The percentage reduction in CFU counts post-treatment indicated the biofilm penetration efficacy for each antibiotic.\u003c/p\u003e\n\u003c/div\u003e\n\u003ch3\u003e2. In-Vivo Study:\u003c/h3\u003e\n\u003cp\u003e\u003cspan\u003e\u003c/span\u003e\u003c/p\u003e\n\u003cp\u003e2.1. \u003cstrong\u003eBirds\u003c/strong\u003e: A total of 150, apparently healthy, one-day-old, unsexed broiler chicks of a commercial breed (Cobb 500) were purchased from El-Watania Poultry company.\u003c/p\u003e\u003cspan\u003e\n \u003cp\u003e2.2. \u003cstrong\u003eDrugs\u003c/strong\u003e: Levofloxacin (Lexoflon OR\u0026reg;, NITA-FARM company, Russia. Each 1 ml contains 150 mg Levofloxacin). Enrofloxacin (Enroveto 20\u0026reg;, VMD company, Belgium. Each 1 ml contains 200 mg Enrofloxacin). Enrofloxacin\u0026thinsp;+\u0026thinsp;Colistin (Enronit OR\u0026reg;, NITA-FARM company, Russia. Each 1 ml contains 100 mg of Enrofloxacin\u0026thinsp;+\u0026thinsp;1000 000 IU Colistin).\u003c/p\u003e\n\u003c/span\u003e\u003cspan\u003e\n \u003cp\u003e2.3. \u003cstrong\u003eExperimental design\u003c/strong\u003e: One hundred and fifty chicks were randomly assigned to five groups, with 30 chicks in each. Group 1 served as the control negative group, consisting of non-infected, non-treated chicks. The remaining four groups were orally infected with the APEC O2 serotype strain on day 14. This serotype is one of the most common strains in the Middle East and North Africa region (MENA). The infectious dose was 0.5 ml of APEC O2 suspension per bird, containing 9.0 \u0026times; 10^8 CFU/ml. Group 2 was the control positive group, infected but untreated. Group 3 was infected and treated with Levofloxacin at 7.5 mg/kg body weight in drinking water for five consecutive days, from day 16 to day 20, which is one day after infection. Group 4 was infected and treated with Enrofloxacin at 10 mg/kg body weight in drinking water for five days from day 16 to day 20, starting one day after infection. Group 5 was infected and received a combination of Enrofloxacin and Colistin at 10 mg/kg and 500,000 IU/kg body weight, respectively, in drinking water for five consecutive days from day 16 to day 20, starting one day after infection. During the entire experiment, the chickens were fed a commercial balanced ration ad libitum and had free access to water. The feed was verified to be free of antimicrobial additives.\u003c/p\u003e\n\u003c/span\u003e\u003cspan\u003e\n \u003cp\u003e2.4. \u003cstrong\u003eGrowth performance parameters\u003c/strong\u003e: The chicks were individually marked and weighed at one day old, then body weight (BW) was recorded weekly till the end of the experiment (the fifth week). Cumulative feed consumption, cumulative body weight gains (BWG), and feed conversion ratios (FCR) were calculated [\u003cspan class=\"CitationRef\"\u003e13\u003c/span\u003e]. The mortality rate was also recorded and calculated.\u003c/p\u003e\n\u003c/span\u003e\u003cspan\u003e\n \u003cp\u003e2.5. \u003cstrong\u003eHematological parameters\u003c/strong\u003e: The blood samples were obtained from the wing vein of five birds from each group on the 21st, 28th, and 35th days of age. Each sample was divided into two portions. The first portion was collected on tubes containing EDTA and used for the determination of red blood cell (RBC), white blood cell (WBC), hemoglobin (Hb) concentration, and packed cell volume (PCV) [\u003cspan class=\"CitationRef\"\u003e14\u003c/span\u003e]. The second portion was allowed to separate the serum and kept at -20˚C [\u003cspan class=\"CitationRef\"\u003e15\u003c/span\u003e]15to determine biochemical parameters.\u003c/p\u003e\n\u003c/span\u003e\u003cspan\u003e\n \u003cp\u003e2.6. \u003cstrong\u003eBiochemical parameters\u003c/strong\u003e: The separated serum samples were used to determine the activity of serum Alanine aminotransferase (ALT), Aspartate aminotransferase (AST) [\u003cspan class=\"CitationRef\"\u003e16\u003c/span\u003e]., serum uric acid [\u003cspan class=\"CitationRef\"\u003e17\u003c/span\u003e]., and creatinine [\u003cspan class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e\n\u003c/span\u003e\u003cspan\u003e\n \u003cp\u003e2.7. \u003cstrong\u003eOxidative stress parameters\u003c/strong\u003e: Liver and kidney tissues were obtained from five birds in each group on the 21st, 28th, and 35th days of age. These samples were preserved at -20\u0026deg;C. Subsequently, the tissues were processed into 10% homogenate samples using normal saline to assess oxidative stress parameters, including Malondialdehyde (MDA) [\u003cspan class=\"CitationRef\"\u003e19\u003c/span\u003e], Superoxide Dismutase (SOD) activity [\u003cspan class=\"CitationRef\"\u003e20\u003c/span\u003e], and Reduced Glutathione GSH concentration [\u003cspan class=\"CitationRef\"\u003e21\u003c/span\u003e].\u003c/p\u003e\n\u003c/span\u003e\u003cspan\u003e\n \u003cp\u003e2.8. \u003cstrong\u003eMicrobiological Efficacy\u003c/strong\u003e: APEC was isolated from five samples per group, collected from the bone marrow, liver, kidney, spleen, and lungs, at three time points: 13, 15, and 21 days of age) [\u003cspan class=\"CitationRef\"\u003e22\u003c/span\u003e]. The initial isolation on day 13, conducted one day before challenge with the E. coli O2 strain, confirmed the absence of a natural APEC infection in all experimental birds. The subsequent isolation on day 15, one day post-challenge, verified the successful establishment of the infection. The final isolation on day 21, following the conclusion of all treatments, served to determine their microbiological efficacy.\u003c/p\u003e\n\u003c/span\u003e\n\u003cp\u003e\u003c/p\u003e\n\u003ch3\u003e2.9. Statistical analysis\u003c/h3\u003e\n\u003cp\u003eThe data were analyzed by determining the normality via the Shapiro-Wilk test. The differences between groups were analyzed by One-Way ANOVA followed by Duncan\u0026apos;s multiple comparison Post Hoc tests [\u003cspan class=\"CitationRef\"\u003e23\u003c/span\u003e]. The Statistical Package for Social Science (IBM SPSS, version 28.0, (2021); SPSS Inc., Chicago IL, USA) was used. Probability values of less than 5% (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05) were considered significant [\u003cspan class=\"CitationRef\"\u003e24\u003c/span\u003e]. Data were represented as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard error of mean (SEM).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2.10. Ethical approval and ARRIVE guidelines\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll animal experimental procedures were approved and carried out in accordance with the ethical guidelines of the Research Ethics Committee at the Animal Health Research Institute, Agriculture Research Center (ARC), Giza, Egypt. The ethical approval was granted specifically for the animal study component of the research protocol. All methods involving animals are reported in accordance with the ARRIVE guidelines (\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://arriveguidelines.org/\u003c/span\u003e\u003c/span\u003e) to ensure transparent and comprehensive reporting of animal research.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003e1. \u0026nbsp; \u0026nbsp;In-Vitro studies:\u003c/p\u003e\n\u003cp\u003e1.1. Isolation and identification of E. coli: Among the 155 samples, 43 isolates were identified as E. coli. Specifically, there were 34, 5, and 4 E. coli isolates obtained from the liver, lung, and heart, respectively.\u003c/p\u003e\n\u003cp\u003e1.2. Serological identification of E. coli: There are 16 strong biofim forming E.coli isolates. They were serotyped as in table (1).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTable (1):\u0026nbsp;Isolation and identification of the strong biofilm forming E. coli\u0026nbsp;isolates.\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"100%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 36px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eE. Coli isolate\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 31px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eNo. of isolate number\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 31px;\"\u003e\n \u003cp\u003e\u003cstrong\u003ePercentage (%)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 36px;\"\u003e\n \u003cp\u003eO2:K1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 31px;\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 31px;\"\u003e\n \u003cp\u003e37.50\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 36px;\"\u003e\n \u003cp\u003eO55:K59\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 31px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 31px;\"\u003e\n \u003cp\u003e12.50\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 36px;\"\u003e\n \u003cp\u003eO44:K74\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 31px;\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 31px;\"\u003e\n \u003cp\u003e25.00\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 36px;\"\u003e\n \u003cp\u003eO26:K60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 31px;\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 31px;\"\u003e\n \u003cp\u003e18.75\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 36px;\"\u003e\n \u003cp\u003eO114:K90\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 31px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 31px;\"\u003e\n \u003cp\u003e06.25\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 36px;\"\u003e\n \u003cp\u003eTotal\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 31px;\"\u003e\n \u003cp\u003e16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 31px;\"\u003e\n \u003cp\u003e100.00\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e1.3.\u0026nbsp;Antibacterial sensitivity test\u003c/p\u003e\n\u003cp\u003eThe in vitro sensitivity testing of 16 strong biofilm forming E. coli isolates revealed superior efficacy of levofloxacin compared to enrofloxacin. As shown in Table (2) levofloxacin exhibited the highest susceptibility rate, with 43.75% (7 out of 16) of isolates classified as sensitive, compared to only 18.75% (3 isolates) for enrofloxacin. The levofloxacin + nosihertide combination showed 50.00% sensitivity (8 isolates). Conversely, resistance was most prevalent against enrofloxacin (50.00%, 8 isolates), followed by levofloxacin (37.50%, 6 isolates). Levofloxacin also demonstrated the largest average inhibition zone (26 mm), significantly outperforming enrofloxacin (13 mm) and colistin (12 mm). These results indicate that levofloxacin has more potent antibacterial activity against biofilm forming APEC isolates, likely due to its broader spectrum and enhanced pharmacokinetics.\u003c/p\u003e\n\u003cp\u003eTable (2): Antibacterial sensitivity test\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"100%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 20px;\"\u003e\n \u003cp\u003eIsolate\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" style=\"width: 20px;\"\u003e\n \u003cp\u003eLevofloxacin\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" style=\"width: 20px;\"\u003e\n \u003cp\u003eLevofloxocine + Nosihertide\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" style=\"width: 19px;\"\u003e\n \u003cp\u003eEnrofloxacine\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" style=\"width: 19px;\"\u003e\n \u003cp\u003eColistine\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 6px;\"\u003e\n \u003cp\u003e#\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 14px;\"\u003e\n \u003cp\u003e%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 6px;\"\u003e\n \u003cp\u003e#\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 13px;\"\u003e\n \u003cp\u003e%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 6px;\"\u003e\n \u003cp\u003e#\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 12px;\"\u003e\n \u003cp\u003e%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 6px;\"\u003e\n \u003cp\u003e#\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 12px;\"\u003e\n \u003cp\u003e%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 20px;\"\u003e\n \u003cp\u003eSensitive\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 6px;\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 14px;\"\u003e\n \u003cp\u003e43.75\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 6px;\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 13px;\"\u003e\n \u003cp\u003e50.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 6px;\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 12px;\"\u003e\n \u003cp\u003e18.75\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 6px;\"\u003e\n \u003cp\u003e9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 12px;\"\u003e\n \u003cp\u003e56.25\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 20px;\"\u003e\n \u003cp\u003eIntermittent\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 6px;\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 14px;\"\u003e\n \u003cp\u003e18.75\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 6px;\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 13px;\"\u003e\n \u003cp\u003e18.75\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 6px;\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 12px;\"\u003e\n \u003cp\u003e31.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 6px;\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 12px;\"\u003e\n \u003cp\u003e18.75\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 20px;\"\u003e\n \u003cp\u003eResistant\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 6px;\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 14px;\"\u003e\n \u003cp\u003e37.50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 6px;\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 13px;\"\u003e\n \u003cp\u003e31.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 6px;\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 12px;\"\u003e\n \u003cp\u003e50.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 6px;\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 12px;\"\u003e\n \u003cp\u003e25.00\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 20px;\"\u003e\n \u003cp\u003eTotal\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 6px;\"\u003e\n \u003cp\u003e16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 14px;\"\u003e\n \u003cp\u003e100.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 6px;\"\u003e\n \u003cp\u003e16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 13px;\"\u003e\n \u003cp\u003e100.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 6px;\"\u003e\n \u003cp\u003e16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 12px;\"\u003e\n \u003cp\u003e100.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 6px;\"\u003e\n \u003cp\u003e16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 12px;\"\u003e\n \u003cp\u003e100.00\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e1.4. Penetration of the drugs in biofilm: Among the 43 E. coli isolates, 16, 9, 18 isolates formed a strong, intermediate and weak biofilms, respectively. Levofloxacin reduced viable biofilm-embedded E. coli by 85%, Enrofloxacin achieved only a 45% reduction, and Enrofloxacin + Colistin achieved a 65% reduction.\u003c/p\u003e\n\u003cp\u003eTable (3): Penetration of antibiotics in biofilm\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"624\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 167px;\"\u003e\n \u003cp\u003eAntibiotic\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eInitial CFU Count\u0026nbsp;\u003cbr\u003e\u0026nbsp;(CFU/ml)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eFinal CFU Count (CFU/ml)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003eReduction in Biofilm Viability (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 98px;\"\u003e\n \u003cp\u003eStandard Deviation SD)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 167px;\"\u003e\n \u003cp\u003eLevofloxacin\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e1.0 x 10\u003csup\u003e6\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e1.5 x 10\u003csup\u003e5\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e85%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 98px;\"\u003e\n \u003cp\u003e\u0026plusmn;0.05\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 167px;\"\u003e\n \u003cp\u003eEnrofloxacin\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e1.0 x 10\u003csup\u003e6\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e5.5 x 10\u003csup\u003e5\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e45%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 98px;\"\u003e\n \u003cp\u003e\u0026plusmn;0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 167px;\"\u003e\n \u003cp\u003eEnrofloxacin + Colistin\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e1.0 x10\u003csup\u003e6\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e3.5 x 10\u003csup\u003e5\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e65%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 98px;\"\u003e\n \u003cp\u003e\u0026plusmn;0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003e2. \u0026nbsp;\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eIn-Vivo studies:\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2.1.\u0026nbsp;Growth performance parameters\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eChickens treated with Levofloxacin achieved the highest BW and BWG by the end of the study period, with a marked difference compared to those in the Enrofloxacin and Enrofloxacin + Colistin groups. Chickens in the Levofloxacin-treated group consumed feed at a rate comparable to or slightly higher than the other groups during weeks three and four. The FCR for the Levofloxacin group remained lower than that of both Enrofloxacin and Enrofloxacin + Colistin groups throughout the study. This lower FCR indicates that the Levofloxacin group needed less feed per unit of body weight gain, suggesting better nutrient absorption and metabolic efficiency (table 4). The Levofloxacin-treated group had a lower mortality rate overall (3.33%), especially notable during the later weeks of the study when the disease effects typically peak in untreated or poorly treated cases. The positive control group had the highest mortality rate (23.33%), demonstrating the impact of colibacillosis without effective antibiotic intervention. Levofloxacin\u0026rsquo;s lower mortality rate further supports its efficacy over Enrofloxacin (6.67%).\u003c/p\u003e\n\u003cp\u003eTable (4) Effect of levofloxacin (7 mg/kg B.W.), enrofloxacin (10 mg /kg B.W.) and enrofloxacin + colistin (10 mg/kg B.W. and 500 000 IU/Kg B.W., respectively) treatments for 5 successive days on growth performance parameters in broilers experimentally infected with E. coli O2 strain (9.0 \u0026times; 108 CFU/ml). (Mean \u0026plusmn; SEM) (n=30)\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"100%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"3\" style=\"width: 13px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eParameters\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"3\" style=\"width: 6px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eWeek\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"6\" valign=\"top\" style=\"width: 80px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eGroups\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e-ve control\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003e+ve control\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003eLevofloxacin\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 2px;\"\u003e\n \u003cp\u003eEnrofloxacin\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 31px;\"\u003e\n \u003cp\u003eEnrofloxacin + Colistin\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 2px;\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 31px;\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 13px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eBody Weight\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 6px;\"\u003e\n \u003cp\u003eDOC\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e44.1\u0026plusmn; 0.80a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003e44.9\u0026plusmn;0.73a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e45.05 \u0026plusmn;0.63a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 2px;\"\u003e\n \u003cp\u003e44.55\u0026plusmn;0.54a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 31px;\"\u003e\n \u003cp\u003e42.6\u0026plusmn;0.65a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 13px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eBody Weight\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 6px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e201.35\u0026plusmn;5.28a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003e195.15\u0026plusmn;5.40a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e194.35\u0026plusmn;4.34a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 2px;\"\u003e\n \u003cp\u003e203.2\u0026plusmn;4.42a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 31px;\"\u003e\n \u003cp\u003e200.5\u0026plusmn;3.26a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 13px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eBody Weight\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 6px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e552\u0026plusmn;10.29a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003e552.64\u0026plusmn;10.33a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e566.83\u0026plusmn;7.75a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 2px;\"\u003e\n \u003cp\u003e558\u0026plusmn;7.04a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 31px;\"\u003e\n \u003cp\u003e559.29\u0026plusmn;8.85a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 13px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eBody Weight\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 6px;\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e1110.27\u0026plusmn;15.46a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003e845.24\u0026plusmn;20.74b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e1139.63\u0026plusmn;16.66a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 2px;\"\u003e\n \u003cp\u003e1098.55\u0026plusmn;14.48a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 31px;\"\u003e\n \u003cp\u003e1100.63\u0026plusmn;19.45a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 13px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eBody Weight\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 6px;\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e1720.27\u0026plusmn;16.81a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003e1192.18\u0026plusmn;21.35c\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e1710.75\u0026plusmn;25.79a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 2px;\"\u003e\n \u003cp\u003e1520.55\u0026plusmn;23.02b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 31px;\"\u003e\n \u003cp\u003e1439.63\u0026plusmn;33.18b\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 13px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eBody Weight\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 6px;\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e2520.18\u0026plusmn;28.67a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003e1640.25\u0026plusmn;11.78c\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e2505.42\u0026plusmn;36.38a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 2px;\"\u003e\n \u003cp\u003e2170.64\u0026plusmn;42.45b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 31px;\"\u003e\n \u003cp\u003e2100.54\u0026plusmn;32.34b\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 19px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eCumulative Feed intake\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e3460.99\u0026plusmn;11.24a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003e3270.94\u0026plusmn;8.25b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e3521.89\u0026plusmn;13.27a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 18px;\"\u003e\n \u003cp\u003e3479.39\u0026plusmn;8.74a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 15px;\"\u003e\n \u003cp\u003e3281.40\u0026plusmn;9.75b\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 19px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eCumulative Body gain\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e2476.08\u0026plusmn;15.33a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003e1595.35\u0026plusmn;7.34c\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e2460.37\u0026plusmn;12.44a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 18px;\"\u003e\n \u003cp\u003e2126.09\u0026plusmn;14.24b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 15px;\"\u003e\n \u003cp\u003e2057.94\u0026plusmn;13.55b\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 19px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eCumulative FCR\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e1.40\u0026plusmn;0.07c\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003e2.05\u0026plusmn;0.08a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e1.43\u0026plusmn;0.04c\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 18px;\"\u003e\n \u003cp\u003e1.64\u0026plusmn;0.08b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 15px;\"\u003e\n \u003cp\u003e1.59\u0026plusmn;0.06b\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eMeans with different superscripts in the same rows are significantly different at (P \u0026le; 0.05) level.\u003cstrong\u003e\u003cbr\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eHematological parameters\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe Levofloxacin-treated group showed stable hematological parameters indicative of a more balanced immune response compared to those treated with Enrofloxacin, which showed slightly elevated WBCs on day 21 and 28, potentially indicating mild inflammatory responses (table 5).\u003c/p\u003e\n\u003cp\u003eTable (5) Effect of levofloxacin (7 mg/kg B.W.), enrofloxacin (10 mg /kg B.W.) and enrofloxacin + colistin (10 mg/kg B.W. and 500 000 IU/Kg B.W., respectively) treatments for 5 successive days on hematological parameters in broilers experimentally infected with E. coli O2 strain (9.0 \u0026times; 108 CFU/ml). (Mean \u0026plusmn; SEM) (n=30)\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"100%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"3\" style=\"width: 0px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eParameters\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"3\" style=\"width: 0px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eAge (days)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"5\" valign=\"top\" style=\"width: 0px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eGroups\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e-ve control\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e+ve control\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003eLevofloxacin\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003eEnrofloxacin\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003eEnrofloxacin + Colistin\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"3\" valign=\"top\" style=\"width: 0px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eRBC\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 7px;\"\u003e\n \u003cp\u003e21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e2.63\u0026plusmn; 0.17 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e2.55\u0026plusmn; 0.19 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e2.58\u0026plusmn; 0.10 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e2.51\u0026plusmn; 0.13 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e2.63\u0026plusmn; 0.11 a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 7px;\"\u003e\n \u003cp\u003e28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e2.33\u0026plusmn; 0.18 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e2.52\u0026plusmn; 0.06 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e2.84\u0026plusmn; 0.09 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e2.77\u0026plusmn; 0.11 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e2.4\u0026plusmn; 0.11 a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 7px;\"\u003e\n \u003cp\u003e35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e2.5\u0026plusmn; 0.08 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e2.67\u0026plusmn; 0.15 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e2.31\u0026plusmn; 0.10 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e2.75\u0026plusmn; 0.17 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e2.61\u0026plusmn; 0.19 a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"3\" valign=\"top\" style=\"width: 0px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eWBC\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 7px;\"\u003e\n \u003cp\u003e21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e20.58\u0026plusmn; 0.68 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e32.18\u0026plusmn; 0.31 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e19.28\u0026plusmn; 0.83 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e28.58\u0026plusmn; 0.72 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e30.52\u0026plusmn; 0.66 a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 7px;\"\u003e\n \u003cp\u003e28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e21.14\u0026plusmn; 0.51 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e36\u0026plusmn; 0.70 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e22.2\u0026plusmn; 0.42 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e30.3\u0026plusmn; 1.39 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e32.53\u0026plusmn; 0.95 a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 7px;\"\u003e\n \u003cp\u003e35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e20.42\u0026plusmn; 0.64 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e26.45\u0026plusmn; 0.74 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e21.58\u0026plusmn; 0.68 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e25.22\u0026plusmn; 0.47 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e24.08\u0026plusmn; 0.49 a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"3\" valign=\"top\" style=\"width: 0px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eHb\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 7px;\"\u003e\n \u003cp\u003e21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e7.28\u0026plusmn; 0.74 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e7.22\u0026plusmn; 0.53 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e7.81\u0026plusmn; 0.71 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e7.55\u0026plusmn; 0.33 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e7.63\u0026plusmn; 0.41 a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 7px;\"\u003e\n \u003cp\u003e28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e9.4\u0026plusmn; 0.25 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e9.82\u0026plusmn; 0.43 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e10.57\u0026plusmn; 0.31 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e9.97\u0026plusmn; 0.37 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e9.84\u0026plusmn; 0.22 a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 7px;\"\u003e\n \u003cp\u003e35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e11.7\u0026plusmn; 0.44 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e9.62 **\u0026plusmn; 0.55a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e10.15 *\u0026plusmn; 0.31 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e10.25 *\u0026plusmn; 0.20 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e11.26\u0026plusmn; 0.40 a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"3\" valign=\"top\" style=\"width: 0px;\"\u003e\n \u003cp\u003e\u003cstrong\u003ePCV\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 7px;\"\u003e\n \u003cp\u003e21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e22.36\u0026plusmn; 0.99 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e22.36\u0026plusmn; 0.99 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e22.36\u0026plusmn; 0.99 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e22.36\u0026plusmn; 0.99 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e22.36\u0026plusmn; 0.99 a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 7px;\"\u003e\n \u003cp\u003e28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e41.6\u0026plusmn; 1.63 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e40.3\u0026plusmn; 1.28 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e42.6\u0026plusmn; 1.65 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e38\u0026plusmn; 1.41 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e47\u0026plusmn; 1.41 a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 7px;\"\u003e\n \u003cp\u003e35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e34.68\u0026plusmn; 1.56 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e36.3\u0026plusmn; 1.33 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e37.3\u0026plusmn; 0.60 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e38\u0026plusmn; 1.57 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e34.66\u0026plusmn; 0.20 a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eMeans with different superscripts in the same rows are significantly different at (P \u0026le; 0.05) level.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eBiochemical parameters\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe Levofloxacin-treated group showed a significant decrease in AST and ALT levels, suggesting reduced liver stress and toxicity, compared with the enrofloxacin-treated groups. The Enrofloxacin-treated group showed a significant increase in serum uric acid and creatinine levels (Table 6)\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTable (6) Effect of levofloxacin (7 mg/kg B.W.), enrofloxacin (10 mg /kg B.W.) and enrofloxacin + colistin (10 mg/kg B.W. and 500 000 IU/Kg B.W., respectively) treatments for 5 successive days on some biochemical parameters in broilers experimentally infected with E. coli O2 strain (9.0 \u0026times; 108 CFU/ml). (Mean \u0026plusmn; SEM) (n=30)\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"100%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"3\" style=\"width: 10px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eParameters\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"3\" style=\"width: 7px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eAge (days)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"5\" valign=\"top\" style=\"width: 81px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eGroups\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e-ve control\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e+ve control\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003eLevofloxacin\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003eEnrofloxacin\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003eEnrofloxacin \u0026nbsp; \u0026nbsp;+ Colistin\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"3\" valign=\"top\" style=\"width: 10px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eAST\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 7px;\"\u003e\n \u003cp\u003e21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e43.15\u0026plusmn; 1.99 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e84.12\u0026plusmn; 7.51 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e43.6\u0026plusmn; 2.57 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e75.53\u0026plusmn; 2.61 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e73.88\u0026plusmn; 5.15 a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 7px;\"\u003e\n \u003cp\u003e28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e52.00\u0026plusmn; 0.61 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e83.1\u0026plusmn; 6.43 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e50.9\u0026plusmn; 3.40 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e81\u0026plusmn; 3.35 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e80.9\u0026plusmn; 6.36 a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 7px;\"\u003e\n \u003cp\u003e35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e54.3\u0026plusmn; 0.30 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e85.07\u0026plusmn; 5.38 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e53.59\u0026plusmn; 3.12 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e83.49\u0026plusmn; 5.17 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e78.59\u0026plusmn; 4.34 a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"3\" valign=\"top\" style=\"width: 10px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eALT\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 7px;\"\u003e\n \u003cp\u003e21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e22.08\u0026plusmn; 1.37 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e66.79\u0026plusmn; 3.77 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e26.1\u0026plusmn; 1.44 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e52.23\u0026plusmn; 1.35 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e50.54\u0026plusmn; 1.73 a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 7px;\"\u003e\n \u003cp\u003e28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e26.29\u0026plusmn; 1.13 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e68.92\u0026plusmn; 2.16 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e25.99\u0026plusmn; 1.29 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e55.75\u0026plusmn; 0.25 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e56.76\u0026plusmn; 0.18 a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 7px;\"\u003e\n \u003cp\u003e35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e26.74\u0026plusmn; 1.41 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e62.54\u0026plusmn; 3.14 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e29.06\u0026plusmn; 1.29 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e55.96\u0026plusmn; 0.35 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e57.38\u0026plusmn; 0.12 a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"3\" valign=\"top\" style=\"width: 10px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSerum Uric Acid\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 7px;\"\u003e\n \u003cp\u003e21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e8.15\u0026plusmn; 0.21 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e8.11\u0026plusmn; 0.11 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e8.45\u0026plusmn; 0.56 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e18.23\u0026plusmn; 0.24 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e19.05\u0026plusmn; 0.44 a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 7px;\"\u003e\n \u003cp\u003e28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e9.59\u0026plusmn; 0.08 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e9.85\u0026plusmn; 0.09 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e9.8\u0026plusmn; 0.06 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e19.66\u0026plusmn; 0.05 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e19.86\u0026plusmn; 0.04 a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 7px;\"\u003e\n \u003cp\u003e35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e10.12\u0026plusmn; 0.08 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e10.72\u0026plusmn; 0.17 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e10.43\u0026plusmn; 0.06 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e21.41\u0026plusmn; 0.05 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e20.73\u0026plusmn; 0.12 a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"3\" valign=\"top\" style=\"width: 10px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSerum Creatinine\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 7px;\"\u003e\n \u003cp\u003e21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e0.22\u0026plusmn; 0.003 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e0.26\u0026plusmn; 0.005 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e0.25\u0026plusmn; 0.007 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e1.21\u0026plusmn; 0.08 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e1.24\u0026plusmn; 0.05 a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 7px;\"\u003e\n \u003cp\u003e28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e0.31\u0026plusmn; 0.007 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e0.33\u0026plusmn; 0.009 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e0.29\u0026plusmn; 0.009 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e1.3\u0026plusmn; 0.08 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e1.33\u0026plusmn; 0.07 a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 7px;\"\u003e\n \u003cp\u003e35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e0.33\u0026plusmn; 0.009 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e0.35\u0026plusmn; 0.007 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e0.32\u0026plusmn; 0.005 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e1.34\u0026plusmn; 0.07 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e1.35\u0026plusmn; 0.06 a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eMeans with different superscripts in the same rows are significantly different at (P \u0026le; 0.05) level.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eOxidative stress parameters\u003c/strong\u003e:\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe Levofloxacin-treated group showed a significant decrease in MDA levels compared with the Enrofloxacin-treated groups. \u0026nbsp; Therefore, Levofloxacin may induce less oxidative damage in tissues. The Levofloxacin-treated group showed a significant increase in SOD and GSH levels compared to the Enrofloxacin-treated groups. These may indicate that levofloxacin has a more robust antioxidant effect and reduces oxidative stress (table 7)\u003c/p\u003e\n\u003cp\u003eTable (7) Effect of levofloxacin (7 mg/kg B.W.), enrofloxacin (10 mg /kg B.W.) and enrofloxacin + colistin (10 mg/kg B.W. and 500 000 IU/Kg B.W., respectively) treatments for 5 successive days on some oxidative stress parameters in broilers experimentally infected with E. coli O2 strain (9.0 \u0026times; 108 CFU/ml). (Mean \u0026plusmn; SEM) (n=30)\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"100%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"3\" style=\"width: 10px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eParameters\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"3\" style=\"width: 6px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eAge (days)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"5\" valign=\"top\" style=\"width: 82px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eGroups\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e-ve control\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e+ve control\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003eLevofloxacin\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003eEnrofloxacin\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003eEnrofloxacin \u0026nbsp; \u0026nbsp;+ Colistin\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"3\" valign=\"top\" style=\"width: 10px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMDA\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 6px;\"\u003e\n \u003cp\u003e21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e7.82\u0026plusmn; 0.10\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e9.95\u0026plusmn; 0.32\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e7.20\u0026plusmn; 0.72\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e9.15\u0026plusmn; 0.29\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e9.22\u0026plusmn; 0.37\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 6px;\"\u003e\n \u003cp\u003e28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e6.25\u0026plusmn; 0.44\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e7.50\u0026plusmn; 0.69\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e6.85\u0026plusmn; 0.86\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e6.87\u0026plusmn; 0.69\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e7.10\u0026plusmn; 0.29\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 6px;\"\u003e\n \u003cp\u003e35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e5.42\u0026plusmn; 0.10\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e6.88\u0026plusmn; 0.10\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e5.57\u0026plusmn; 0.30\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e6.31\u0026plusmn; 0.15\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e6.43\u0026plusmn; 0.10\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"3\" valign=\"top\" style=\"width: 10px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSOD\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 6px;\"\u003e\n \u003cp\u003e21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e80.39 \u0026plusmn; 7.33\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e46.72 \u0026plusmn; 2.76\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e68.79 \u0026plusmn; 5.58\u003csup\u003eab\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e45.22 \u0026plusmn; 2.16\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e52.42 \u0026plusmn; 1.76\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 6px;\"\u003e\n \u003cp\u003e28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e77.29\u0026plusmn;8.75\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e47.78\u0026plusmn;6.17\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e85.68 \u0026plusmn; 4.24\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e49.66 \u0026plusmn; 3.34\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e57.81 \u0026plusmn; 4.71\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 6px;\"\u003e\n \u003cp\u003e35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e53.61 \u0026plusmn; 0.02\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e39.28 \u0026plusmn; 1.18\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e57.10 \u0026plusmn; 4.41\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e45.63 \u0026plusmn; 2.11\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e49.82 \u0026plusmn; 2.81\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"3\" valign=\"top\" style=\"width: 10px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eGSH\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 6px;\"\u003e\n \u003cp\u003e21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e5.12 \u0026plusmn; 0.34\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e3.88 \u0026plusmn; 0.06\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e4.62 \u0026plusmn; 0.13\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e4.18 \u0026plusmn; 0.32\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e4.10 \u0026plusmn; 0.15\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 6px;\"\u003e\n \u003cp\u003e28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e5.17 \u0026plusmn; 0.27\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e3.36 \u0026plusmn; 0.20\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e4.70 \u0026plusmn; 0.06\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e4.66 \u0026plusmn; 0.09\u003csup\u003eab\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e4.54 \u0026plusmn; 0.28\u003csup\u003eab\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 6px;\"\u003e\n \u003cp\u003e35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e5.44 \u0026plusmn; 0.19\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e4.03 \u0026plusmn; 0.12\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e5.66 \u0026plusmn; 0.10\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e5.32 \u0026plusmn; 0.08\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16px;\"\u003e\n \u003cp\u003e5.27 \u0026plusmn; 0.11\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eMeans with different superscripts in the same rows are significantly different at (P \u0026le; 0.05) level.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMicrobiological Efficacy\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eOn day 21, samples from the Levofloxacin group showed a lower bacterial count than those from the Enrofloxacin groups, indicating that Levofloxacin was more effective against APEC\u0026nbsp;(Table 8)\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTable (8) Effect of levofloxacin (7 mg/kg B.W.), enrofloxacin (10 mg /kg B.W.) and enrofloxacin + colistin (10 mg/kg B.W. and 500 000 IU/Kg B.W., respectively) treatments for 5 successive days on the incidence of E. coli infection in different organs of broilers experimentally infected with E. coli O2 strain (9.0 \u0026times; 10\u003csup\u003e8\u003c/sup\u003e CFU/ml) at the 14\u003csup\u003eth\u003c/sup\u003e day old. (Mean \u0026plusmn; SEM) (n=30)\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"100%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 31px;\"\u003e\n \u003cp\u003eGroup\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 19px;\"\u003e\n \u003cp\u003eBone Marrow\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 13px;\"\u003e\n \u003cp\u003eLiver\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 11px;\"\u003e\n \u003cp\u003eKidney\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 13px;\"\u003e\n \u003cp\u003eSpleen\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 11px;\"\u003e\n \u003cp\u003eLungs\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 6px;\"\u003e\n \u003cp\u003e#\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 12px;\"\u003e\n \u003cp\u003e%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 4px;\"\u003e\n \u003cp\u003e#\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8px;\"\u003e\n \u003cp\u003e%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 4px;\"\u003e\n \u003cp\u003e#\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 7px;\"\u003e\n \u003cp\u003e%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 4px;\"\u003e\n \u003cp\u003e#\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8px;\"\u003e\n \u003cp\u003e%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 4px;\"\u003e\n \u003cp\u003e#\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 6px;\"\u003e\n \u003cp\u003e%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 31px;\"\u003e\n \u003cp\u003e-ve Control\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 6px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 12px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 4px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 4px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 7px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 4px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 4px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 6px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 31px;\"\u003e\n \u003cp\u003e+ve Control\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 6px;\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 12px;\"\u003e\n \u003cp\u003e80\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 4px;\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8px;\"\u003e\n \u003cp\u003e100\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 4px;\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 7px;\"\u003e\n \u003cp\u003e80\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 4px;\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8px;\"\u003e\n \u003cp\u003e100\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 4px;\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 6px;\"\u003e\n \u003cp\u003e60\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 31px;\"\u003e\n \u003cp\u003eLevofloxacin\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 6px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 12px;\"\u003e\n \u003cp\u003e20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 4px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8px;\"\u003e\n \u003cp\u003e20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 4px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 7px;\"\u003e\n \u003cp\u003e20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 4px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8px;\"\u003e\n \u003cp\u003e20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 4px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 6px;\"\u003e\n \u003cp\u003e20\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 31px;\"\u003e\n \u003cp\u003eEnrofloxacin\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 6px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 12px;\"\u003e\n \u003cp\u003e40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 4px;\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8px;\"\u003e\n \u003cp\u003e60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 4px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 7px;\"\u003e\n \u003cp\u003e40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 4px;\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8px;\"\u003e\n \u003cp\u003e60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 4px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 6px;\"\u003e\n \u003cp\u003e40\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 31px;\"\u003e\n \u003cp\u003eEnrofloxacin+ Colistin\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 6px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 12px;\"\u003e\n \u003cp\u003e40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 4px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8px;\"\u003e\n \u003cp\u003e40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 4px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 7px;\"\u003e\n \u003cp\u003e40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 4px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 8px;\"\u003e\n \u003cp\u003e40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 4px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 6px;\"\u003e\n \u003cp\u003e20\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e(#) = number of positive samples out of five. (%) = percentage of positive samples. The samples were collected post-treatment on the 21\u003csup\u003est\u003c/sup\u003e day of age. \u003cstrong\u003e\u003cbr\u003e\u003c/strong\u003e\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThis study investigated the comparative effects of Levofloxacin and Enrofloxacin in broilers infected with avian pathogenic Escherichia coli (APEC), with particular focus on growth performance, mortality rate, health parameters, and biochemical and oxidative stress markers. The findings indicate that Levofloxacin offers several advantages over Enrofloxacin, suggesting its superiority as an antimicrobial agent in managing colibacillosis in broilers.\u003c/p\u003e \u003cp\u003eThe in vitro susceptibility profile underscores the superior antibacterial potency of levofloxacin over enrofloxacin against biofilm forming E.coli isolates. Our findings show that levofloxacin achieved a sensitivity rate of 43.75% among strong biofilm producers, nearly double that of enrofloxacin (18.75%). This aligns with the significantly larger inhibition zones observed for levofloxacin (26 mm vs. 13 mm for enrofloxacin), reinforcing its enhanced in vitro efficacy. The higher resistance observed against enrofloxacin (50.00%) compared to levofloxacin (37.50%) may reflect increasing resistance to second generation fluoroquinolones in poultry environments, as noted in previous surveillance studies [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. These results support the pharmacological rationale for considering levofloxacin as a more effective alternative for managing colibacillosis, particularly in infections involving biofilm forming strains [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. Levofloxacin reduced viable biofilm-embedded E. coli by 85%, Enrofloxacin achieved only a 45% reduction, and Enrofloxacin\u0026thinsp;+\u0026thinsp;Colistin achieved a 65% reduction. These results are consistent with the work conducted by Ishida et al. [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e], which indicates the important function of levofloxacin in treating infectious diseases associated with biofilm-forming bacteria.\u003c/p\u003e \u003cp\u003eLevofloxacin-treated chickens showed significantly higher body weight gain (BWG) and a more efficient feed conversion ratio (FCR) than those treated with Enrofloxacin. These findings align with prior research that associates Levofloxacin with improved nutrient utilization and enhanced growth outcomes. These effects may be attributed to Levofloxacin\u0026rsquo;s pharmacokinetic properties, including improved tissue penetration and a longer half-life, which enhance the bactericidal effect and reduce the persistence of infection [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. The mortality rate was notably lower in the Levofloxacin group than in the Enrofloxacin groups, reinforcing the antibiotic\u0026rsquo;s effectiveness in managing colibacillosis, especially as disease severity escalated. This reduced mortality can be attributed to Levofloxacin\u0026rsquo;s more extensive antibacterial activity, providing effective coverage against Gram-negative bacteria like APEC, a critical feature in high-density poultry farming environments where bacterial resistance and infection spread are pressing concerns [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eHematological examination revealed that broilers treated with levofloxacin maintained relatively stable RBC counts, Hb concentration, and PCV throughout the experimental period, with no statistically significant deviations from the negative control group. In contrast, the positive control group and enrofloxacin-treated groups showed notable elevations in total WBC counts, particularly on days 21 and 28 post-infection. The elevated WBC counts observed in the untreated infected group reflect an active systemic inflammatory and immune response triggered by APEC infection, consistent with the septicemic nature of colibacillosis. Similar leukocytosis in \u003cem\u003eE. coli\u003c/em\u003e\u0026ndash;infected broilers has been previously reported and is considered a hallmark of acute bacterial infection and endotoxemia [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e].The persistence of relatively higher WBC counts in the enrofloxacin and enrofloxacin\u0026ndash;colistin groups suggests a slower or less complete resolution of infection-associated inflammation compared with levofloxacin. The comparatively normalized WBC counts observed in the levofloxacin-treated group indicate more effective bacterial clearance and reduced systemic inflammatory stimulation. This finding agrees with Varia et al. [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e], who reported that third-generation fluoroquinolones exert a more balanced immunological impact in poultry, limiting excessive leukocytic responses while maintaining host defense. RBC, Hb, and PCV values did not differ significantly among treated groups, suggesting that neither levofloxacin nor enrofloxacin induced anemia or hematopoietic suppression at the administered therapeutic doses. However, Mostafa [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e] reported mild reductions in RBC and Hb on days 5 and 7 post-treatment by levofloxacin, and these values normalized by day 9. This underscores the necessity of strictly following the levofloxacin dosage to prevent alterations in hematological parameters.\u003c/p\u003e \u003cp\u003eLevofloxacin-treated birds exhibited significantly lower ALT and AST activities compared to the enrofloxacin-treated groups across all sampling periods. These findings indicate reduced hepatocellular stress and improved hepatic integrity in levofloxacin-treated broilers. While enrofloxacin is effective against E. coli, it may exert a greater hepatic metabolic burden or slower resolution of infection-related liver damage. These results align with the observations made by Varia et al. [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e], which indicated that birds treated with levofloxacin exhibited normal levels of ALT and AST activities. Serum uric acid and creatinine levels were significantly elevated in enrofloxacin-treated groups compared with levofloxacin-treated birds and controls. Elevated uric acid and creatinine concentrations are indicative of renal stress or impaired glomerular filtration, which may result from drug-induced nephrotoxicity or systemic inflammatory damage [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. The relatively stable renal biomarkers observed in the levofloxacin group suggest better renal tolerance and reduced nephrotoxic risk. This result is consistent with the conclusions drawn by Varia et al. [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e], which indicated that broilers treated with levofloxacin exhibited normal renal functions. Conversely, some studies have reported minimal biochemical differences between enrofloxacin and levofloxacin when administered at lower doses or for shorter durations. These discrepancies may be attributed to differences in experimental design, infection severity, dosage regimens, and duration of exposure, emphasizing the importance of context when interpreting fluoroquinolone safety data.\u003c/p\u003e \u003cp\u003eOxidative stress is a key pathological consequence of APEC infection and contributes to tissue damage and disease severity in broilers. In the present study, oxidative stress markers differed markedly among treatment groups, highlighting the influence of antimicrobial choice on redox balance during colibacillosis. Broilers in the positive control group exhibited significantly increased malondialdehyde (MDA) levels accompanied by decreased superoxide dismutase (SOD) and reduced glutathione (GSH) activities, indicating enhanced lipid peroxidation and impaired antioxidant defenses. These findings are consistent with previous reports showing that APEC infection induces excessive reactive oxygen species (ROS) production through endotoxin-mediated inflammatory responses [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. Levofloxacin treatment significantly reduced MDA concentrations and restored SOD and GSH levels toward normal values, suggesting effective mitigation of oxidative damage. This improvement likely reflects more efficient bacterial clearance and reduced inflammatory stimulation, resulting in lower ROS generation. Similar observations were reported by Al-Safi and Kafi [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e] and Mostafa [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e], who demonstrated that levofloxacin therapy was associated with improved antioxidant status in broilers affected by colibacillosis. In contrast, enrofloxacin-treated birds showed only partial normalization of oxidative stress markers, with persistently higher MDA levels and lower antioxidant enzyme activities compared with the levofloxacin group. This may be attributed to slower resolution of infection or fluoroquinolone-induced oxidative effects related to mitochondrial ROS generation, as previously described by Miao and Hu [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e] and Zhang and Li [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]. The enrofloxacin\u0026ndash;colistin combination did not confer additional antioxidant benefits and, in some cases, showed comparable or greater oxidative stress, possibly due to the known oxidative and nephrotoxic potential of colistin. Some studies have reported minimal differences between fluoroquinolones in healthy birds [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e, \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e] however, such discrepancies may be explained by the absence of infection-induced oxidative stress in those models. Under infectious challenge, the present findings indicate that levofloxacin provides superior protection against oxidative damage compared with enrofloxacin. Overall, the oxidative stress results suggest that levofloxacin not only effectively controls APEC infection but also preserves antioxidant defenses and limits lipid peroxidation, contributing to improved tissue integrity and recovery in broiler chickens.\u003c/p\u003e \u003cp\u003eOn day 21, samples from the Levofloxacin group showed a lower bacterial count than those from the Enrofloxacin groups, indicating that Levofloxacin was more effective against APEC. This finding is supported by the work of Noviello et al. [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e] which indicated that Levofloxacin achieved 99.9% reduction of E. coli after 6 hours at its MIC, highlighting its potent bactericidal effects. Alawkally and Al-Saadi [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e] demonstrated that Levofloxacin exhibited considerable sensitivity against various bacterial pathogens, including E. coli, resulting in markedly reduced bacterial survival in comparison to other fluoroquinolones. This underscores the superior efficacy of Levofloxacin against APEC when contrasted with Enrofloxacin.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThe study findings strongly suggest that Levofloxacin is more effective than Enrofloxacin in treating colibacillosis in broiler chickens. Levofloxacin treatment resulted in greater body weight gain, improved feed conversion, lower mortality rates, and enhanced overall health compared to Enrofloxacin. Additionally, Levofloxacin demonstrated better biochemical stability and less oxidative stress in treated chickens, suggesting a more favorable safety profile. The enhanced microbiological efficacy of Levofloxacin further supports its role as a viable therapeutic option for managing colibacillosis, contributing to improved animal welfare and productivity.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe data sets spent and/or analyzed during this study are available from the corresponding author upon reason able request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAli M. Asy contributed to the study design and assisted in data interpretation and manuscript revision. Amany O. Selim participated in collection of samples\u0026nbsp;and isolation and identification of E. coli Penetration of the drugs in biofilm. Dalia M. Azab assisted in study the animal experiments, data collection and\u0026nbsp;Hematological parameters.\u0026nbsp;Eman A. Abozeid contributed to Growth performance parameters,\u0026nbsp;Oxidative stress parameters\u0026nbsp;and critical revision of the manuscript. Mona A. Elkholy contributed to\u0026nbsp;Biochemical parameters, statistical analysis and interpretation of results. Marionete Z. Nasif contributed to Antibacterial sensitivity testand critically reviewed the manuscript.\u0026nbsp;Gehan El-Saied assisted in data analysis and manuscript editing. All authors reviewed and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research received no external funding.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eKim, Y. B. et al. Molecular characterization of avian pathogenic \u003cem\u003eEscherichia coli\u003c/em\u003e from broiler chickens with colibacillosis. \u003cem\u003ePoult. Sci.\u003c/em\u003e \u003cb\u003e99\u003c/b\u003e, 1088\u0026ndash;1095 (2020).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRen, L. et al. Supplemental xylooligosaccharide attenuates growth retardation and intestinal damage in broiler chickens challenged by avian pathogenic \u003cem\u003eEscherichia coli\u003c/em\u003e. \u003cem\u003eAgriculture\u003c/em\u003e \u003cb\u003e14\u003c/b\u003e, 1684 (2024).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJiang, X., Yu, T., Wu, N., Meng, H. \u0026amp; Shi, L. Detection of qnr, aac(6\u0026prime;)-Ib-cr and qepA genes in \u003cem\u003eEscherichia coli\u003c/em\u003e isolated from cooked meat products in Henan, China. \u003cem\u003eInt. J. Food Microbiol.\u003c/em\u003e \u003cb\u003e187\u003c/b\u003e, 22\u0026ndash;25 (2014).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKathayat, D., Lokesh, D., Ranjit, S. \u0026amp; Rajashekara, G. 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Sci.\u003c/em\u003e \u003cb\u003e8\u003c/b\u003e, 186\u0026ndash;190. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.22271/oral.2022.v8.i3a.1572\u003c/span\u003e\u003cspan address=\"10.22271/oral.2022.v8.i3a.1572\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e (2022).\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Levofloxacin, Enrofloxacin, Escherichia coli, Antioxidant enzymes, Broilers","lastPublishedDoi":"10.21203/rs.3.rs-8790151/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8790151/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eAvian pathogenic Escherichia coli (APEC) causes severe colibacillosis in poultry. This study compared the efficacy of the third-generation fluoroquinolone levofloxacin and the second generation enrofloxacin against APEC. In vitro, 155 samples from broiler farms in Qalyubia, Egypt, yielded 43 E. coli isolates, with 16 forming strong biofilms. Antibacterial sensitivity testing revealed levofloxacin had a higher susceptibility rate (43.75%) and larger inhibition zones (26 mm) compared to enrofloxacin (18.75%, 13 mm). Levofloxacin demonstrated superior antibacterial activity compared to enrofloxacin (13 mm). In vivo, 150 broiler chicks were experimentally infected with a common APEC O2 strain and divided into negative control, positive control, levofloxacin-treated, enrofloxacin-treated, and enrofloxacin and colistin combination groups. Levofloxacin treatment resulted in significantly higher body weight gain, lower mortality (3.33% vs. 6.67%), and improved feed conversion ratio compared to enrofloxacin. It also produced better hematological and biochemical profiles, reduced oxidative stress markers (MDA, SOD, GSH), and achieved lower bacterial counts in organs posttreatment. The results conclusively demonstrate that levofloxacin is more effective than enrofloxacin in treating colibacillosis, offering enhanced performance, health outcomes, and microbiological clearance in broiler chickens.\u003c/p\u003e","manuscriptTitle":"Comparative Efficacies Of Current Second And Third Generation Fluoroquinolone Antibiotics On Systemic Escherichia Coli In Broiler Chickens In Qalyubia Farms","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-03-16 07:01:31","doi":"10.21203/rs.3.rs-8790151/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-04-20T10:02:31+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-04-13T06:54:01+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"154964616082002178257246735938430872125","date":"2026-04-01T15:45:51+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-03-27T13:10:04+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-03-26T02:32:02+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"215807533983933366045166535558129487077","date":"2026-03-25T20:14:17+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"270184598876897541045933656336723489180","date":"2026-03-12T11:44:34+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-03-12T07:36:50+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-03-12T07:33:39+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2026-02-24T09:08:33+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-02-20T16:50:14+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2026-02-20T16:45:02+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"a7624e51-94c9-4f1b-ba1c-b293fa15baf3","owner":[],"postedDate":"March 16th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":64414454,"name":"Health sciences/Diseases"},{"id":64414455,"name":"Biological sciences/Microbiology"}],"tags":[],"updatedAt":"2026-05-07T08:24:02+00:00","versionOfRecord":[],"versionCreatedAt":"2026-03-16 07:01:31","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8790151","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8790151","identity":"rs-8790151","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}