{"paper_id":"35635d08-957c-49ce-b5e1-b389fe54f0cc","body_text":"Comparison of the inoculum effect of in vitro antibacterial activity of IMR and CZA against ESBL-, KPC- and AmpC-producing Escherichia coli and Klebsiella pneumoniae | 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 Research Article Comparison of the inoculum effect of in vitro antibacterial activity of IMR and CZA against ESBL-, KPC- and AmpC-producing Escherichia coli and Klebsiella pneumoniae Xueting Wang, Luying Xiong, Yuan Wang, Kai Yang, Tingting Xiao, and 8 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3420446/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 10 Dec, 2023 Read the published version in Annals of Clinical Microbiology and Antimicrobials → Version 1 posted 7 You are reading this latest preprint version Abstract Objective To evaluate effect of inoculum size of extended-spectrum β-Lactamase (ESBL)-producing-, AmpC-producing-, and KPC-producing Escherichia coli and Klebsiella pneumoniae on the in vitro antibacterial effects of imipenem/relebactam (IMR) and ceftazidime/avibactam (CZA). Methods We compared the impact of inoculum size on IMR and CZA of eight clinical isolates and two standard isolates through antimicrobial susceptibility tests, time-kill assays and in vitro PK/PD studies. Result When inoculum size increased from 10 5 to 10 7 CFU/mL, an inoculum effect was observed for 25% (3/12) and 66.7% (8/12) of IMR and CZA, respectively; time-kill assays revealed that the concentration of CZA increased from ≥ 4×MIC to 16×MIC to reach 99.9% killing rate against K. pneumoniae ATCC-BAA 1705(KPC-2-producing) and 60700(SHV-27-producing and DHA-1-producing). While for IMR, a concentration from 1×MIC to 4×MIC killed 99.9% of the four strains. When the inoculum size increased to 10 9 CFU/mL, neither IMR nor CZA showed a detectable antibacterial effect, even at a high concentration. An in vitro PK/PD study revealed a clear bactericidal effect when IMR administered as 1.25g q6h when inoculum size increased. Conclusion An inoculum effect on CZA was observed more frequent than that on IMR. Among the β-lactamase-producing strains, the inoculum effect was most common for SHV-producing and KPC-producing strains. Imipenem/relebactam ceftazidime/avibactam inoculum effect ESBL KPC AmpC in vitro PK/PD study Figures Figure 1 Figure 2 Figure 3 Figure 4 Background Production of β-lactamases is the main reason underlying the antimicrobial resistance (AMR) of Gram-negative bacteria; in addition, the selection of β-lactams is closely related to the frequency and evolution of AMR [ 1 ]. Enterobacteriaceae producing extended-spectrum-β-lactamases (ESBL) and carbapenemases are the main source of multi-drug resistant, and even pan-drug resistant, bacteria worldwide. While the number of treatments is limited, making effective treatment a clinical challenge. Imipenem/cilastatin/relebactam (IMR) and ceftazidime/avibactam (CZA) are new β-lactam/β-lactamase inhibitor combinations (BLBLIs) approved by the FDA for the treatment of multi-drug resistant bacterial infections. CZA shows potent in vitro activity against ESBL-, KPC- and AmpC-producing Enterobacteriaceae , with sensitivity rates of 100%, 96.6% and 95.1%, respectively; IMR also shows good in vitro activity against ESBL-, AmpC-, and KPC-producing strains, with sensitivities of 100%, 95.1% and 84.5%, respectively [ 2 ]. However, the clinical efficacy may be poor even though the strains are sensitive in an in vitro antimicrobial susceptibility test. Differences in the bacterial load have an impact on the choice of drugs and the dosing regimens; in particular, some antibiotics are susceptible to an inoculum effect (defined as attenuated antibacterial activity with increased inoculum size), which has an impact on treatment of infections. The recommended standard bacterial inoculum for the microbroth method is 1–5×10 5 CFU/mL [ 3 ]; however, the bacterial load varies greatly according to the type and location of an infection. With respect to urinary tract infections (UTIs), the bacterial load is usually low, at about 10 5 –10 6 CFU/mL, while in intra-abdominal infections (IAIs) the bacterial load can be as high as 10 8 –10 9 CFU/mL, and that in meningitis can reach 10 9 CFU/mL [ 4 , 5 ]. A series of studies have examined the inoculum effect, and found that carbapenems are less affected than classical BLBLIs (such as piperacillin/tazobactam) and cephalosporins [ 6 , 7 ]. In clinical practice, carbapenems are recommended for the treatment of severe infections. Studies show that there is a difference between the clinical cure rates of CZA when used to treat complicated urinary tract infections (cUTIs) and complicated intra-abdominal infections (cIAIs) (92% vs. 80%, respectively) [ 8 ]; the cure rates of IMR are similar (97.1% vs . 96.3%, respectively) [ 9 , 10 ]. These findings may be related to the inoculum effect. However, there is no consensus about the impact of the inoculum effect on treatment efficacy. The purpose of this study was to use antimicrobial sensitivity tests, time-kill assays, and in vitro PK/PD studies to evaluate the in vitro inoculum effect of ESBL-, KPC-, and AmpC- producing E. coli and K. pneumoniae on IMR and CZA, thereby providing a reference for clinical application. Material and Methods Strains In this study, four clinical isolates of E. coli and four clinical isolates of K. pneumoniae were examined, as well as standard strains E. coli ATCC 25922, K. pneumoniae ATCC-BAA 1705 (KPC-2-producing), and 700603 (SHV-18-producing). Bacterial genomic DNA was extracted using the QIAamp DNA mini kit and subjected to whole genome sequencing to identify β-lactamase types (Table 1 ). Table 1 β-lactamase genotypes, and the effects of different inoculum sizes on the antibacterial MICs of CZA and IMR against E. coli and K. pneumoniae Isolate/ Species β-lactamase genes MIC (mg/L) in the presence of different inocula(CFU/mL) CZA IMR AVI = 4 mg/L AVI = 8 mg/L REL = 4 mg/L REL = 8 mg/L 10 5 10 7 10 9 10 5 10 7 10 9 10 5 10 7 10 9 10 5 10 7 10 9 E. coli ATCC 25922 - 0.06/4 0.25/4 ＞512/4 0.03/8 0.125/8 64/8 0.125/4 0.25/4 ＞512/4 0.007/8 0.03/8 64/8 56706* bla TEM−1 , bla AmpC 0.03/4 2/4 ＞512/4 0.015/8 0.125/8 128/8 0.06/4 0.125/4 ＞512/4 0.007/8 0.03/8 64/8 93174 bla AmpC , bla CTX−M−14 , bla OXA−10 0.25/4 1/4 ＞512/4 0.125/8 0.5/8 512/8 0.125/4 0.25/4 ＞512/4 0.03/8 0.06/8 128/8 19 − 3 bla CTX−M−14 0.03/4 0.25/4 ＞512/4 0.015/8 0.125/8 128/8 0.06/4 0.25/4 ＞512/4 0.007/8 0.03/8 64/8 1564 bla CTX−M−55 , bla CMY−42 , bla TEM−1b , bla CTX−M−14 8/4 32/4 ＞512/4 4/8 16/8 256/8 0.125/4 0.25/4 ＞512/4 0.03/8 0.03/8 128/8 K. pneumoniae 1705* bla KPC−2 0.125/4 1/4 ＞512/4 0.03/8 0.125/8 64/8 0.25/4 0.5/4 ＞512/4 0.007/8 0.03/8 16/8 700603 bla SHV−18 0.03/4 0.25/4 ＞512/4 0.015/8 0.06/8 64/8 0.03/4 0.25/4 ＞512/4 0.007/8 0.03/8 32/8 50666 bla CTX−M−14 , bla KPC−2 0.25/4 2/4 ＞512/4 0.06/8 1/8 256/8 0.5/4 2/4 ＞512/4 0.125/8 0.25/8 128/8 52582 bla DHA−1 , bla OXA−1 , bla SHV−187 128/4 256/4 ＞512/4 8/8 32/8 512/8 128/4 256/4 ＞512/4 2/8 4/8 128/8 60700* bla DHA−1 , bla SHV−27 0.25/4 2/4 ＞512/4 0.125/8 0.25/8 128/8 0.06/4 0.125/4 ＞512/4 0.03/8 0.03/8 64/8 K. pneumoniae 61089* bla KPC−2 , bla CTX−M−65 , bla SHV−11 0.125/4 2/4 ＞512/4 0.06/8 0.5/8 64/8 0.06/4 0.25/4 ＞512/4 0.007/8 0.03/8 32/8 79528 bla CTX−M−15 , bla SHV−27 , bla TEM−1b 0.25/4 4/4 ＞512/4 0.125/8 2/8 512/8 0.25/4 2/4 ＞512/4 0.03/8 1/8 256/8 Bold font/asterisked isolates were chosen to conduct the time-kill study and the PK/PD study. Abbreviations: CZA, ceftazidime/avibactam; IMR, imipenem/relebactam Antimicrobial sensitivity test In accordance with the Clinical and Laboratory Standards Institute (CLSI) standards [ 3 ], antibiotic susceptibility was determined using the broth microdilution method in Mueller-Hinton broth (Oxoid, Cambridge, UK). Three different inoculum sizes were used: 10 5 (standard inoculum), 10 7 , and 10 9 CFU/mL. Ceftazidime (CAZ, lot: J0100A; potency: 94%), avibactam (AVI, lot: M0321C; potency: 99%) and imipenem (IPM, lot: N1117A; potency: 95%) were purchased from Dalian Meilun Biotechnology Co., Ltd. Relebactam (REL, lot: 002D004; potency: 99.7%) was provided by MSD. E. coli ATCC25922 was used as a quality control strain. An inoculum effect was defined as an ≥ 8-fold increase in the MIC value upon exposure to a higher inoculum. All tests were carried out in triplicate. Time-kill assays Four strains showing the most significant inoculum effect ( K. pneumoniae ATCC-BAA 1705: KPC-2 producing; E. coli 56706: TEM-1- and AmpC- producing; K. pneumoniae 60700: SHV-27- and DHA-1-producing; K. pneumoniae 61089: KPC-2- and CTX-M-65-producing) were selected for the time-kill assays. The studies were performed using antibiotics at 1×, 4×, 16×, and 32×MIC and an initial inoculum size of 10 5 (standard inoculum), 10 7 , or 10 9 CFU/mL. Samples were plated using an automatic spiral spreading instrument (IUL, Barcelona, Spain) at regular time prior to counting viable colonies. All tests were carried out in triplicate. In vitro PK/PD studies PK parameters used The simulated human serum concentrations of CZA and IMR obtained after multiple intravenous administrations were based on PK data from previous studies (Table S2)[ 11 , 12 ]. In the present study, a one-compartment PK model of the agents was used for all experiments. In vitro PK/PD simulation model and measurement of antibacterial activity The study was conducted using the in vitro PK Auto Simulation System 400 (PASS-400; Dainippon Seiki, Kyoto, Japan). The bacterial suspension was injected into 100 mL of broth medium to achieve a starting inoculum of 10 5 , 10 7 , or 10 9 CFU/mL. At predetermined time points (0, 2, 4, 6, 8, 10, 14, 18, and 24 h), 1.5 mL of the test strain was collected and plated using an automatic spiral spreading instrument prior to counting colonies. The limit of clone detection was 30 CFU/mL. Each experiment was performed in triplicate to assure reproducibility. The PD parameters, including Maximum Kill Down (MKD; the difference between the minimum bacterial count and the initial count during the experiment), the difference in bacterial counts between 0 and 24 h (∆log N24), and the bacterial growth recovery time (RT; the time from first exposure to the antibiotic until the moment when the bacterial count again reached its initial level) were analysed by PASS 400 Analyse Bactericidal Activity software. The area between the control growth curve and bactericidal curves (IE) was calculated by the trapezoidal rule using GraphPad Prism 9; these data were used as the integral parameters for evaluating antimicrobial effects. Data were analysed using one-way analysis of variance, and P < 0.05 was considered statistically significant. Results Antimicrobial sensitivity test When the inoculum size increased from 10 5 to 10 7 CFU/mL, the MIC values for CZA against all strains increased by 2- to 64-fold (from 0.03–128/4 mg/L to 0.25–256/4 mg/L), and the MIC values for IMR MIC increased by 1–8-fold (0.03–128/4 mg/L to 0.125–256/4 mg/L). An inoculum effect on CZA and IMR was observed for 66.7% (8/12) and 16.7% (2/12) of isolates, respectively. The most common (by genotype) were SHV and KPC strains. When the inoculum size was 10 9 CFU/mL, the MIC value for CZA and IMR against all strains was＞512/4 mg/L. When the concentration of AVI and REL was increased from 4 to 8 mg/L, the inoculum effect of CZA decreased from 66.7% (8/12) to 33.3% (4/12), and that of IMR decreased from 25% (3/12) to 8.3% (1/12) (Table 1 ). Time-kill assays In the presence of the standard inoculum (10 5 CFU/mL), IMR at 1× MIC killed 99.9% of K. pneumoniae ATCC-BAA 1705(KPC-2-producing) and E. coli 56706 (TEM-1- and AmpC-producing) after 8 h, and 99.9% of K. pneumoniae 61089 (CTX-M-65-and KPC-2-producing) after 12 h; these effects were maintained for over 24 h. By contrast, CZA at 1× MIC led to a < 1log 10 reduction the CFU/mL of K. pneumoniae 60700 (SHV-27- and DHA-1-producing), but it was unable to match the 99.9% killing effect of IMR. CZA at 4× MIC killed 99.9% of K. pneumoniae ATCC-BAA 1705 and 61089 at 10 5 CFU/mL after 6 h, and 99.9% of K. pneumoniae 60700 after 8 h; this effect was maintained for over 24 h. When the inoculum size was increased to 10 7 CFU/mL, CZA at 16× MIC killed 99.9% of K. pneumoniae ATCC-BAA 1705 and 60700 after 24 h and 12 h, respectively; however, it had little effect on E. coli 56706 and K. pneumoniae 61089. IMR at 4× MIC killed 99.9% of the four strains after 6 or 8 h, and maintained this for over 24 h. When the inoculum size rose to 10 9 CFU/mL, CZA and IMR at high concentrations (32× MIC) still showed no bactericidal effect against four tested strains (Fig. 1 ). In vitro PK/PD study At an inoculum size of 10 5 CFU/mL, four dosing regimens (CZA 2.5g q8h; CZA 1.25g q8h; IMR 1.25g q6h; and IMR 625mg q6h) showed potent bactericidal effects. CZA 2.5g q8h and IMR 1.25g q6h killed 99.9% of four strains ( E. coli 56706, K. pneumoniae ATCC-BAA 1705, 61089 and 60700) after 24 h. The killing effects against E. coli 56706 (TEM-1- and AmpC-producing), K. pneumoniae 61089 (CTX-M-65- and KPC-2-producing), and K. pneumoniae 60700 (SHV-27- and DHA-1-producing) were maintained for 24 h; however, bacterial growth resumed after 24 in the presence of CZA 1.25g q8h. When the inoculum size increased to 10 7 or 10 9 CFU/mL, all bacteria recovered after 24 h of exposure to CZA and IMR, although it is noteworthy that regrowth after exposure to CZA was more obvious than that after exposure to IMR (Fig. 2 ). As the inoculum size increased from 10 5 to 10 7 and 10 9 CFU/mL, an obvious bactericidal effect was noted when IMR was administered at 1.25g q6h. The difference in IE was not significant for any of the inocula (66.79–75.18, 65.77–73.7 and 66.33–76.1 lgCFU/mL∙h, respectively (P＞0.05)). When CZA was administered as 2.5g q8h, the IE for K. pneumoniae ATCC-BAA 1705 was 63.26, 50.24, and 49.99 lgCFU/mL∙h (10 5 vs. 10 7 CFU/mL [P = 0.007]; 10 7 vs. 10 9 CFU/mL [P＞0.05]; and 10 5 vs. 10 9 CFU/mL [P = 0.006]); that for E.coli 56706 was 75.42, 67.47 and 63.47 lgCFU/mL∙h (10 5 vs. 10 7 CFU/mL [P = 0.008]; 10 7 vs. 10 9 CFU/mL [P＞0.05]; and 10 5 vs . 10 9 CFU/mL [P = 0.004]); that for K. pneumoniae 61089 was 62.5, 75.24 and 68.14 lgCFU/ml∙h (10 5 vs. 10 7 CFU/mL [P = 0.006]; 10 7 vs . 10 9 CFU/mL [P = 0.03]; 10 5 vs . 10 9 CFU/mL [P＞0.05]); and that for K. pneumoniae 60700 was 73.83, 67.88 and 61.56 lgCFU/ml∙h, (10 5 vs. 10 7 CFU/mL [P = 0.03]; 10 7 vs. 10 9 CFU/mL [P = 0.03]; 10 5 vs. 10 9 CFU/mL [P = 0.004]). As the inoculum size increased, CZA showed an obvious inoculum effect, although the antibacterial effect of IMR was much more pronounced than that of CZA (Fig. 3 – 4 , Table S3). Discussion In recent years, the use of carbapenems to treat severe infections has been increasing worldwide. Under the pressure of antimicrobial selection, the prevalence of carbapenem-resistant bacteria has been increasing year-on-year. Polymyxin, tigecycline and other antibiotics commonly used to treat multidrug-resistant bacterial infections show systemic toxicity and have uncertain efficacy [ 13 ]; therefore, new antimicrobial drugs are needed urgently to treat carbapenem-resistant and multidrug-resistant bacterial infections. Classical BLIs such as tazobactam, clavulanic acid and sulbactam show insufficient inhibitory activity against AmpC- or KPC-producing strains. Avibactam, a novel diazabicyclooctanone compound, exhibits potent inhibitory activity against AmpC-, OXA-48- and KPC-producing strains [ 14 ], and relebactam also exhibits good activity against SBL-, AmpC- and KPC-producing strains [ 15 ]. CZA and IMR show potent antibacterial activity against carbapenem-resistant Enterobacteriaceae [ 16 , 17 ]. The mechanisms underlying the inoculum effect are quite complicated. As the inoculum size increases, the concentration of antibacterial drugs that interact with individual bacterial cells decreases [ 18 ], weakening the antibacterial effect of the drugs. Strains with a high inoculum size can reach stationary phase faster, and expression of PBPs during the stationary phase decreases; this weakens the effect of drugs targeting PBPs [ 19 ]. At the same time, when the bacterial inoculum size is high, bacterial quorum-sensing can mediate expression of proteins that reduce antimicrobial susceptibility, such as β-lactamases [ 19 ]. A previous study found that piperacillin/tazobactam induced a large amount of β-lactamase when the bacterial inoculum size was high [ 20 ]. In the present study, as the concentration of BLI AVI and REL increased from 4 mg/L to 8 mg/L, the inoculum effect on CZA decreased from 66.7% (8/12) to 33.3% (4/12), and that on IMR decreased from 25% (3/12) to 8.3% (1/12). As the inoculum size increased, it was necessary to increase the concentration of BLI to retain the antibacterial activity of CAZ and IPM. When the inoculum size was 10 9 CFU/mL, the MIC values of CZA and IMR were > 512/4 mg/L. In the time-kill assays, even high concentrations of antibiotics (32 × MIC) did not kill the bacteria. Data from the in vitro PK/PD studies showed that the conventional recommended doses of CZA 2.5g q8h and IMR1.25g q6h allowed bacterial regrowth after 2–14 h. At a high inoculum size, a large amount of β-lactamase was produced, negating the effects of AVI and REL. CAZ and IPM are hydrolysed by β-lactamases, which reduces their antibacterial effects. Non-β-lactamase-producing E. coli ATCC 25922 showed an inoculum effect when the inoculum size increased to 10 9 CFU/mL, which may suggest that β-lactamase-production is not the only factor involved. The inoculum effect may also be affected by the type of β-lactamases in β-lactamase-producing strains. In this study, the inoculum effect was greatest against KPC-producing strains and SHV-producing strains. Queenan et al. found that the inoculum effect correlates with the catalytic efficiency of β-lactamase [ 21 ], and that the catalytic rate k2/ki of AVI for KPC-2 is 1.3 ± 0.1 × 10 4 M − 1 s − 1 [ 14 ]; therefore, the high catalytic efficiency of KPC may be the reason underlying the inoculum effect of KPC-producing strains. A previous study on the inoculum effect of ESBL-producing E. coli on piperacillin/tazobactam found no difference in frequency with respect to TEM- producing, SHV- producing, and CTX-M- producing strains [ 20 ]. The present study included K. pneumoniae but not E. coli ; therefore, the type of bacteria may have an impact on the presence of an inoculum effect. An inoculum effect on cephalosporins was observed more frequent than that on carbapenems [ 18 , 19 ]. A previous study showed that the frequencies of inoculum effect on CAZ, cefepime and cefotaxime were observed for 35%, 85% and 100% of ESBL-producing E.coli , respectively, while meropenem did not show an inoculum effect [ 22 ]. Another study found that the inoculum effect might attributable to a decrease in expression of penicillin-binding protein (PBP) [ 23 ]. CAZ has a higher affinity for PBP3 and IPM mainly binds to PBP2 [ 24 ]. When the bacterial inoculum size increases, accumulated signalling molecules such as auto-inducers 2 (AI-2) and Acyl-homoserine lactones (AHLs) mediate quorum-sensing [ 25 ]. Then upregulation of β-lactamases expression and downregulation of efflux pump expression and outer membrane protein would led to the reduction of antibiotics susceptibility [ 25 ]. The difference in the target protein between CAZ and IPM may be a possible explanation of our finding that an inoculum effect on CZA was observed more frequent than that on IMR. Many studies have showed that the inoculum effect can impact clinical outcomes [ 26 , 27 ]. One study found that when the inoculum of Pseudomonas aeruginosa increased from 5 × 10 4 CFU/mL to 5 × 10 5 and 5 × 10 6 CFU/mL, the MIC of IMR remained almost unchanged [ 28 ]. Here, we found that the frequency of inoculum effect on IMR was relatively low (25%). The clinical efficacy rates of IMR for the treatment of cUTIs and cIAIs are 97.1% and 96.3%, respectively [ 9 , 10 ], with the difference being non-significant. By contrast, the clinical efficacy rates of CZA for cUTIs and cIAIs are 92% and 80%, respectively [ 8 ]. The clinical efficacy of CZA for treating infections at different sites varies greatly, which may be related to the presence of an inoculum effect. We found that the inoculum effect on CZA was 66.7%. However, a previous study suggests that the impact of inoculum size on the in vitro antibacterial activity of CZA is less than that of IMR [ 29 ]. This discordance may be due to use of MICs below or above the measurement threshold, making it difficult to analysis MICs statistically. Also, the previous study examined carbapenem-resistant Enterobacteriaceae , whereas we tested β-lactamase-producing E. coli and K. pneumoniae . Our study has some limitations. First, the experimental strains produced a variety of β-lactamases simultaneously; the actions of these β-lactamases may have affected the antibacterial efficacy of the drugs. Second, we used only conventional recommended regimens (IMR 1.25g q6h and CZA 2.5g q8h) and low-dose regimens (IMR 625mg q6h and CZA 1.25g q8h) in the in vitro PK/PD study. The efficacy of other regimens (such as high-dose and continuous dosing regimens) on severe infections needs further study. Conclusion IMR and CZA are considered reasonable options for the treatment of multidrug-resistant bacterial infections; however, the presence of an inoculum effect may lead to their failure to treat infections with a high bacterial load (e.g., endocarditis, osteomyelitis, and meningitis); in such cases, IMR may be a better choice. In addition, the presence/absence of an inoculum effect is somewhat determined by the type of β-lactamase. Therefore, the type of β-lactamase should be taken into consideration when selecting antibacterial drugs. Abbreviations AHL Acyl-homoserine lactones AI-2 auto-inducers 2 AMR antimicrobial resistance AVI avibactam BLBLIs β-lactam/β-lactamase inhibitor combinations CAZ ceftazidime cIAIs complicated intra-abdominal infections CLSI Clinical and Laboratory Standards Institute cUTIs complicated urinary tract infections CZA ceftazidime/avibactam ESBL extended-spectrum β-Lactamase IAIs intra-abdominal infections IMR imipenem/relebactam IPM imipenem MKD Maximum Kill Down PBP penicillin-binding protein PK/PD Pharmacokinetics/Pharmacodynamics REL relebactam RT recovery time UTIs urinary tract infections Declarations Ethics approval and consent to participate: Not applicable. Consent for publication: Not applicable. Availability of data and materials: Genome sequences in this study were submitted to GenBank under the accession BioProject No.PRJNA1026749 Competing interests: The authors declare that they have no competing interests. Funding: The study was funded by Merck Sharp & Dohme. 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Leveraging antimicrobial stewardship into improving rates of carbapenem-resistant Enterobacteriaceae[J].Virulence,2017, 8 (4): 383–90. https://doi.org/10.1080/21505594.2016.1188234 . Ehmann DE, Jahic H, Ross PL, et al. Kinetics of avibactam inhibition against Class A, C, and D β-lactamases[J]. J Biol Chem. 2013;288(39):27960–71. https://doi.org/10.1074/jbc.M113.485979 . Heo Y-A, Imipenem/Cilastatin/Relebactam. A Review in Gram-Negative Bacterial Infections[J].Drugs,2021, 81 (3): 377–88. https://doi.org/10.1007/s40265-021-01471-8 . Shields RK, Potoski BA, Haidar G et al. Clinical Outcomes, Drug Toxicity, and Emergence of Ceftazidime-Avibactam Resistance Among Patients Treated for Carbapenem-Resistant Enterobacteriaceae Infections[J].Clin Infect Dis,2016, 63 (12): 1615–8. https://doi.org/10.1093/cid/ciw636 . Lob SH, Hackel MA, Kazmierczak KM et al. In Vitro Activity of Imipenem-Relebactam against Gram-Negative ESKAPE Pathogens Isolated by Clinical Laboratories in the United States in 2015 (Results from the SMART Global Surveillance Program)[J].Antimicrob Agents Chemother,2017, 61 (6). https://doi.org/10.1128/AAC.02209-16 . Udekwu KI, Parrish N, Ankomah P et al. Functional relationship between bacterial cell density and the efficacy of antibiotics[J].J Antimicrob Chemother 2009, 63 (4): 745–57. https://doi.org/10.1093/jac/dkn554 . Lenhard JR, Bulman ZP. .Inoculum effect of β-lactam antibiotics[J].J Antimicrob Chemother 2019, 74 (10): 2825–43. https://doi.org/10.1093/jac/dkz226 . López-Cerero L, Picón E, Morillo C et al. Comparative assessment of inoculum effects on the antimicrobial activity of amoxycillin-clavulanate and piperacillin-tazobactam with extended-spectrum beta-lactamase-producing and extended-spectrum beta-lactamase-non-producing Escherichia coli isolates[J].Clinical Microbiology and Infection: the Official Publication of the European Society of Clinical Microbiology and Infectious Diseases,2010, 16 (2): 132–6. https://doi.org/10.1111/j.1469-0691.2009.02893.x . Queenan AM, Foleno B, Gownley C et al. Effects of inoculum and beta-lactamase activity in AmpC- and extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae clinical isolates tested by using NCCLS ESBL methodology[J].J Clin Microbiol 2004, 42 (1): 269–75. https://doi.org/10.1128/JCM.42.1.269-275.2004 . Wu N, Chen BY, Tian SF, et al. The inoculum effect of antibiotics against CTX-M-extended-spectrum β-lactamase-producing Escherichia coli[J]. Ann Clin Microbiol Antimicrob. 2014;13:45. https://doi.org/10.1186/s12941-014-0045-1 . Stevens DL, Yan S, Bryant AE. Penicillin-binding protein expression at different growth stages determines penicillin efficacy in vitro and in vivo: an explanation for the inoculum effect[J].J Infect Dis 1993, 167 (6): 1401–5. https://doi.org/10.1093/infdis/167.6.1401 . Simpson AJ, Opal SM, Angus BJ, et al. Differential antibiotic-induced endotoxin release in severe melioidosis[J]. J Infect Dis. 2000;181(3):1014–9. https://doi.org/10.1086/315306 . Mayer C, Borges A, Flament-Simon SC et al. Quorum sensing architecture network in Escherichia coli virulence and pathogenesis[J].FEMS Microbiol Rev,2023, 47 (4). https://doi.org/10.1093/femsre/fuad031 . Miller WR, Seas C, Carvajal LP et al. The Cefazolin Inoculum Effect Is Associated With Increased Mortality in Methicillin-Susceptible Bacteremia[J].Open Forum Infectious Diseases,2018, 5 (6): ofy123. https://doi.org/10.1093/ofid/ofy123 . Karslake J, Maltas J, Brumm P et al. Population Density Modulates Drug Inhibition and Gives Rise to Potential Bistability of Treatment Outcomes for Bacterial Infections[J].PLoS Computational Biology,2016, 12 (10): e1005098. https://doi.org/10.1371/journal.pcbi.1005098 . Young K, Painter RE, Raghoobar SL et al. In vitro studies evaluating the activity of imipenem in combination with relebactam against Pseudomonas aeruginosa[J].BMC Microbiol,2019, 19 (1): 150. https://doi.org/10.1186/s12866-019-1522-7 . Danjean M, Hobson CA, Gits-Muselli M et al. Evaluation of the inoculum effect of new antibiotics against carbapenem-resistant enterobacterales[J].Clinical Microbiology and Infection: the Official Publication of the European Society of Clinical Microbiology and Infectious Diseases,2022, 28 (11): 1503.e1-1503.e3. https://doi.org/10.1016/j.cmi.2022.06.018 . Additional Declarations No competing interests reported. Supplementary Files supplementarymaterials.docx Cite Share Download PDF Status: Published Journal Publication published 10 Dec, 2023 Read the published version in Annals of Clinical Microbiology and Antimicrobials → Version 1 posted Editorial decision: Revision requested 11 Nov, 2023 Reviews received at journal 30 Oct, 2023 Reviewers agreed at journal 24 Oct, 2023 Reviewers invited by journal 19 Oct, 2023 Editor assigned by journal 17 Oct, 2023 Submission checks completed at journal 12 Oct, 2023 First submitted to journal 08 Oct, 2023 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {\"props\":{\"pageProps\":{\"initialData\":{\"identity\":\"rs-3420446\",\"acceptedTermsAndConditions\":true,\"allowDirectSubmit\":false,\"archivedVersions\":[],\"articleType\":\"Research Article\",\"associatedPublications\":[],\"authors\":[{\"id\":239598120,\"identity\":\"70babae5-97f2-48f2-9f29-4e42aaf20bb0\",\"order_by\":0,\"name\":\"Xueting Wang\",\"email\":\"\",\"orcid\":\"\",\"institution\":\"the First Hospital of Zhejiang University School of 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C), \\u003c/strong\\u003e\\u003cem\\u003e\\u003cstrong\\u003eE.coli \\u003c/strong\\u003e\\u003c/em\\u003e\\u003cstrong\\u003e56706 (D to F), \\u003c/strong\\u003e\\u003cem\\u003e\\u003cstrong\\u003eK. pneumoniae\\u003c/strong\\u003e\\u003c/em\\u003e\\u003cstrong\\u003e 61089 (G to I) and \\u003c/strong\\u003e\\u003cem\\u003e\\u003cstrong\\u003eK. pneumoniae\\u003c/strong\\u003e\\u003c/em\\u003e\\u003cstrong\\u003e 60700 (J to L) exposed to CZA and IMR. \\u003c/strong\\u003eData are expressed as the mean ± SD. The left-hand panels depict an inoculum of 10\\u003csup\\u003e5\\u003c/sup\\u003e CFU/mL; the middle panels show an inoculum of 10\\u003csup\\u003e7\\u003c/sup\\u003e CFU/mL; the right-hand panels show an inoculum of 10\\u003csup\\u003e9\\u003c/sup\\u003e CFU/mL. Abbreviations: CZA, ceftazidime/avibactam; IMR, imipenem/relebactam.\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"Onlinefloatimage1.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-3420446/v1/b680907cf8ff594a2ba0fd76.png\"},{\"id\":44728883,\"identity\":\"c45a9899-33e7-40b3-8c1b-7227d0559387\",\"added_by\":\"auto\",\"created_at\":\"2023-10-16 21:08:58\",\"extension\":\"png\",\"order_by\":2,\"title\":\"Figure 2\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":105493,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003e\\u003cem\\u003e\\u003cstrong\\u003eIn vitro\\u003c/strong\\u003e\\u003c/em\\u003e\\u003cstrong\\u003e dynamic time-kill assays for ATCC-BAA 1705 (A to C), \\u003c/strong\\u003e\\u003cem\\u003e\\u003cstrong\\u003eE. coli \\u003c/strong\\u003e\\u003c/em\\u003e\\u003cstrong\\u003e56706 (D to F), \\u003c/strong\\u003e\\u003cem\\u003e\\u003cstrong\\u003eK. pneumoniae\\u003c/strong\\u003e\\u003c/em\\u003e\\u003cstrong\\u003e 61089 (G to I) and \\u003c/strong\\u003e\\u003cem\\u003e\\u003cstrong\\u003eK. pneumoniae\\u003c/strong\\u003e\\u003c/em\\u003e\\u003cstrong\\u003e 60700 (J to L). \\u003c/strong\\u003eData are expressed as the mean ± SD. The left-hand panels depict an inoculum size of 10\\u003csup\\u003e5\\u003c/sup\\u003e CFU/mL; the middle panels show an inoculum size of 10\\u003csup\\u003e7 \\u003c/sup\\u003eCFU/mL, and the right-hand panels denote an inoculum size of 10\\u003csup\\u003e9\\u003c/sup\\u003e CFU/mL.\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"Onlinefloatimage2.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-3420446/v1/39beb53ac749f7b558cc7707.png\"},{\"id\":44728698,\"identity\":\"c698b7a9-7790-4c7c-81e4-348609582d46\",\"added_by\":\"auto\",\"created_at\":\"2023-10-16 21:07:57\",\"extension\":\"png\",\"order_by\":3,\"title\":\"Figure 3\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":159495,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003e\\u003cstrong\\u003eIE of different treatment regimens at different inoculum sizes. \\u003c/strong\\u003eATCC-BAA 1705 (A), \\u003cem\\u003eE. coli \\u003c/em\\u003e56706 (B), \\u003cem\\u003eK. pneumoniae\\u003c/em\\u003e 61089 (C) and \\u003cem\\u003eK. pneumoniae\\u003c/em\\u003e 60700 (D). Data are expressed as the mean ± SD. 1–4 represent different dosing regimens: 1 = CZA 2.5g q8h; 2 = CZA 1.25g q8h; 3 = IMR 1.25g q6h; and 4 = IMR 625mg q6h.\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"3.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-3420446/v1/14f35bb7a00234eae1178292.png\"},{\"id\":44728905,\"identity\":\"a19fb29c-7338-45a5-8a5c-0014320ab178\",\"added_by\":\"auto\",\"created_at\":\"2023-10-16 21:09:08\",\"extension\":\"png\",\"order_by\":4,\"title\":\"Figure 4\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":22988,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003e\\u003cstrong\\u003eIE of different treatment regimens against four strains at the same inoculum size. \\u003c/strong\\u003eATCC-BAA 1705 (A–C), \\u003cem\\u003eE. coli \\u003c/em\\u003e56706 (D–F), \\u003cem\\u003eK. pneumoniae\\u003c/em\\u003e 61089 (G–I), and \\u003cem\\u003eK. pneumoniae\\u003c/em\\u003e 60700 (J–L). The left-hand panels depict an inoculum size of 10\\u003csup\\u003e5\\u003c/sup\\u003e CFU/mL; the middle panels show an inoculum size of 10\\u003csup\\u003e7 \\u003c/sup\\u003eCFU/mL, and the right-hand panels denote an inoculum size of 10\\u003csup\\u003e9\\u003c/sup\\u003e CFU/mL.\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"Onlinefloatimage5.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-3420446/v1/7d81f121ef9aa3223a427c19.png\"},{\"id\":47989186,\"identity\":\"920513f9-fdd9-41fc-925f-a6b0c72f8007\",\"added_by\":\"auto\",\"created_at\":\"2023-12-11 15:08:14\",\"extension\":\"pdf\",\"order_by\":0,\"title\":\"\",\"display\":\"\",\"copyAsset\":false,\"role\":\"manuscript-pdf\",\"size\":1403080,\"visible\":true,\"origin\":\"\",\"legend\":\"\",\"description\":\"\",\"filename\":\"manuscript.pdf\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-3420446/v1/7791ce90-cb8b-464c-890e-d75cf63bcf1c.pdf\"},{\"id\":44728850,\"identity\":\"f8ca0078-454a-4fc4-9c7c-8f2803f6d09d\",\"added_by\":\"auto\",\"created_at\":\"2023-10-16 21:08:47\",\"extension\":\"docx\",\"order_by\":1,\"title\":\"\",\"display\":\"\",\"copyAsset\":false,\"role\":\"supplement\",\"size\":23543,\"visible\":true,\"origin\":\"\",\"legend\":\"\",\"description\":\"\",\"filename\":\"supplementarymaterials.docx\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-3420446/v1/2bcdfb9ac5c565b25e51e9e1.docx\"}],\"financialInterests\":\"No competing interests reported.\",\"formattedTitle\":\"Comparison of the inoculum effect of in vitro antibacterial activity of IMR and CZA against ESBL-, KPC- and AmpC-producing Escherichia coli and Klebsiella pneumoniae\",\"fulltext\":[{\"header\":\"Background\",\"content\":\"\\u003cp\\u003eProduction of β-lactamases is the main reason underlying the antimicrobial resistance (AMR) of Gram-negative bacteria; in addition, the selection of β-lactams is closely related to the frequency and evolution of AMR [\\u003cspan citationid=\\\"CR1\\\" class=\\\"CitationRef\\\"\\u003e1\\u003c/span\\u003e]. \\u003cem\\u003eEnterobacteriaceae\\u003c/em\\u003e producing extended-spectrum-β-lactamases (ESBL) and carbapenemases are the main source of multi-drug resistant, and even pan-drug resistant, bacteria worldwide. While the number of treatments is limited, making effective treatment a clinical challenge.\\u003c/p\\u003e \\u003cp\\u003eImipenem/cilastatin/relebactam (IMR) and ceftazidime/avibactam (CZA) are new β-lactam/β-lactamase inhibitor combinations (BLBLIs) approved by the FDA for the treatment of multi-drug resistant bacterial infections. CZA shows potent \\u003cem\\u003ein vitro\\u003c/em\\u003e activity against ESBL-, KPC- and AmpC-producing \\u003cem\\u003eEnterobacteriaceae\\u003c/em\\u003e, with sensitivity rates of 100%, 96.6% and 95.1%, respectively; IMR also shows good \\u003cem\\u003ein vitro\\u003c/em\\u003e activity against ESBL-, AmpC-, and KPC-producing strains, with sensitivities of 100%, 95.1% and 84.5%, respectively [\\u003cspan citationid=\\\"CR2\\\" class=\\\"CitationRef\\\"\\u003e2\\u003c/span\\u003e].\\u003c/p\\u003e \\u003cp\\u003eHowever, the clinical efficacy may be poor even though the strains are sensitive in an \\u003cem\\u003ein vitro\\u003c/em\\u003e antimicrobial susceptibility test. Differences in the bacterial load have an impact on the choice of drugs and the dosing regimens; in particular, some antibiotics are susceptible to an inoculum effect (defined as attenuated antibacterial activity with increased inoculum size), which has an impact on treatment of infections. The recommended standard bacterial inoculum for the microbroth method is 1\\u0026ndash;5\\u0026times;10\\u003csup\\u003e5\\u003c/sup\\u003e CFU/mL [\\u003cspan citationid=\\\"CR3\\\" class=\\\"CitationRef\\\"\\u003e3\\u003c/span\\u003e]; however, the bacterial load varies greatly according to the type and location of an infection. With respect to urinary tract infections (UTIs), the bacterial load is usually low, at about 10\\u003csup\\u003e5\\u003c/sup\\u003e\\u0026ndash;10\\u003csup\\u003e6\\u003c/sup\\u003e CFU/mL, while in intra-abdominal infections (IAIs) the bacterial load can be as high as 10\\u003csup\\u003e8\\u003c/sup\\u003e\\u0026ndash;10\\u003csup\\u003e9\\u003c/sup\\u003e CFU/mL, and that in meningitis can reach 10\\u003csup\\u003e9\\u003c/sup\\u003e CFU/mL [\\u003cspan citationid=\\\"CR4\\\" class=\\\"CitationRef\\\"\\u003e4\\u003c/span\\u003e, \\u003cspan citationid=\\\"CR5\\\" class=\\\"CitationRef\\\"\\u003e5\\u003c/span\\u003e]. A series of studies have examined the inoculum effect, and found that carbapenems are less affected than classical BLBLIs (such as piperacillin/tazobactam) and cephalosporins [\\u003cspan citationid=\\\"CR6\\\" class=\\\"CitationRef\\\"\\u003e6\\u003c/span\\u003e, \\u003cspan citationid=\\\"CR7\\\" class=\\\"CitationRef\\\"\\u003e7\\u003c/span\\u003e]. In clinical practice, carbapenems are recommended for the treatment of severe infections. Studies show that there is a difference between the clinical cure rates of CZA when used to treat complicated urinary tract infections (cUTIs) and complicated intra-abdominal infections (cIAIs) (92% \\u003cem\\u003evs.\\u003c/em\\u003e 80%, respectively) [\\u003cspan citationid=\\\"CR8\\\" class=\\\"CitationRef\\\"\\u003e8\\u003c/span\\u003e]; the cure rates of IMR are similar (97.1% \\u003cem\\u003evs\\u003c/em\\u003e. 96.3%, respectively) [\\u003cspan citationid=\\\"CR9\\\" class=\\\"CitationRef\\\"\\u003e9\\u003c/span\\u003e, \\u003cspan citationid=\\\"CR10\\\" class=\\\"CitationRef\\\"\\u003e10\\u003c/span\\u003e]. These findings may be related to the inoculum effect. However, there is no consensus about the impact of the inoculum effect on treatment efficacy.\\u003c/p\\u003e \\u003cp\\u003eThe purpose of this study was to use antimicrobial sensitivity tests, time-kill assays, and \\u003cem\\u003ein vitro\\u003c/em\\u003e PK/PD studies to evaluate the \\u003cem\\u003ein vitro\\u003c/em\\u003e inoculum effect of ESBL-, KPC-, and AmpC- producing \\u003cem\\u003eE. coli\\u003c/em\\u003e and \\u003cem\\u003eK. pneumoniae\\u003c/em\\u003e on IMR and CZA, thereby providing a reference for clinical application.\\u003c/p\\u003e\"},{\"header\":\"Material and Methods\",\"content\":\"\\u003cdiv id=\\\"Sec3\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003eStrains\\u003c/h2\\u003e \\u003cp\\u003eIn this study, four clinical isolates of \\u003cem\\u003eE. coli\\u003c/em\\u003e and four clinical isolates of \\u003cem\\u003eK. pneumoniae\\u003c/em\\u003e were examined, as well as standard strains \\u003cem\\u003eE. coli\\u003c/em\\u003e ATCC 25922, \\u003cem\\u003eK. pneumoniae\\u003c/em\\u003e ATCC-BAA 1705 (KPC-2-producing), and 700603 (SHV-18-producing). Bacterial genomic DNA was extracted using the QIAamp DNA mini kit and subjected to whole genome sequencing to identify β-lactamase types (Table\\u0026nbsp;\\u003cspan refid=\\\"Tab1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003e).\\u003c/p\\u003e \\u003cp\\u003e \\u003cdiv class=\\\"gridtable\\\"\\u003e\\u003ctable float=\\\"Yes\\\" id=\\\"Tab1\\\" border=\\\"1\\\"\\u003e \\u003ccaption language=\\\"En\\\"\\u003e \\u003cdiv class=\\\"CaptionNumber\\\"\\u003eTable 1\\u003c/div\\u003e \\u003cdiv class=\\\"CaptionContent\\\"\\u003e \\u003cp\\u003eβ-lactamase genotypes, and the effects of different inoculum sizes on the antibacterial MICs of CZA and IMR against \\u003cem\\u003eE. coli\\u003c/em\\u003e and \\u003cem\\u003eK. pneumoniae\\u003c/em\\u003e\\u003c/p\\u003e \\u003c/div\\u003e \\u003c/caption\\u003e \\u003ccolgroup cols=\\\"22\\\"\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c1\\\" colnum=\\\"1\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c2\\\" colnum=\\\"2\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c3\\\" colnum=\\\"3\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c4\\\" colnum=\\\"4\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c5\\\" colnum=\\\"5\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c6\\\" colnum=\\\"6\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c7\\\" colnum=\\\"7\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c8\\\" colnum=\\\"8\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c9\\\" colnum=\\\"9\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c10\\\" colnum=\\\"10\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c11\\\" colnum=\\\"11\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c12\\\" colnum=\\\"12\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c13\\\" colnum=\\\"13\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c14\\\" colnum=\\\"14\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c15\\\" colnum=\\\"15\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c16\\\" colnum=\\\"16\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c17\\\" colnum=\\\"17\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c18\\\" colnum=\\\"18\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c19\\\" colnum=\\\"19\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c20\\\" colnum=\\\"20\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c21\\\" colnum=\\\"21\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c22\\\" colnum=\\\"22\\\"\\u003e\\u003c/div\\u003e \\u003cthead\\u003e \\u003ctr\\u003e \\u003cth align=\\\"left\\\" colspan=\\\"2\\\" morerows=\\\"3\\\" nameend=\\\"c2\\\" namest=\\\"c1\\\" rowspan=\\\"4\\\"\\u003e \\u003cp\\u003eIsolate/\\u003c/p\\u003e \\u003cp\\u003eSpecies\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c3\\\" morerows=\\\"3\\\" rowspan=\\\"4\\\"\\u003e \\u003cp\\u003eβ-lactamase genes\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colspan=\\\"19\\\" nameend=\\\"c22\\\" namest=\\\"c4\\\"\\u003e \\u003cp\\u003eMIC (mg/L) in the presence of different inocula(CFU/mL)\\u003c/p\\u003e \\u003c/th\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003cth align=\\\"left\\\" colspan=\\\"10\\\" nameend=\\\"c13\\\" namest=\\\"c4\\\"\\u003e \\u003cp\\u003eCZA\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colspan=\\\"9\\\" nameend=\\\"c22\\\" namest=\\\"c14\\\"\\u003e \\u003cp\\u003eIMR\\u003c/p\\u003e \\u003c/th\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003cth align=\\\"left\\\" colspan=\\\"4\\\" nameend=\\\"c7\\\" namest=\\\"c4\\\"\\u003e \\u003cp\\u003eAVI\\u0026thinsp;=\\u0026thinsp;4 mg/L\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colspan=\\\"6\\\" nameend=\\\"c13\\\" namest=\\\"c8\\\"\\u003e \\u003cp\\u003eAVI\\u0026thinsp;=\\u0026thinsp;8 mg/L\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colspan=\\\"5\\\" nameend=\\\"c18\\\" namest=\\\"c14\\\"\\u003e \\u003cp\\u003eREL\\u0026thinsp;=\\u0026thinsp;4 mg/L\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colspan=\\\"4\\\" nameend=\\\"c22\\\" namest=\\\"c19\\\"\\u003e \\u003cp\\u003eREL\\u0026thinsp;=\\u0026thinsp;8 mg/L\\u003c/p\\u003e \\u003c/th\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e10\\u003c/b\\u003e\\u003csup\\u003e\\u003cb\\u003e5\\u003c/b\\u003e\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e10\\u003c/b\\u003e\\u003csup\\u003e\\u003cb\\u003e7\\u003c/b\\u003e\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c7\\\" namest=\\\"c6\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e10\\u003c/b\\u003e\\u003csup\\u003e\\u003cb\\u003e9\\u003c/b\\u003e\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c9\\\" namest=\\\"c8\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e10\\u003c/b\\u003e\\u003csup\\u003e\\u003cb\\u003e5\\u003c/b\\u003e\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c11\\\" namest=\\\"c10\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e10\\u003c/b\\u003e\\u003csup\\u003e\\u003cb\\u003e7\\u003c/b\\u003e\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c13\\\" namest=\\\"c12\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e10\\u003c/b\\u003e\\u003csup\\u003e\\u003cb\\u003e9\\u003c/b\\u003e\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c15\\\" namest=\\\"c14\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e10\\u003c/b\\u003e\\u003csup\\u003e\\u003cb\\u003e5\\u003c/b\\u003e\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c17\\\" namest=\\\"c16\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e10\\u003c/b\\u003e\\u003csup\\u003e\\u003cb\\u003e7\\u003c/b\\u003e\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c18\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e10\\u003c/b\\u003e\\u003csup\\u003e\\u003cb\\u003e9\\u003c/b\\u003e\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c19\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e10\\u003c/b\\u003e\\u003csup\\u003e\\u003cb\\u003e5\\u003c/b\\u003e\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c20\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e10\\u003c/b\\u003e\\u003csup\\u003e\\u003cb\\u003e7\\u003c/b\\u003e\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c22\\\" namest=\\\"c21\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e10\\u003c/b\\u003e\\u003csup\\u003e\\u003cb\\u003e9\\u003c/b\\u003e\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/th\\u003e \\u003c/tr\\u003e \\u003c/thead\\u003e \\u003ctbody\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\" morerows=\\\"4\\\" rowspan=\\\"5\\\"\\u003e \\u003cp\\u003e\\u003cem\\u003eE. coli\\u003c/em\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003eATCC 25922\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e-\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e0.06/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e0.25/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c7\\\" namest=\\\"c6\\\"\\u003e \\u003cp\\u003e＞512/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c9\\\" namest=\\\"c8\\\"\\u003e \\u003cp\\u003e0.03/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c11\\\" namest=\\\"c10\\\"\\u003e \\u003cp\\u003e0.125/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c13\\\" namest=\\\"c12\\\"\\u003e \\u003cp\\u003e64/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c15\\\" namest=\\\"c14\\\"\\u003e \\u003cp\\u003e0.125/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c17\\\" namest=\\\"c16\\\"\\u003e \\u003cp\\u003e0.25/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c18\\\"\\u003e \\u003cp\\u003e＞512/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c19\\\"\\u003e \\u003cp\\u003e0.007/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c20\\\"\\u003e \\u003cp\\u003e0.03/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c22\\\" namest=\\\"c21\\\"\\u003e \\u003cp\\u003e64/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e56706*\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003ebla\\u003c/b\\u003e\\u003csub\\u003e\\u003cb\\u003eTEM\\u0026minus;1\\u003c/b\\u003e\\u003c/sub\\u003e, \\u003cb\\u003ebla\\u003c/b\\u003e\\u003csub\\u003e\\u003cb\\u003eAmpC\\u003c/b\\u003e\\u003c/sub\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e0.03/4\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e2/4\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c7\\\" namest=\\\"c6\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e＞512/4\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c9\\\" namest=\\\"c8\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e0.015/8\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c11\\\" namest=\\\"c10\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e0.125/8\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c13\\\" namest=\\\"c12\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e128/8\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c15\\\" namest=\\\"c14\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e0.06/4\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c17\\\" namest=\\\"c16\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e0.125/4\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c18\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e＞512/4\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c19\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e0.007/8\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c20\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e0.03/8\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c22\\\" namest=\\\"c21\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e64/8\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e93174\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e\\u003cem\\u003ebla\\u003c/em\\u003e\\u003csub\\u003eAmpC\\u003c/sub\\u003e, \\u003cem\\u003ebla\\u003c/em\\u003e\\u003csub\\u003eCTX\\u0026minus;M\\u0026minus;14\\u003c/sub\\u003e, \\u003cem\\u003ebla\\u003c/em\\u003e\\u003csub\\u003eOXA\\u0026minus;10\\u003c/sub\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e0.25/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e1/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c7\\\" namest=\\\"c6\\\"\\u003e \\u003cp\\u003e＞512/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c9\\\" namest=\\\"c8\\\"\\u003e \\u003cp\\u003e0.125/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c11\\\" namest=\\\"c10\\\"\\u003e \\u003cp\\u003e0.5/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c13\\\" namest=\\\"c12\\\"\\u003e \\u003cp\\u003e512/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c15\\\" namest=\\\"c14\\\"\\u003e \\u003cp\\u003e0.125/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c17\\\" namest=\\\"c16\\\"\\u003e \\u003cp\\u003e0.25/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c18\\\"\\u003e \\u003cp\\u003e＞512/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c19\\\"\\u003e \\u003cp\\u003e0.03/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c20\\\"\\u003e \\u003cp\\u003e0.06/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c22\\\" namest=\\\"c21\\\"\\u003e \\u003cp\\u003e128/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e19\\u0026thinsp;\\u0026minus;\\u0026thinsp;3\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c3\\\"\\u003e 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colspan=\\\"2\\\" nameend=\\\"c15\\\" namest=\\\"c14\\\"\\u003e \\u003cp\\u003e0.06/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c17\\\" namest=\\\"c16\\\"\\u003e \\u003cp\\u003e0.25/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c18\\\"\\u003e \\u003cp\\u003e＞512/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c19\\\"\\u003e \\u003cp\\u003e0.007/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c20\\\"\\u003e \\u003cp\\u003e0.03/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c22\\\" namest=\\\"c21\\\"\\u003e \\u003cp\\u003e64/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e1564\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e\\u003cem\\u003ebla\\u003c/em\\u003e\\u003csub\\u003eCTX\\u0026minus;M\\u0026minus;55\\u003c/sub\\u003e, \\u003cem\\u003ebla\\u003c/em\\u003e\\u003csub\\u003eCMY\\u0026minus;42\\u003c/sub\\u003e, \\u003cem\\u003ebla\\u003c/em\\u003e\\u003csub\\u003eTEM\\u0026minus;1b\\u003c/sub\\u003e, \\u003cem\\u003ebla\\u003c/em\\u003e\\u003csub\\u003eCTX\\u0026minus;M\\u0026minus;14\\u003c/sub\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e8/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e32/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c7\\\" namest=\\\"c6\\\"\\u003e \\u003cp\\u003e＞512/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c9\\\" namest=\\\"c8\\\"\\u003e \\u003cp\\u003e4/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c11\\\" namest=\\\"c10\\\"\\u003e \\u003cp\\u003e16/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c13\\\" namest=\\\"c12\\\"\\u003e \\u003cp\\u003e256/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c15\\\" namest=\\\"c14\\\"\\u003e \\u003cp\\u003e0.125/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c17\\\" namest=\\\"c16\\\"\\u003e \\u003cp\\u003e0.25/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c18\\\"\\u003e \\u003cp\\u003e＞512/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c19\\\"\\u003e \\u003cp\\u003e0.03/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c20\\\"\\u003e \\u003cp\\u003e0.03/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c22\\\" namest=\\\"c21\\\"\\u003e 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align=\\\"left\\\" colname=\\\"c18\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e＞512/4\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c19\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e0.007/8\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c20\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e0.03/8\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c22\\\" namest=\\\"c21\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e16/8\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e\\u0026nbsp;\\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e700603\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c3\\\"\\u003e 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nameend=\\\"c15\\\" namest=\\\"c14\\\"\\u003e \\u003cp\\u003e0.03/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c17\\\" namest=\\\"c16\\\"\\u003e \\u003cp\\u003e0.25/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c18\\\"\\u003e \\u003cp\\u003e＞512/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c19\\\"\\u003e \\u003cp\\u003e0.007/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c20\\\"\\u003e \\u003cp\\u003e0.03/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c22\\\" namest=\\\"c21\\\"\\u003e \\u003cp\\u003e32/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e\\u0026nbsp;\\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e50666\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e\\u003cem\\u003ebla\\u003c/em\\u003e\\u003csub\\u003eCTX\\u0026minus;M\\u0026minus;14\\u003c/sub\\u003e, \\u003cem\\u003ebla\\u003c/em\\u003e\\u003csub\\u003eKPC\\u0026minus;2\\u003c/sub\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e0.25/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e2/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c7\\\" namest=\\\"c6\\\"\\u003e \\u003cp\\u003e＞512/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c9\\\" namest=\\\"c8\\\"\\u003e \\u003cp\\u003e0.06/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c11\\\" namest=\\\"c10\\\"\\u003e \\u003cp\\u003e1/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c13\\\" namest=\\\"c12\\\"\\u003e \\u003cp\\u003e256/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c15\\\" namest=\\\"c14\\\"\\u003e \\u003cp\\u003e0.5/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c17\\\" namest=\\\"c16\\\"\\u003e \\u003cp\\u003e2/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c18\\\"\\u003e \\u003cp\\u003e＞512/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c19\\\"\\u003e \\u003cp\\u003e0.125/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c20\\\"\\u003e \\u003cp\\u003e0.25/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c22\\\" namest=\\\"c21\\\"\\u003e \\u003cp\\u003e128/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e\\u0026nbsp;\\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e52582\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e\\u003cem\\u003ebla\\u003c/em\\u003e\\u003csub\\u003eDHA\\u0026minus;1\\u003c/sub\\u003e, \\u003cem\\u003ebla\\u003c/em\\u003e\\u003csub\\u003eOXA\\u0026minus;1\\u003c/sub\\u003e, \\u003cem\\u003ebla\\u003c/em\\u003e\\u003csub\\u003eSHV\\u0026minus;187\\u003c/sub\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e128/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e256/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c7\\\" namest=\\\"c6\\\"\\u003e \\u003cp\\u003e＞512/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c9\\\" namest=\\\"c8\\\"\\u003e \\u003cp\\u003e8/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c11\\\" namest=\\\"c10\\\"\\u003e \\u003cp\\u003e32/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c13\\\" namest=\\\"c12\\\"\\u003e \\u003cp\\u003e512/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c15\\\" namest=\\\"c14\\\"\\u003e \\u003cp\\u003e128/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c17\\\" namest=\\\"c16\\\"\\u003e \\u003cp\\u003e256/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c18\\\"\\u003e \\u003cp\\u003e＞512/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c19\\\"\\u003e \\u003cp\\u003e2/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c20\\\"\\u003e \\u003cp\\u003e4/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c22\\\" namest=\\\"c21\\\"\\u003e \\u003cp\\u003e128/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e\\u0026nbsp;\\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e60700*\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003ebla\\u003c/b\\u003e\\u003csub\\u003e\\u003cb\\u003eDHA\\u0026minus;1\\u003c/b\\u003e\\u003c/sub\\u003e, \\u003cb\\u003ebla\\u003c/b\\u003e\\u003csub\\u003e\\u003cb\\u003eSHV\\u0026minus;27\\u003c/b\\u003e\\u003c/sub\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e0.25/4\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e2/4\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c7\\\" namest=\\\"c6\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e＞512/4\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c9\\\" namest=\\\"c8\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e0.125/8\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c11\\\" namest=\\\"c10\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e0.25/8\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c13\\\" namest=\\\"c12\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e128/8\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c15\\\" namest=\\\"c14\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e0.06/4\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c17\\\" namest=\\\"c16\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e0.125/4\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c18\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e＞512/4\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c19\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e0.03/8\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c20\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e0.03/8\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c22\\\" namest=\\\"c21\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e64/8\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003e\\u003cem\\u003eK. pneumoniae\\u003c/em\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e61089*\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003ebla\\u003c/b\\u003e\\u003csub\\u003e\\u003cb\\u003eKPC\\u0026minus;2\\u003c/b\\u003e\\u003c/sub\\u003e, \\u003cb\\u003ebla\\u003c/b\\u003e\\u003csub\\u003e\\u003cb\\u003eCTX\\u0026minus;M\\u0026minus;65\\u003c/b\\u003e\\u003c/sub\\u003e, \\u003cb\\u003ebla\\u003c/b\\u003e\\u003csub\\u003e\\u003cb\\u003eSHV\\u0026minus;11\\u003c/b\\u003e\\u003c/sub\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e0.125/4\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e2/4\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e＞512/4\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c8\\\" namest=\\\"c7\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e0.06/8\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c10\\\" namest=\\\"c9\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e0.5/8\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c12\\\" namest=\\\"c11\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e64/8\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c14\\\" namest=\\\"c13\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e0.06/4\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c16\\\" namest=\\\"c15\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e0.25/4\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c18\\\" namest=\\\"c17\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e＞512/4\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c19\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e0.007/8\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c21\\\" namest=\\\"c20\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e0.03/8\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c22\\\"\\u003e \\u003cp\\u003e\\u003cb\\u003e32/8\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e\\u0026nbsp;\\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e79528\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e\\u003cem\\u003ebla\\u003c/em\\u003e\\u003csub\\u003eCTX\\u0026minus;M\\u0026minus;15\\u003c/sub\\u003e, \\u003cem\\u003ebla\\u003c/em\\u003e\\u003csub\\u003eSHV\\u0026minus;27\\u003c/sub\\u003e, \\u003cem\\u003ebla\\u003c/em\\u003e\\u003csub\\u003eTEM\\u0026minus;1b\\u003c/sub\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e0.25/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e4/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003e＞512/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c8\\\" namest=\\\"c7\\\"\\u003e \\u003cp\\u003e0.125/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c10\\\" namest=\\\"c9\\\"\\u003e \\u003cp\\u003e2/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c12\\\" namest=\\\"c11\\\"\\u003e \\u003cp\\u003e512/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c14\\\" namest=\\\"c13\\\"\\u003e \\u003cp\\u003e0.25/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c16\\\" namest=\\\"c15\\\"\\u003e \\u003cp\\u003e2/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c18\\\" namest=\\\"c17\\\"\\u003e \\u003cp\\u003e＞512/4\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c19\\\"\\u003e \\u003cp\\u003e0.03/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colspan=\\\"2\\\" nameend=\\\"c21\\\" namest=\\\"c20\\\"\\u003e \\u003cp\\u003e1/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c22\\\"\\u003e \\u003cp\\u003e256/8\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003c/tbody\\u003e \\u003c/colgroup\\u003e \\u003ctfoot\\u003e \\u003ctr\\u003e\\u003ctd colspan=\\\"22\\\"\\u003eBold font/asterisked isolates were chosen to conduct the time-kill study and the PK/PD study.\\u003c/td\\u003e\\u003c/tr\\u003e \\u003c/tfoot\\u003e \\u003c/table\\u003e\\u003cp\\u003eAbbreviations: CZA, ceftazidime/avibactam; IMR, imipenem/relebactam\\u003c/p\\u003e\\u003c/div\\u003e \\u003c/p\\u003e \\u003c/div\\u003e \\u003cdiv id=\\\"Sec4\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003eAntimicrobial sensitivity test\\u003c/h2\\u003e \\u003cp\\u003eIn accordance with the Clinical and Laboratory Standards Institute (CLSI) standards [\\u003cspan citationid=\\\"CR3\\\" class=\\\"CitationRef\\\"\\u003e3\\u003c/span\\u003e], antibiotic susceptibility was determined using the broth microdilution method in Mueller-Hinton broth (Oxoid, Cambridge, UK). Three different inoculum sizes were used: 10\\u003csup\\u003e5\\u003c/sup\\u003e (standard inoculum), 10\\u003csup\\u003e7\\u003c/sup\\u003e, and 10\\u003csup\\u003e9\\u003c/sup\\u003e CFU/mL. Ceftazidime (CAZ, lot: J0100A; potency: 94%), avibactam (AVI, lot: M0321C; potency: 99%) and imipenem (IPM, lot: N1117A; potency: 95%) were purchased from Dalian Meilun Biotechnology Co., Ltd. Relebactam (REL, lot: 002D004; potency: 99.7%) was provided by MSD. \\u003cem\\u003eE. coli\\u003c/em\\u003e ATCC25922 was used as a quality control strain. An inoculum effect was defined as an \\u0026ge;\\u0026thinsp;8-fold increase in the MIC value upon exposure to a higher inoculum. All tests were carried out in triplicate.\\u003c/p\\u003e \\u003c/div\\u003e \\u003cdiv id=\\\"Sec5\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003eTime-kill assays\\u003c/h2\\u003e \\u003cp\\u003eFour strains showing the most significant inoculum effect (\\u003cem\\u003eK. pneumoniae\\u003c/em\\u003e ATCC-BAA 1705: KPC-2 producing; \\u003cem\\u003eE. coli\\u003c/em\\u003e 56706: TEM-1- and AmpC- producing; \\u003cem\\u003eK. pneumoniae\\u003c/em\\u003e 60700: SHV-27- and DHA-1-producing; \\u003cem\\u003eK. pneumoniae\\u003c/em\\u003e 61089: KPC-2- and CTX-M-65-producing) were selected for the time-kill assays. The studies were performed using antibiotics at 1\\u0026times;, 4\\u0026times;, 16\\u0026times;, and 32\\u0026times;MIC and an initial inoculum size of 10\\u003csup\\u003e5\\u003c/sup\\u003e (standard inoculum), 10\\u003csup\\u003e7\\u003c/sup\\u003e, or 10\\u003csup\\u003e9\\u003c/sup\\u003e CFU/mL. Samples were plated using an automatic spiral spreading instrument (IUL, Barcelona, Spain) at regular time prior to counting viable colonies. All tests were carried out in triplicate.\\u003c/p\\u003e \\u003cp\\u003e \\u003cb\\u003eIn vitro\\u003c/b\\u003e \\u003cb\\u003ePK/PD studies\\u003c/b\\u003e\\u003c/p\\u003e \\u003c/div\\u003e \\u003cdiv id=\\\"Sec6\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003ePK parameters used\\u003c/h2\\u003e \\u003cp\\u003eThe simulated human serum concentrations of CZA and IMR obtained after multiple intravenous administrations were based on PK data from previous studies (Table S2)[\\u003cspan citationid=\\\"CR11\\\" class=\\\"CitationRef\\\"\\u003e11\\u003c/span\\u003e, \\u003cspan citationid=\\\"CR12\\\" class=\\\"CitationRef\\\"\\u003e12\\u003c/span\\u003e]. In the present study, a one-compartment PK model of the agents was used for all experiments.\\u003c/p\\u003e \\u003c/div\\u003e\\n\\u003ch3\\u003eIn vitro PK/PD simulation model and measurement of antibacterial activity\\u003c/h3\\u003e\\n\\u003cp\\u003eThe study was conducted using the \\u003cem\\u003ein vitro\\u003c/em\\u003e PK Auto Simulation System 400 (PASS-400; Dainippon Seiki, Kyoto, Japan). The bacterial suspension was injected into 100 mL of broth medium to achieve a starting inoculum of 10\\u003csup\\u003e5\\u003c/sup\\u003e, 10\\u003csup\\u003e7\\u003c/sup\\u003e, or 10\\u003csup\\u003e9\\u003c/sup\\u003e CFU/mL. At predetermined time points (0, 2, 4, 6, 8, 10, 14, 18, and 24 h), 1.5 mL of the test strain was collected and plated using an automatic spiral spreading instrument prior to counting colonies. The limit of clone detection was 30 CFU/mL. Each experiment was performed in triplicate to assure reproducibility.\\u003c/p\\u003e \\u003cp\\u003eThe PD parameters, including Maximum Kill Down (MKD; the difference between the minimum bacterial count and the initial count during the experiment), the difference in bacterial counts between 0 and 24 h (∆log N24), and the bacterial growth recovery time (RT; the time from first exposure to the antibiotic until the moment when the bacterial count again reached its initial level) were analysed by PASS 400 Analyse Bactericidal Activity software. The area between the control growth curve and bactericidal curves (IE) was calculated by the trapezoidal rule using GraphPad Prism 9; these data were used as the integral parameters for evaluating antimicrobial effects. Data were analysed using one-way analysis of variance, and P\\u0026thinsp;\\u0026lt;\\u0026thinsp;0.05 was considered statistically significant.\\u003c/p\\u003e\"},{\"header\":\"Results\",\"content\":\"\\u003cdiv id=\\\"Sec9\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003eAntimicrobial sensitivity test\\u003c/h2\\u003e \\u003cp\\u003eWhen the inoculum size increased from 10\\u003csup\\u003e5\\u003c/sup\\u003e to 10\\u003csup\\u003e7\\u003c/sup\\u003e CFU/mL, the MIC values for CZA against all strains increased by 2- to 64-fold (from 0.03\\u0026ndash;128/4 mg/L to 0.25\\u0026ndash;256/4 mg/L), and the MIC values for IMR MIC increased by 1\\u0026ndash;8-fold (0.03\\u0026ndash;128/4 mg/L to 0.125\\u0026ndash;256/4 mg/L). An inoculum effect on CZA and IMR was observed for 66.7% (8/12) and 16.7% (2/12) of isolates, respectively. The most common (by genotype) were SHV and KPC strains. When the inoculum size was 10\\u003csup\\u003e9\\u003c/sup\\u003e CFU/mL, the MIC value for CZA and IMR against all strains was＞512/4 mg/L. When the concentration of AVI and REL was increased from 4 to 8 mg/L, the inoculum effect of CZA decreased from 66.7% (8/12) to 33.3% (4/12), and that of IMR decreased from 25% (3/12) to 8.3% (1/12) (Table\\u0026nbsp;\\u003cspan refid=\\\"Tab1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003e).\\u003c/p\\u003e \\u003c/div\\u003e \\u003cdiv id=\\\"Sec10\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003eTime-kill assays\\u003c/h2\\u003e \\u003cp\\u003eIn the presence of the standard inoculum (10\\u003csup\\u003e5\\u003c/sup\\u003e CFU/mL), IMR at 1\\u0026times; MIC killed 99.9% of \\u003cem\\u003eK. pneumoniae\\u003c/em\\u003e ATCC-BAA 1705(KPC-2-producing) and \\u003cem\\u003eE. coli\\u003c/em\\u003e 56706 (TEM-1- and AmpC-producing) after 8 h, and 99.9% of \\u003cem\\u003eK. pneumoniae\\u003c/em\\u003e 61089 (CTX-M-65-and KPC-2-producing) after 12 h; these effects were maintained for over 24 h. By contrast, CZA at 1\\u0026times; MIC led to a\\u0026thinsp;\\u0026lt;\\u0026thinsp;1log\\u003csub\\u003e10\\u003c/sub\\u003e reduction the CFU/mL of \\u003cem\\u003eK. pneumoniae\\u003c/em\\u003e 60700 (SHV-27- and DHA-1-producing), but it was unable to match the 99.9% killing effect of IMR. CZA at 4\\u0026times; MIC killed 99.9% of \\u003cem\\u003eK. pneumoniae\\u003c/em\\u003e ATCC-BAA 1705 and 61089 at 10\\u003csup\\u003e5\\u003c/sup\\u003eCFU/mL after 6 h, and 99.9% of \\u003cem\\u003eK. pneumoniae\\u003c/em\\u003e 60700 after 8 h; this effect was maintained for over 24 h. When the inoculum size was increased to 10\\u003csup\\u003e7\\u003c/sup\\u003e CFU/mL, CZA at 16\\u0026times; MIC killed 99.9% of \\u003cem\\u003eK. pneumoniae\\u003c/em\\u003e ATCC-BAA 1705 and 60700 after 24 h and 12 h, respectively; however, it had little effect on \\u003cem\\u003eE. coli\\u003c/em\\u003e 56706 and \\u003cem\\u003eK. pneumoniae\\u003c/em\\u003e 61089. IMR at 4\\u0026times; MIC killed 99.9% of the four strains after 6 or 8 h, and maintained this for over 24 h. When the inoculum size rose to 10\\u003csup\\u003e9\\u003c/sup\\u003eCFU/mL, CZA and IMR at high concentrations (32\\u0026times; MIC) still showed no bactericidal effect against four tested strains (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003e).\\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e \\u003cp\\u003e \\u003cb\\u003eIn vitro\\u003c/b\\u003e \\u003cb\\u003ePK/PD study\\u003c/b\\u003e\\u003c/p\\u003e \\u003cp\\u003eAt an inoculum size of 10\\u003csup\\u003e5\\u003c/sup\\u003e CFU/mL, four dosing regimens (CZA 2.5g q8h; CZA 1.25g q8h; IMR 1.25g q6h; and IMR 625mg q6h) showed potent bactericidal effects. CZA 2.5g q8h and IMR 1.25g q6h killed 99.9% of four strains (\\u003cem\\u003eE. coli\\u003c/em\\u003e 56706, \\u003cem\\u003eK. pneumoniae\\u003c/em\\u003e ATCC-BAA 1705, 61089 and 60700) after 24 h. The killing effects against \\u003cem\\u003eE. coli\\u003c/em\\u003e 56706 (TEM-1- and AmpC-producing), \\u003cem\\u003eK. pneumoniae\\u003c/em\\u003e 61089 (CTX-M-65- and KPC-2-producing), and \\u003cem\\u003eK. pneumoniae\\u003c/em\\u003e 60700 (SHV-27- and DHA-1-producing) were maintained for 24 h; however, bacterial growth resumed after 24 in the presence of CZA 1.25g q8h. When the inoculum size increased to 10\\u003csup\\u003e7\\u003c/sup\\u003e or 10\\u003csup\\u003e9\\u003c/sup\\u003e CFU/mL, all bacteria recovered after 24 h of exposure to CZA and IMR, although it is noteworthy that regrowth after exposure to CZA was more obvious than that after exposure to IMR (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003e).\\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e \\u003cp\\u003eAs the inoculum size increased from 10\\u003csup\\u003e5\\u003c/sup\\u003e to 10\\u003csup\\u003e7\\u003c/sup\\u003e and 10\\u003csup\\u003e9\\u003c/sup\\u003e CFU/mL, an obvious bactericidal effect was noted when IMR was administered at 1.25g q6h. The difference in IE was not significant for any of the inocula (66.79\\u0026ndash;75.18, 65.77\\u0026ndash;73.7 and 66.33\\u0026ndash;76.1 lgCFU/mL∙h, respectively (P＞0.05)). When CZA was administered as 2.5g q8h, the IE for \\u003cem\\u003eK. pneumoniae\\u003c/em\\u003e ATCC-BAA 1705 was 63.26, 50.24, and 49.99 lgCFU/mL∙h (10\\u003csup\\u003e5\\u003c/sup\\u003e \\u003cem\\u003evs.\\u003c/em\\u003e 10\\u003csup\\u003e7\\u003c/sup\\u003e CFU/mL [P\\u0026thinsp;=\\u0026thinsp;0.007]; 10\\u003csup\\u003e7\\u003c/sup\\u003e \\u003cem\\u003evs.\\u003c/em\\u003e 10\\u003csup\\u003e9\\u003c/sup\\u003e CFU/mL [P＞0.05]; and 10\\u003csup\\u003e5\\u003c/sup\\u003e \\u003cem\\u003evs.\\u003c/em\\u003e 10\\u003csup\\u003e9\\u003c/sup\\u003e CFU/mL [P\\u0026thinsp;=\\u0026thinsp;0.006]); that for \\u003cem\\u003eE.coli\\u003c/em\\u003e 56706 was 75.42, 67.47 and 63.47 lgCFU/mL∙h (10\\u003csup\\u003e5\\u003c/sup\\u003e \\u003cem\\u003evs.\\u003c/em\\u003e 10\\u003csup\\u003e7\\u003c/sup\\u003eCFU/mL [P\\u0026thinsp;=\\u0026thinsp;0.008]; 10\\u003csup\\u003e7\\u003c/sup\\u003e \\u003cem\\u003evs.\\u003c/em\\u003e 10\\u003csup\\u003e9\\u003c/sup\\u003e CFU/mL [P＞0.05]; and 10\\u003csup\\u003e5\\u003c/sup\\u003e \\u003cem\\u003evs\\u003c/em\\u003e. 10\\u003csup\\u003e9\\u003c/sup\\u003e CFU/mL [P\\u0026thinsp;=\\u0026thinsp;0.004]); that for \\u003cem\\u003eK. pneumoniae\\u003c/em\\u003e 61089 was 62.5, 75.24 and 68.14 lgCFU/ml∙h (10\\u003csup\\u003e5\\u003c/sup\\u003e \\u003cem\\u003evs.\\u003c/em\\u003e 10\\u003csup\\u003e7\\u003c/sup\\u003e CFU/mL [P\\u0026thinsp;=\\u0026thinsp;0.006]; 10\\u003csup\\u003e7\\u003c/sup\\u003e \\u003cem\\u003evs\\u003c/em\\u003e. 10\\u003csup\\u003e9\\u003c/sup\\u003e CFU/mL [P\\u0026thinsp;=\\u0026thinsp;0.03]; 10\\u003csup\\u003e5\\u003c/sup\\u003e \\u003cem\\u003evs\\u003c/em\\u003e. 10\\u003csup\\u003e9\\u003c/sup\\u003e CFU/mL [P＞0.05]); and that for \\u003cem\\u003eK. pneumoniae\\u003c/em\\u003e 60700 was 73.83, 67.88 and 61.56 lgCFU/ml∙h, (10\\u003csup\\u003e5\\u003c/sup\\u003e \\u003cem\\u003evs.\\u003c/em\\u003e 10\\u003csup\\u003e7\\u003c/sup\\u003e CFU/mL [P\\u0026thinsp;=\\u0026thinsp;0.03]; 10\\u003csup\\u003e7\\u003c/sup\\u003e \\u003cem\\u003evs.\\u003c/em\\u003e 10\\u003csup\\u003e9\\u003c/sup\\u003e CFU/mL [P\\u0026thinsp;=\\u0026thinsp;0.03]; 10\\u003csup\\u003e5\\u003c/sup\\u003e \\u003cem\\u003evs.\\u003c/em\\u003e 10\\u003csup\\u003e9\\u003c/sup\\u003e CFU/mL [P\\u0026thinsp;=\\u0026thinsp;0.004]). As the inoculum size increased, CZA showed an obvious inoculum effect, although the antibacterial effect of IMR was much more pronounced than that of CZA (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003e\\u0026ndash;\\u003cspan refid=\\\"Fig4\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003e, Table S3).\\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e \\u003c/div\\u003e\"},{\"header\":\"Discussion\",\"content\":\"\\u003cp\\u003eIn recent years, the use of carbapenems to treat severe infections has been increasing worldwide. Under the pressure of antimicrobial selection, the prevalence of carbapenem-resistant bacteria has been increasing year-on-year. Polymyxin, tigecycline and other antibiotics commonly used to treat multidrug-resistant bacterial infections show systemic toxicity and have uncertain efficacy [\\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e]; therefore, new antimicrobial drugs are needed urgently to treat carbapenem-resistant and multidrug-resistant bacterial infections. Classical BLIs such as tazobactam, clavulanic acid and sulbactam show insufficient inhibitory activity against AmpC- or KPC-producing strains. Avibactam, a novel diazabicyclooctanone compound, exhibits potent inhibitory activity against AmpC-, OXA-48- and KPC-producing strains [\\u003cspan citationid=\\\"CR14\\\" class=\\\"CitationRef\\\"\\u003e14\\u003c/span\\u003e], and relebactam also exhibits good activity against SBL-, AmpC- and KPC-producing strains [\\u003cspan citationid=\\\"CR15\\\" class=\\\"CitationRef\\\"\\u003e15\\u003c/span\\u003e]. CZA and IMR show potent antibacterial activity against carbapenem-resistant \\u003cem\\u003eEnterobacteriaceae\\u003c/em\\u003e [\\u003cspan citationid=\\\"CR16\\\" class=\\\"CitationRef\\\"\\u003e16\\u003c/span\\u003e, \\u003cspan citationid=\\\"CR17\\\" class=\\\"CitationRef\\\"\\u003e17\\u003c/span\\u003e].\\u003c/p\\u003e \\u003cp\\u003eThe mechanisms underlying the inoculum effect are quite complicated. As the inoculum size increases, the concentration of antibacterial drugs that interact with individual bacterial cells decreases [\\u003cspan citationid=\\\"CR18\\\" class=\\\"CitationRef\\\"\\u003e18\\u003c/span\\u003e], weakening the antibacterial effect of the drugs. Strains with a high inoculum size can reach stationary phase faster, and expression of PBPs during the stationary phase decreases; this weakens the effect of drugs targeting PBPs [\\u003cspan citationid=\\\"CR19\\\" class=\\\"CitationRef\\\"\\u003e19\\u003c/span\\u003e]. At the same time, when the bacterial inoculum size is high, bacterial quorum-sensing can mediate expression of proteins that reduce antimicrobial susceptibility, such as β-lactamases [\\u003cspan citationid=\\\"CR19\\\" class=\\\"CitationRef\\\"\\u003e19\\u003c/span\\u003e]. A previous study found that piperacillin/tazobactam induced a large amount of β-lactamase when the bacterial inoculum size was high [\\u003cspan citationid=\\\"CR20\\\" class=\\\"CitationRef\\\"\\u003e20\\u003c/span\\u003e]. In the present study, as the concentration of BLI AVI and REL increased from 4 mg/L to 8 mg/L, the inoculum effect on CZA decreased from 66.7% (8/12) to 33.3% (4/12), and that on IMR decreased from 25% (3/12) to 8.3% (1/12). As the inoculum size increased, it was necessary to increase the concentration of BLI to retain the antibacterial activity of CAZ and IPM. When the inoculum size was 10\\u003csup\\u003e9\\u003c/sup\\u003e CFU/mL, the MIC values of CZA and IMR were \\u0026gt;\\u0026thinsp;512/4 mg/L. In the time-kill assays, even high concentrations of antibiotics (32 \\u0026times; MIC) did not kill the bacteria. Data from the \\u003cem\\u003ein vitro\\u003c/em\\u003e PK/PD studies showed that the conventional recommended doses of CZA 2.5g q8h and IMR1.25g q6h allowed bacterial regrowth after 2\\u0026ndash;14 h. At a high inoculum size, a large amount of β-lactamase was produced, negating the effects of AVI and REL. CAZ and IPM are hydrolysed by β-lactamases, which reduces their antibacterial effects. Non-β-lactamase-producing \\u003cem\\u003eE. coli\\u003c/em\\u003e ATCC 25922 showed an inoculum effect when the inoculum size increased to 10\\u003csup\\u003e9\\u003c/sup\\u003e CFU/mL, which may suggest that β-lactamase-production is not the only factor involved.\\u003c/p\\u003e \\u003cp\\u003eThe inoculum effect may also be affected by the type of β-lactamases in β-lactamase-producing strains. In this study, the inoculum effect was greatest against KPC-producing strains and SHV-producing strains. Queenan et al. found that the inoculum effect correlates with the catalytic efficiency of β-lactamase [\\u003cspan citationid=\\\"CR21\\\" class=\\\"CitationRef\\\"\\u003e21\\u003c/span\\u003e], and that the catalytic rate k2/ki of AVI for KPC-2 is 1.3\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;0.1 \\u0026times; 10\\u003csup\\u003e4\\u003c/sup\\u003e M\\u003csup\\u003e\\u0026minus;\\u0026thinsp;1\\u003c/sup\\u003es\\u003csup\\u003e\\u0026minus;\\u0026thinsp;1\\u003c/sup\\u003e [\\u003cspan citationid=\\\"CR14\\\" class=\\\"CitationRef\\\"\\u003e14\\u003c/span\\u003e]; therefore, the high catalytic efficiency of KPC may be the reason underlying the inoculum effect of KPC-producing strains. A previous study on the inoculum effect of ESBL-producing \\u003cem\\u003eE. coli\\u003c/em\\u003e on piperacillin/tazobactam found no difference in frequency with respect to TEM- producing, SHV- producing, and CTX-M- producing strains [\\u003cspan citationid=\\\"CR20\\\" class=\\\"CitationRef\\\"\\u003e20\\u003c/span\\u003e]. The present study included \\u003cem\\u003eK. pneumoniae\\u003c/em\\u003e but not \\u003cem\\u003eE. coli\\u003c/em\\u003e; therefore, the type of bacteria may have an impact on the presence of an inoculum effect.\\u003c/p\\u003e \\u003cp\\u003eAn inoculum effect on cephalosporins was observed more frequent than that on carbapenems [\\u003cspan citationid=\\\"CR18\\\" class=\\\"CitationRef\\\"\\u003e18\\u003c/span\\u003e, \\u003cspan citationid=\\\"CR19\\\" class=\\\"CitationRef\\\"\\u003e19\\u003c/span\\u003e]. A previous study showed that the frequencies of inoculum effect on CAZ, cefepime and cefotaxime were observed for 35%, 85% and 100% of ESBL-producing \\u003cem\\u003eE.coli\\u003c/em\\u003e, respectively, while meropenem did not show an inoculum effect [\\u003cspan citationid=\\\"CR22\\\" class=\\\"CitationRef\\\"\\u003e22\\u003c/span\\u003e]. Another study found that the inoculum effect might attributable to a decrease in expression of penicillin-binding protein (PBP) [\\u003cspan citationid=\\\"CR23\\\" class=\\\"CitationRef\\\"\\u003e23\\u003c/span\\u003e]. CAZ has a higher affinity for PBP3 and IPM mainly binds to PBP2 [\\u003cspan citationid=\\\"CR24\\\" class=\\\"CitationRef\\\"\\u003e24\\u003c/span\\u003e]. When the bacterial inoculum size increases, accumulated signalling molecules such as auto-inducers 2 (AI-2) and Acyl-homoserine lactones (AHLs) mediate quorum-sensing [\\u003cspan citationid=\\\"CR25\\\" class=\\\"CitationRef\\\"\\u003e25\\u003c/span\\u003e]. Then upregulation of β-lactamases expression and downregulation of efflux pump expression and outer membrane protein would led to the reduction of antibiotics susceptibility [\\u003cspan citationid=\\\"CR25\\\" class=\\\"CitationRef\\\"\\u003e25\\u003c/span\\u003e]. The difference in the target protein between CAZ and IPM may be a possible explanation of our finding that an inoculum effect on CZA was observed more frequent than that on IMR.\\u003c/p\\u003e \\u003cp\\u003eMany studies have showed that the inoculum effect can impact clinical outcomes [\\u003cspan citationid=\\\"CR26\\\" class=\\\"CitationRef\\\"\\u003e26\\u003c/span\\u003e, \\u003cspan citationid=\\\"CR27\\\" class=\\\"CitationRef\\\"\\u003e27\\u003c/span\\u003e]. One study found that when the inoculum of \\u003cem\\u003ePseudomonas aeruginosa\\u003c/em\\u003e increased from 5 \\u0026times; 10\\u003csup\\u003e4\\u003c/sup\\u003e CFU/mL to 5 \\u0026times; 10\\u003csup\\u003e5\\u003c/sup\\u003e and 5 \\u0026times; 10\\u003csup\\u003e6\\u003c/sup\\u003e CFU/mL, the MIC of IMR remained almost unchanged [\\u003cspan citationid=\\\"CR28\\\" class=\\\"CitationRef\\\"\\u003e28\\u003c/span\\u003e]. Here, we found that the frequency of inoculum effect on IMR was relatively low (25%). The clinical efficacy rates of IMR for the treatment of cUTIs and cIAIs are 97.1% and 96.3%, respectively [\\u003cspan citationid=\\\"CR9\\\" class=\\\"CitationRef\\\"\\u003e9\\u003c/span\\u003e, \\u003cspan citationid=\\\"CR10\\\" class=\\\"CitationRef\\\"\\u003e10\\u003c/span\\u003e], with the difference being non-significant. By contrast, the clinical efficacy rates of CZA for cUTIs and cIAIs are 92% and 80%, respectively [\\u003cspan citationid=\\\"CR8\\\" class=\\\"CitationRef\\\"\\u003e8\\u003c/span\\u003e]. The clinical efficacy of CZA for treating infections at different sites varies greatly, which may be related to the presence of an inoculum effect. We found that the inoculum effect on CZA was 66.7%. However, a previous study suggests that the impact of inoculum size on the \\u003cem\\u003ein vitro\\u003c/em\\u003e antibacterial activity of CZA is less than that of IMR [\\u003cspan citationid=\\\"CR29\\\" class=\\\"CitationRef\\\"\\u003e29\\u003c/span\\u003e]. This discordance may be due to use of MICs below or above the measurement threshold, making it difficult to analysis MICs statistically. Also, the previous study examined carbapenem-resistant \\u003cem\\u003eEnterobacteriaceae\\u003c/em\\u003e, whereas we tested β-lactamase-producing \\u003cem\\u003eE. coli\\u003c/em\\u003e and \\u003cem\\u003eK. pneumoniae\\u003c/em\\u003e.\\u003c/p\\u003e \\u003cp\\u003eOur study has some limitations. First, the experimental strains produced a variety of β-lactamases simultaneously; the actions of these β-lactamases may have affected the antibacterial efficacy of the drugs. Second, we used only conventional recommended regimens (IMR 1.25g q6h and CZA 2.5g q8h) and low-dose regimens (IMR 625mg q6h and CZA 1.25g q8h) in the \\u003cem\\u003ein vitro\\u003c/em\\u003e PK/PD study. The efficacy of other regimens (such as high-dose and continuous dosing regimens) on severe infections needs further study.\\u003c/p\\u003e\"},{\"header\":\"Conclusion\",\"content\":\"\\u003cp\\u003eIMR and CZA are considered reasonable options for the treatment of multidrug-resistant bacterial infections; however, the presence of an inoculum effect may lead to their failure to treat infections with a high bacterial load (e.g., endocarditis, osteomyelitis, and meningitis); in such cases, IMR may be a better choice. In addition, the presence/absence of an inoculum effect is somewhat determined by the type of β-lactamase. Therefore, the type of β-lactamase should be taken into consideration when selecting antibacterial drugs.\\u003c/p\\u003e\"},{\"header\":\"Abbreviations\",\"content\":\"\\u003ctable border=\\\"1\\\" cellspacing=\\\"0\\\" cellpadding=\\\"0\\\"\\u003e\\n \\u003ctbody\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003eAHL\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003eAcyl-homoserine lactones\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003eAI-2\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003eauto-inducers\\u0026nbsp;2\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003eAMR\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003eantimicrobial resistance\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003eAVI\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003eavibactam\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003eBLBLIs\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003e\\u0026beta;-lactam/\\u0026beta;-lactamase inhibitor combinations\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003eCAZ\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003eceftazidime\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003ecIAIs\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003ecomplicated intra-abdominal infections\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003eCLSI\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003eClinical and Laboratory Standards Institute\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003ecUTIs\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003ecomplicated urinary tract infections\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003eCZA\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003eceftazidime/avibactam\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003eESBL\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003eextended-spectrum \\u0026beta;-Lactamase\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003eIAIs\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003eintra-abdominal infections\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003eIMR\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003eimipenem/relebactam\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003eIPM\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003eimipenem\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003eMKD\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003eMaximum Kill Down\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003ePBP\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003epenicillin-binding protein\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003ePK/PD\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003ePharmacokinetics/Pharmacodynamics\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003eREL\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003erelebactam\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003eRT\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003erecovery time\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003ctr\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003eUTIs\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003ctd width=\\\"50%\\\" valign=\\\"top\\\"\\u003e\\n \\u003cp\\u003eurinary tract infections\\u003c/p\\u003e\\n \\u003c/td\\u003e\\n \\u003c/tr\\u003e\\n \\u003c/tbody\\u003e\\n\\u003c/table\\u003e\"},{\"header\":\"Declarations\",\"content\":\"\\u003cp\\u003e\\u003cstrong\\u003eEthics approval and consent to participate:\\u0026nbsp;\\u003c/strong\\u003eNot applicable.\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eConsent for publication:\\u0026nbsp;\\u003c/strong\\u003eNot applicable.\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eAvailability of data and materials:\\u0026nbsp;\\u003c/strong\\u003eGenome sequences in this study were submitted to GenBank under the accession BioProject No.PRJNA1026749\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eCompeting interests:\\u003c/strong\\u003e The authors declare that they have no competing interests.\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eFunding:\\u003c/strong\\u003e The study was funded by\\u003cstrong\\u003e\\u0026nbsp;\\u003c/strong\\u003eMerck Sharp \\u0026amp; Dohme.\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eAuthors\\u0026apos; contributions:\\u0026nbsp;\\u003c/strong\\u003eStudy design, X.W. and Y.X.; Data collection, X.W., L.X., Y.W., K.Y., X.C., T.C. and P.L.; Data analysis X.W., T.X., Y.Z. and D.D.; writing, X.W., Y.X., P.S. and Y.C. All authors have read and agreed to the published version of the manuscript.\\u003c/p\\u003e\"},{\"header\":\"References\",\"content\":\"\\u003col\\u003e\\u003cli\\u003e\\u003cspan\\u003ePeirano G, Pitout JDD. Extended-Spectrum β-Lactamase-Producing Enterobacteriaceae: Update on Molecular Epidemiology and Treatment Options[J]. Drugs,2019, 79 (14): 1529\\u0026ndash;41. \\u003cspan class=\\\"ExternalRef\\\"\\u003e\\u003cspan class=\\\"RefSource\\\"\\u003ehttps://doi.org/10.1007/s40265-019-01180-3\\u003c/span\\u003e\\u003cspan address=\\\"10.1007/s40265-019-01180-3\\\" targettype=\\\"DOI\\\" class=\\\"RefTarget\\\"\\u003e\\u003c/span\\u003e\\u003c/span\\u003e.\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003eKuo S-C, Wang Y-C, Tan M-C et al. 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J Infect Dis. 2000;181(3):1014\\u0026ndash;9. \\u003cspan class=\\\"ExternalRef\\\"\\u003e\\u003cspan class=\\\"RefSource\\\"\\u003ehttps://doi.org/10.1086/315306\\u003c/span\\u003e\\u003cspan address=\\\"10.1086/315306\\\" targettype=\\\"DOI\\\" class=\\\"RefTarget\\\"\\u003e\\u003c/span\\u003e\\u003c/span\\u003e.\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003eMayer C, Borges A, Flament-Simon SC et al. Quorum sensing architecture network in Escherichia coli virulence and pathogenesis[J].FEMS Microbiol Rev,2023, 47 (4). \\u003cspan class=\\\"ExternalRef\\\"\\u003e\\u003cspan class=\\\"RefSource\\\"\\u003ehttps://doi.org/10.1093/femsre/fuad031\\u003c/span\\u003e\\u003cspan address=\\\"10.1093/femsre/fuad031\\\" targettype=\\\"DOI\\\" class=\\\"RefTarget\\\"\\u003e\\u003c/span\\u003e\\u003c/span\\u003e.\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003eMiller WR, Seas C, Carvajal LP et al. 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Population Density Modulates Drug Inhibition and Gives Rise to Potential Bistability of Treatment Outcomes for Bacterial Infections[J].PLoS Computational Biology,2016, 12 (10): e1005098. \\u003cspan class=\\\"ExternalRef\\\"\\u003e\\u003cspan class=\\\"RefSource\\\"\\u003ehttps://doi.org/10.1371/journal.pcbi.1005098\\u003c/span\\u003e\\u003cspan address=\\\"10.1371/journal.pcbi.1005098\\\" targettype=\\\"DOI\\\" class=\\\"RefTarget\\\"\\u003e\\u003c/span\\u003e\\u003c/span\\u003e.\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003eYoung K, Painter RE, Raghoobar SL et al. In vitro studies evaluating the activity of imipenem in combination with relebactam against Pseudomonas aeruginosa[J].BMC Microbiol,2019, 19 (1): 150. \\u003cspan class=\\\"ExternalRef\\\"\\u003e\\u003cspan class=\\\"RefSource\\\"\\u003ehttps://doi.org/10.1186/s12866-019-1522-7\\u003c/span\\u003e\\u003cspan address=\\\"10.1186/s12866-019-1522-7\\\" targettype=\\\"DOI\\\" class=\\\"RefTarget\\\"\\u003e\\u003c/span\\u003e\\u003c/span\\u003e.\\u003c/span\\u003e\\u003c/li\\u003e \\u003cli\\u003e\\u003cspan\\u003eDanjean M, Hobson CA, Gits-Muselli M et al. Evaluation of the inoculum effect of new antibiotics against carbapenem-resistant enterobacterales[J].Clinical Microbiology and Infection: the Official Publication of the European Society of Clinical Microbiology and Infectious Diseases,2022, 28 (11): 1503.e1-1503.e3. \\u003cspan class=\\\"ExternalRef\\\"\\u003e\\u003cspan class=\\\"RefSource\\\"\\u003ehttps://doi.org/10.1016/j.cmi.2022.06.018\\u003c/span\\u003e\\u003cspan address=\\\"10.1016/j.cmi.2022.06.018\\\" targettype=\\\"DOI\\\" class=\\\"RefTarget\\\"\\u003e\\u003c/span\\u003e\\u003c/span\\u003e.\\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\":true,\"isAuthorSuppliedPdf\":false,\"isDeskRejected\":\"\",\"isHiddenFromSearch\":false,\"isInQc\":false,\"isInWorkflow\":false,\"isPdf\":false,\"isPdfUpToDate\":true,\"isWithdrawnOrRetracted\":false,\"journal\":{\"display\":true,\"email\":\"info@researchsquare.com\",\"identity\":\"annals-of-clinical-microbiology-and-antimicrobials\",\"isNatureJournal\":false,\"hasQc\":true,\"allowDirectSubmit\":false,\"externalIdentity\":\"cmam\",\"sideBox\":\"Learn more about [Annals of Clinical Microbiology and Antimicrobials](http://ann-clinmicrob.biomedcentral.com/)\",\"snPcode\":\"12941\",\"submissionUrl\":\"https://submission.nature.com/new-submission/12941/3\",\"title\":\"Annals of Clinical Microbiology and Antimicrobials\",\"twitterHandle\":\"@BioMedCentral\",\"acdcEnabled\":true,\"dfaEnabled\":true,\"editorialSystem\":\"em\",\"reportingPortfolio\":\"BMC/SO AJ\",\"inReviewEnabled\":true,\"inReviewRevisionsEnabled\":true},\"keywords\":\"Imipenem/relebactam, ceftazidime/avibactam, inoculum effect, ESBL, KPC, AmpC, in vitro PK/PD study\",\"lastPublishedDoi\":\"10.21203/rs.3.rs-3420446/v1\",\"lastPublishedDoiUrl\":\"https://doi.org/10.21203/rs.3.rs-3420446/v1\",\"license\":{\"name\":\"CC BY 4.0\",\"url\":\"https://creativecommons.org/licenses/by/4.0/\"},\"manuscriptAbstract\":\"\\u003ch2\\u003eObjective\\u003c/h2\\u003e \\u003cp\\u003eTo evaluate effect of inoculum size of extended-spectrum β-Lactamase (ESBL)-producing-, AmpC-producing-, and KPC-producing \\u003cem\\u003eEscherichia coli\\u003c/em\\u003e and \\u003cem\\u003eKlebsiella pneumoniae\\u003c/em\\u003e on the \\u003cem\\u003ein vitro\\u003c/em\\u003e antibacterial effects of imipenem/relebactam (IMR) and ceftazidime/avibactam (CZA).\\u003c/p\\u003e\\u003ch2\\u003eMethods\\u003c/h2\\u003e \\u003cp\\u003eWe compared the impact of inoculum size on IMR and CZA of eight clinical isolates and two standard isolates through antimicrobial susceptibility tests, time-kill assays and \\u003cem\\u003ein vitro\\u003c/em\\u003e PK/PD studies.\\u003c/p\\u003e\\u003ch2\\u003eResult\\u003c/h2\\u003e \\u003cp\\u003eWhen inoculum size increased from 10\\u003csup\\u003e5\\u003c/sup\\u003e to 10\\u003csup\\u003e7\\u003c/sup\\u003eCFU/mL, an inoculum effect was observed for 25% (3/12) and 66.7% (8/12) of IMR and CZA, respectively; time-kill assays revealed that the concentration of CZA increased from \\u0026ge;\\u0026thinsp;4\\u0026times;MIC to 16\\u0026times;MIC to reach 99.9% killing rate against \\u003cem\\u003eK. pneumoniae\\u003c/em\\u003e ATCC-BAA 1705(KPC-2-producing) and 60700(SHV-27-producing and DHA-1-producing). While for IMR, a concentration from 1\\u0026times;MIC to 4\\u0026times;MIC killed 99.9% of the four strains. When the inoculum size increased to 10\\u003csup\\u003e9\\u003c/sup\\u003eCFU/mL, neither IMR nor CZA showed a detectable antibacterial effect, even at a high concentration. An \\u003cem\\u003ein vitro\\u003c/em\\u003e PK/PD study revealed a clear bactericidal effect when IMR administered as 1.25g q6h when inoculum size increased.\\u003c/p\\u003e\\u003ch2\\u003eConclusion\\u003c/h2\\u003e \\u003cp\\u003eAn inoculum effect on CZA was observed more frequent than that on IMR. Among the β-lactamase-producing strains, the inoculum effect was most common for SHV-producing and KPC-producing strains.\\u003c/p\\u003e\",\"manuscriptTitle\":\"Comparison of the inoculum effect of in vitro antibacterial activity of IMR and CZA against ESBL-, KPC- and AmpC-producing Escherichia coli and Klebsiella pneumoniae\",\"msid\":\"\",\"msnumber\":\"\",\"nonDraftVersions\":[{\"code\":1,\"date\":\"2023-10-16 20:48:53\",\"doi\":\"10.21203/rs.3.rs-3420446/v1\",\"editorialEvents\":[{\"type\":\"communityComments\",\"content\":0},{\"type\":\"decision\",\"content\":\"Revision requested\",\"date\":\"2023-11-11T07:20:34+00:00\",\"index\":\"\",\"fulltext\":\"\"},{\"type\":\"editorInvitedReview\",\"content\":\"\",\"date\":\"2023-10-30T13:41:42+00:00\",\"index\":\"hide\",\"fulltext\":\"\"},{\"type\":\"reviewerAgreed\",\"content\":\"3504e824-b8d5-49e0-9474-25f2835066dd\",\"date\":\"2023-10-24T06:40:04+00:00\",\"index\":\"hide\",\"fulltext\":\"\"},{\"type\":\"reviewersInvited\",\"content\":\"\",\"date\":\"2023-10-19T07:17:24+00:00\",\"index\":\"\",\"fulltext\":\"\"},{\"type\":\"editorAssigned\",\"content\":\"\",\"date\":\"2023-10-17T08:06:41+00:00\",\"index\":\"\",\"fulltext\":\"\"},{\"type\":\"checksComplete\",\"content\":\"\",\"date\":\"2023-10-12T08:57:30+00:00\",\"index\":\"\",\"fulltext\":\"\"},{\"type\":\"submitted\",\"content\":\"Annals of Clinical Microbiology and Antimicrobials\",\"date\":\"2023-10-08T05:47:19+00:00\",\"index\":\"\",\"fulltext\":\"\"}],\"status\":\"published\",\"journal\":{\"display\":true,\"email\":\"info@researchsquare.com\",\"identity\":\"annals-of-clinical-microbiology-and-antimicrobials\",\"isNatureJournal\":false,\"hasQc\":true,\"allowDirectSubmit\":false,\"externalIdentity\":\"cmam\",\"sideBox\":\"Learn more about [Annals of Clinical Microbiology and Antimicrobials](http://ann-clinmicrob.biomedcentral.com/)\",\"snPcode\":\"12941\",\"submissionUrl\":\"https://submission.nature.com/new-submission/12941/3\",\"title\":\"Annals of Clinical Microbiology and Antimicrobials\",\"twitterHandle\":\"@BioMedCentral\",\"acdcEnabled\":true,\"dfaEnabled\":true,\"editorialSystem\":\"em\",\"reportingPortfolio\":\"BMC/SO AJ\",\"inReviewEnabled\":true,\"inReviewRevisionsEnabled\":true}}],\"origin\":\"\",\"ownerIdentity\":\"c75e5c6b-e2c9-4175-9a5b-97be6b904c72\",\"owner\":[],\"postedDate\":\"October 16th, 2023\",\"published\":true,\"recentEditorialEvents\":[],\"rejectedJournal\":[],\"revision\":\"\",\"amendment\":\"\",\"status\":\"published-in-journal\",\"subjectAreas\":[],\"tags\":[],\"updatedAt\":\"2023-12-11T15:04:08+00:00\",\"versionOfRecord\":{\"articleIdentity\":\"rs-3420446\",\"link\":\"https://doi.org/10.1186/s12941-023-00660-5\",\"journal\":{\"identity\":\"annals-of-clinical-microbiology-and-antimicrobials\",\"isVorOnly\":false,\"title\":\"Annals of Clinical Microbiology and Antimicrobials\"},\"publishedOn\":\"2023-12-10 15:01:21\",\"publishedOnDateReadable\":\"December 10th, 2023\"},\"versionCreatedAt\":\"2023-10-16 20:48:53\",\"video\":\"\",\"vorDoi\":\"10.1186/s12941-023-00660-5\",\"vorDoiUrl\":\"https://doi.org/10.1186/s12941-023-00660-5\",\"workflowStages\":[]},\"version\":\"v1\",\"identity\":\"rs-3420446\",\"journalConfig\":\"researchsquare\"},\"__N_SSP\":true},\"page\":\"/article/[identity]/[[...version]]\",\"query\":{\"redirect\":\"/article/rs-3420446\",\"identity\":\"rs-3420446\",\"version\":[\"v1\"]},\"buildId\":\"FbvkV6FR0MCFSLy54lSbu\",\"isFallback\":false,\"isExperimentalCompile\":false,\"dynamicIds\":[84888],\"gssp\":true,\"scriptLoader\":[]}","source_license":"CC-BY-4.0","license_restricted":false}