Culture Positivity and Predictors in Persistent Smear-Positive TB at Two Months

Culture Positivity and Predictors in Persistent Smear-Positive TB at Two Months | 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 Culture Positivity and Predictors in Persistent Smear-Positive TB at Two Months Junais Koleri, Faraj S Howady, Jay P N Singh, Sara Al Balushi, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6430500/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 23 Jan, 2026 Read the published version in BMC Infectious Diseases → Version 1 posted 15 You are reading this latest preprint version Abstract Introduction: In pulmonary tuberculosis (TB), smear positivity and infectivity typically decrease quickly with effective treatment, but the time required to become non-infectious varies, affecting the duration of respiratory isolation. The CDC recommends isolation until patients produce three consecutive negative sputum smears. However, it’s suggested that patients who remain smear-positive despite treatment may be shedding only non-viable bacilli, questioning the need for prolonged isolation until smear negativity is achieved. In patients remaining smear-positive after two months of therapy, we aim to evaluate this hypothesis by conducting sputum cultures to assess the viability of bacilli in their smears. Aim: This study aimed to (1) determine the proportion of culture-positive cases among pulmonary tuberculosis patients remaining smear-positive at two months of treatment and (2) identify factors predictive of culture-negative status to support earlier isolation discontinuation. Methodology: A retrospective review of electronic medical records (2016–2024) was conducted at a tertiary TB center in Qatar, targeting patients smear-positive at two months. Data included demographics, disease extent (e.g., cavitary lesions), initial and two-month acid-fast bacilli (AFB) smear counts, two-month AFB cultures, drug resistance, and comorbidities. Results: We identified 88 patients who remained smear-positive at two months of treatment. Among them, 61.4% were culture positive. Patients without cavitary lesions on the initial chest X-ray and those with two-month AFB counts <10/100 fields had a 69% negative predictive value for culture negativity. Conclusions: Over half of persistent smear-positive patients remain potentially infectious at two months. However, those without cavitary lesions and with low AFB counts could be candidates for earlier isolation discontinuation, optimizing resources and reducing patient burden. This study suggests refining isolation protocols using clinical and microbiological predictors of infectivity. Pulmonary TB smear positivity culture status respiratory isolation TB infectivity Figures Figure 1 Introduction Pulmonary tuberculosis (TB) is a major global health challenge, with airborne transmission being the primary mode of spread. Respiratory isolation is a commonly used public health measure to reduce TB transmission, but guidelines for its duration and implementation vary( 1 ). The decline in smear positivity and infectivity following the initiation of effective treatment is well-documented, yet the timeline for patients to become noninfectious varies significantly ( 2 , 3 ). The Centers for Disease Control and Prevention (CDC) recommends isolating patients until they achieve three consecutive negative sputum smears. ( 4 ). Certain patients continue to test smear-positive for an extended time despite receiving effective treatment, necessitating prolonged isolation and the challenges that come with it. In some of these cases, smear positivity may only indicate the presence of non-viable bacilli, resulting in unnecessary isolation and a strain on resources. Prolonged isolation can have significant adverse effects on patients, including psychological distress, stigmatization, and socioeconomic challenges, particularly for marginalized populations( 5 , 6 ). This study sought to determine the proportion of culture-positive cases among patients remaining smear-positive after two months of treatment and, since two-month culture results take several weeks, to identify factors predicting culture-negative status in these persistently smear-positive patients. By addressing these objectives, we hope to contribute to the development of more nuanced isolation guidelines that balance infection control with patient well-being and resource optimization. Methodology A retrospective review of electronic medical records was conducted at a tertiary-level TB management center in Qatar from 1/1/2016 to 28/2/2024. The study included pulmonary TB patients who remained sputum smear-positive beyond two months of supervised, effective treatment under respiratory isolation. Data collected included demographics, disease extent (e.g., cavitary lesions on chest X-ray, disseminated disease), initial and two-month AFB smear counts, two-month AFB cultures and time to positivity, drug resistance profiles, comorbidities (e.g., diabetes, HIV, immunosuppression), and any treatment modifications. The AFB smear microscopy and culture was performed at the National TB Reference Laboratory, HMC, Qatar, which is a CAP accredited laboratory. The heat fixed AFB smear was prepared from NALC-NaOH treated sputum specimens; followed by staining using Fluorochrome (Auramine O) method for screening and Ziehl–Neelsen (ZN) Method for confirmation of positive smears. The smears were examined under oil immersion and smear grading was performed as per WHO and CLSI guideline( 7 , 8 ). The TB culture was conducted using the automated liquid culture BACTEC MGIT 960 system (BD, USA) following the manufacturer's instructions. Positive MGIT culture tubes were further analyzed through visual inspection, smear microscopy of the culture media, and the TBcID assay (BD, USA) to identify and confirm the presence of the Mycobacterium tuberculosis complex. TB treatment for drug susceptible and drug resistant TB were according to WHO guidelines ( 9 ) The statistical analysis was designed to evaluate the relationship between persistent smear positivity and culture status at two months of treatment, as well as to identify predictors of culture negativity. Categorical variables were displayed as counts and percentages, whereas normally distributed continuous variables were summarized as means and standard deviations. Non-normally distributed variables were represented by the median, 25th, and 75th percentiles. The Shapiro-Wilk test and histograms were employed to check data for normality. The T-test was used for normally distributed variables, and the Mann-Whitney test for non-parametric variables. Categorical variables were evaluated using the Chi-square test. Univariable analysis was performed to identify the potential predictors of culture conversion in smear positive patients. To evaluate the independent effect of each factor, multivariable logistic regression was applied. A ROC curve was then plotted to determine the optimal cutoff point where sensitivity and specificity were maximized. Using this cutoff, we created a confusion matrix to assess the ability of the AFB count in smear and presence of cavity in predicting culture conversion. Based on the findings, the newly identified predictor was added to a multivariable logistic regression model, along with the presence of lung cavity in initial chest x-ray, to help refine the predictive model and enhance classification accuracy. Statistical significance was considered as a two-tailed p-value less than 0.05. Stata/SE 14.2 was used for the analysis Results The study included 88 patients with persistent smear positivity beyond two months of treatment (Table 1 ). The median age was 41.5 years, and 84% were male. Mean AFB smear count in the initial smear was 650/100 fields, in chest x-ray, cavitary lesions were found in 67% (59/88), and bilateral or multi-lobar involvement in 84% (74/88). One patient had multidrug-resistant TB (MDR-TB), nine had isoniazid mono-resistance, and six had pyrazinamide mono-resistance. HIV co-infection was rare (1/88), while 32% (28/88) had uncontrolled diabetes. Table 1 baseline characteristics Variable All cohort (N = 88) Smear positive & culture negative (N = 34) Smear positive & culture positive (N = 54) p-value Age* 41.5 (31.5–49) 43.00 (36.00–50.00) 40.50 (30.00–48.00) 0.48 Male gender 74 (84%) 30 (88.24%) 44 (81.48%) 0.4 Multi drug resistant MTB 1 ( 1.14%) 0 ( 0.00%) 1 ( 1.85%) 0.42 Pyrazinamide mono resistance 6 ( 6.82%) 2 ( 5.88%) 4 ( 7.41%) 0.78 Isoniazid mono resistance 9 ( 10.23%) 2 ( 5.88%) 7 (12.96%) 0.29 Uncontrolled Diabetes mellitus 28 (31.82%) 12 (35.29%) 16 (29.63%) 0.58 HIV positive 1 ( 1.14%) 1 ( 2.94%) 0 ( 0.00%) 0.2 Cavity in the initial chest Xray 59 (67.05%) 16 (47.06%) 43 (79.63%) 0.002 Plural effusion 4 ( 4.55%) 2 ( 5.88%) 2 ( 3.70%) 0.63 Disseminated TB 4 ( 4.55%) 1 ( 2.94%) 3 ( 5.56%) 0.57 Treatment modification due to drug induced liver injury or drug rash 10 ( 11.36%) 2 ( 5.88%) 8 (14.81%) 0.2 Number of AFB in initial smear* 650 (100–2000) 500 (100–1000) 900 (100–2500) 0.22 Days taken of initial culture positivity* 7.00 ( 6 – 9 ) 7.00 (5.00–11.00) 7.00 (6.00–9.00) 0.59 Number of AFB in 2 months smear* 10 (5–40) 5 ( 3 – 15 ) 20 (5–50) < 0.001 days taken of 2 months culture positivity* 29 (22–36) 0 29 (22–36) * Nonparametric data presented as median (IQR), and n (%) for categorical measures After two months of anti-TB treatment, 61.4% (54/88) of the cohort remained culture positive. In these patients, the mean time to culture positivity rose from 7 days at baseline to 29 days. Compared to culture-negative patients, those who remained culture-positive at two months had a significantly higher prevalence of cavitary lesions in initial chest x-ray (79% vs. 47%, p = 0.002) and higher AFB counts in two-month-smears (20/100 fields vs. 5/100 fields, p < 0.001). ROC curve analysis (Fig. 1 ) identified an AFB cutoff of 10/100 fields as predictive of two-month culture positivity (AUC: 71%, sensitivity: 63%, specificity: 74%). Patients without cavitary lesions and AFB < 10/100 fields had a negative predictive value (NPV) of 69% for two-month culture negativity (OR for culture conversion was 7.72, 95% CI: 1.90-31.36, p = 0.004). (Table 2 ) Table 2 Adjusted OR (95% Conf. interval) P value Diabetes mellitus 0.667 (0.213–2.088) 0.486 AFB > 10/100 field with presence of lung cavity 7.723(1.902–31.359) 0.004 Age 0.971(0.929–1.015) 0.189 Isoniazid monoresistance 4.332(0.692–27.138) 0.117 Pyrazinamide monoresistance 6.03(0.522–69.637) 0.15 Bilateral involvement in chest Xray 0.483(0.1471–1.584) 0.23 Drug induced hepatitis 2.116(0.332–13.507) 0.428 Days taken for initial culture positivity 0.861(0.729–1.017) 0.245 Discussion Our cohort comprised of high-burden pulmonary TB cases, as indicated by extensive radiographic changes and high initial AFB counts in sputum smears. Despite a clear treatment response evidenced by a decline in AFB count, 61.4% of persistent smear-positive patients remained culture-positive at two months, suggesting ongoing infectivity. This challenges the assumption that smear positivity during treatment solely reflects non-viable bacilli and highlights the need for a more thorough assessment of infectiousness. We found that patients without cavitary lesions and with low AFB counts were more likely to be culture-negative, suggesting they could end isolation earlier. This study contributes to understanding isolation in high-burden TB cases with persistent smear positivity, emphasizing the difficulty of balancing transmission prevention with the drawbacks of prolonged isolation in high-transmission settings. Data from diverse experimental studies suggest that infectiousness rapidly declines after effective treatment initiation, However, the exact duration of treatment required to render people with TB disease non-infectious remains uncertain( 10 – 13 ). The notion that tuberculosis infectivity decreases after two weeks of treatment, with bacilli considered non-viable, was a postulation rather than an evidence-based conclusion( 14 ). Contrary to this, a prospective cohort study in Qatar evaluated culture conversion in smear-positive pulmonary tuberculosis patients after two weeks of treatment, finding that 95.7% remained culture-positive, suggesting persistent infectivity.( 15 ) While the National Tuberculosis Controllers Association (NTCA) guidelines suggest that patients on effective anti-TB treatment for at least five days may be considered noninfectious or low-risk for transmission, regardless of sputum smear or culture results, they also recommend extended respiratory isolation in high-risk settings—such as those involving vulnerable groups like young children or immunosuppressed individuals—though the ideal isolation duration remains unclear ( 12 ). In hot and humid Middle Eastern countries, where people often spend extended periods in air-conditioned spaces with recirculated air, these factors emphasize the need for refined isolation protocols that minimize unnecessary patient burden while ensuring effective infection control. It can be argued that culture positivity confirms viable Mycobacterium tuberculosis but does not fully capture infectiousness, which also depends on cough dynamics and aerosol generation ( 16 , 17 ). Newer tests, including cough aerosol culture, have been explored to predict treatment response and guide de-isolation. Studies show a rapid decrease in culture-positive MTB in cough aerosol on effective treatment ( 18 – 22 ). However, it should be noted that recent studies showed that daily tidal breathing can generate higher bacillary count than cough per 24 hours( 23 ). Transcriptomic analysis of bacterial RNA released into the environment has been investigated as a way to study the decrease in infectiousness. Research indicates that within four days of starting treatment, bacterial mRNA levels decrease by more than 98%, indicating a swift decline in the number of viable bacilli ( 24 ). Furthermore, transcriptional profiling shows a reduction in the expression of genes linked to virulence and pathogenicity, implying that M. tuberculosis becomes less capable of initiating new infections ( 25 ). Since culture takes several weeks, a faster technique to assess bacterial viability is fluorescein diacetate vital staining. This technique identifies viable bacteria with preserved membrane integrity and has been proposed as a way to detect treatment failure before culture results are available. ( 26 , 27 ) A limitation of this study is that, although culture positivity confirms viable M. tuberculosis, it does not directly imply active transmission. Animal model studies could help assess the transmissibility of these viable bacilli, potentially refining infection control protocols and treatment efficacy assessments. Furthermore, the modest sample size of 88 patients may restrict the generalizability of these findings to the broader tuberculosis population. Conclusion In our study of high-burden TB cases with persistent smear positivity beyond two months, we found that the majority remained culture-positive, indicating the presence of viable M. tuberculosis and a potential risk of transmission. This underscores the need for continued precautions, even though the psychological adverse effects of prolonged isolation should be considered. Further research is necessary to refine our understanding of transmission risk and optimize isolation protocols. Declarations Type of study- Retrospective descriptive study Ethics approval and Consent to participate : Study was approved by the Institutional Review Board, which is the ethical committee of Medical Research Center, Hamad medical corporation, Doha, Qatar. Patient Consent Statement is not applicable as there is no patient identifiable data. Exempted from written informed consent from study participants by the Institutional Review Board. Clinical Trial number Not applicable Consent for publication: Institutional consent obtained for publication Funding: Qatar national library funding for publication. Author Contribution Junais Koleri: Study design, data collection, data analysis, manuscript writing, corresponding author.Faraj S Howady : Study design, manuscript writingJay PN Singh : Manuscript writing Sara Al Balushi : Statistical analysis, Manuscript writing Muna Al Maslamani: Study design Acknowledgement Anusha Abdulkhader ( [email protected] ) - Data retrieval. Data Availability The datasets used and analyzed during the current study are available from the corresponding author on reasonable request. References World Health Organization. WHO guidelines on tuberculosis infection prevention and control: 2019 update [Internet]. Geneva: World Health Organization. 2019 [cited 2025 Feb 25]. Available from: https://iris.who.int/handle/10665/311259 Dharmadhikari AS, Mphahlele M, Venter K, Stoltz A, Mathebula R, Masotla T, et al. Rapid impact of effective treatment on transmission of multidrug-resistant tuberculosis. Int J Tuberc Lung Dis Off J Int Union Tuberc Lung Dis. 2014;18(9):1019–25. Riley RL. Aerial dissemination of pulmonary tuberculosis. Am Rev Tuberc. 1957;76(6):931–41. Guidelines for Preventing the Transmission of Mycobacterium tuberculosis in Health-Care Facilities. 1994 [Internet]. [cited 2024 May 26]. Available from: https://www.cdc.gov/mmwr/preview/mmwrhtml/00035909.htm Cooper R, Williams M, Fennelly KP. Abandon the Acid-Fast Bacilli Smear for Patients With TB on Effective Treatment. Chest. 2023;164(1):21–3. Nathavitharana RR, Pearl A, Biewer A, Young L, Mukasa L, Delrooz N, et al. Effects of Respiratory Isolation for Tuberculosis to Reduce Community-based Transmission: A Systematic Review. Clin Infect Dis. 2025;80(1):189–98. Forbes BA, Miller MB, Banaei N, Brown-Elliott BA, Das S, Salfinger M et al. Laboratory Detection and Identification of Mycobacteria. Narvaiz de Kantor I, Kim SJ, Frieden TR, Laszlo A, Luelmo F, Norval PY et al. Laboratory services in tuberculosis control. 1998 [cited 2025 Mar 4]; Available from: https://iris.who.int/handle/10665/65942 WHO consolidated guidelines on tuberculosis. module 4: treatment: drug-resistant tuberculosis treatment [Internet]. [cited 2025 Mar 18]. Available from: https://www.who.int/publications/i/item/9789240007048 Shah M, Dansky Z, Nathavitharana R, Behm H, Brown S, Dov L et al. National Tuberculosis Coalition of America (NTCA) Guidelines for Respiratory Isolation and Restrictions to Reduce Transmission of Pulmonary Tuberculosis in Community Settings. Clin Infect Dis. 2024;ciae199. Riley RL. The contagiosity of tuberculosis. Schweiz Med Wochenschr. 1983;113(3):75–9. Escombe AR, Moore DAJ, Gilman RH, Pan W, Navincopa M, Ticona E, et al. The Infectiousness of Tuberculosis Patients Coinfected with HIV. PLOS Med. 2008;5(9):e188. Nardell Ea, Stoltz A, de Kock E, Nathavitharana R, Jensen P, Mendel C et al. Measuring the Early Impact on Transmission of New Treatment Regimens for Drug Resistant Tuberculosis. In: C27 TB TREATMENT [Internet]. American Thoracic Society; 2019 [cited 2025 Feb 23]. pp. A7387–A7387. (American Thoracic Society International Conference Abstracts). Available from: https://www.atsjournals.org/doi/ 10.1164/ajrccm-conference.2019.199.1_MeetingAbstracts.A7387 Rouillon A, Perdrizet S, Parrot R. Transmission of tubercle bacilli: The effects of chemotherapy. Tubercle. 1976;57(4):275–99. Alhowady F, Elmaki N, Ali M, Husain A, Al-Maslamani M, Alsuwaidi Z, et al. 794. Infectivity of Smear-Positive Pulmonary TB After 2 Weeks of Rifampicin-based Anti-Tuberculous Therapy. Open Forum Infect Dis. 2018;5(Suppl 1):S285–6. Calderwood CJ, Wilson JP, Fielding KL, Harris RC, Karat AS, Mansukhani R, et al. Dynamics of sputum conversion during effective tuberculosis treatment: A systematic review and meta-analysis. PLoS Med. 2021;18(4):e1003566. Al-Moamary MS, Black W, Bessuille E, Elwood RK, Vedal S. The significance of the persistent presence of acid-fast bacilli in sputum smears in pulmonary tuberculosis. Chest. 1999;116(3):726–31. Fennelly KP, Jones-López EC, Ayakaka I, Kim S, Menyha H, Kirenga B, et al. Variability of infectious aerosols produced during coughing by patients with pulmonary tuberculosis. Am J Respir Crit Care Med. 2012;186(5):450–7. Theron G, Limberis J, Venter R, Smith L, Pietersen E, Esmail A, et al. Bacterial and host determinants of cough aerosol culture-positivity in patients with drug-resistant versus drug-susceptible tuberculosis. Nat Med. 2020;26(9):1435–43. Nduba V, Njagi LN, Murithi W, Mwongera Z, Byers J, Logioia G, et al. Mycobacterium tuberculosis cough aerosol culture status associates with host characteristics and inflammatory profiles. Nat Commun. 2024;15(1):7604. Jones-López EC, Kim S, Fregona G, Marques-Rodrigues P, Hadad DJ, Molina LPD, et al. Importance of Cough and M. tuberculosis Strain Type as Risks for Increased Transmission within Households. PLoS ONE. 2014;9(7):e100984. Basu S, Andrews JR, Poolman EM, Gandhi NR, Shah NS, Moll A, et al. Prevention of nosocomial transmission of extensively drug-resistant tuberculosis in rural South African district hospitals: an epidemiological modelling study. Lancet Lond Engl. 2007;370(9597):1500–7. Dinkele R, Gessner S, McKerry A, Leonard B, Leukes J, Seldon R et al. Aerosolization of Mycobacterium tuberculosis by Tidal Breathing. Am J Respir Crit Care Med 206(2):206–16. Transcriptional Adaptation of Drug-tolerant Mycobacterium tuberculosis During Treatment of Human Tuberculosis. | The Journal of Infectious Diseases | Oxford Academic [Internet]. [cited 2025 Feb 25]. Available from: https://academic.oup.com/jid/article/212/6/990/984852 Shaikh A, Sriraman K, Vaswani S, Oswal V, Rao S, Mistry N. Early phase of effective treatment induces distinct transcriptional changes in Mycobacterium tuberculosis expelled by pulmonary tuberculosis patients. Sci Rep. 2021;11(1):17812. Kvach JT, Veras JR. A fluorescent staining procedure for determining the viability of mycobacterial cells. Int J Lepr Mycobact Dis Off Organ Int Lepr Assoc. 1982;50(2):183–92. Van Deun A, Maug AKJ, Hossain A, Gumusboga M, de Jong BC. Fluorescein diacetate vital staining allows earlier diagnosis of rifampicin-resistant tuberculosis. Int J Tuberc Lung Dis Off J Int Union Tuberc Lung Dis. 2012;16(9):1174–9. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 23 Jan, 2026 Read the published version in BMC Infectious Diseases → Version 1 posted Editorial decision: Revision requested 19 Jun, 2025 Reviews received at journal 05 Jun, 2025 Reviews received at journal 30 May, 2025 Reviewers agreed at journal 28 May, 2025 Reviews received at journal 23 May, 2025 Reviews received at journal 22 May, 2025 Reviewers agreed at journal 20 May, 2025 Reviewers agreed at journal 19 May, 2025 Reviewers agreed at journal 12 May, 2025 Reviewers agreed at journal 03 May, 2025 Reviewers agreed at journal 29 Apr, 2025 Reviewers invited by journal 29 Apr, 2025 Editor assigned by journal 15 Apr, 2025 Submission checks completed at journal 15 Apr, 2025 First submitted to journal 11 Apr, 2025 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. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-6430500","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":451639290,"identity":"4556c582-5248-4e9a-ae78-17777c0655a5","order_by":0,"name":"Junais Koleri","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA0ElEQVRIie3NsQqCUBiG4V+EXCRoOyHkLRxpKSS6FcXB6exN4QV4AYrSNQiCETT8IrQ0uDo2NSnUFtSQri1HmyLOu33DwwcgEv1gSmBJCEBmtFtqHyIFCB2ZDyCh1xGwk/4kkhHvx4W7V872rQZT55PdyMqDK2EHn6XTGFzD4xOVFioSliBLNBUKiU+ilryQuLRs0mdL1lwyCX1aABKLVizrXmwu0cjJyn0kRlI12TKmrsMlY+LklwdudVqytKo35opLPqLyQND2BRGJRKK/7w2lSUK9vzGzGQAAAABJRU5ErkJggg==","orcid":"","institution":"Hamad Medical Corporation","correspondingAuthor":true,"prefix":"","firstName":"Junais","middleName":"","lastName":"Koleri","suffix":""},{"id":451639291,"identity":"d585fd7b-0958-4b2b-9b86-3576a8a6f713","order_by":1,"name":"Faraj S Howady","email":"","orcid":"","institution":"Hamad Medical Corporation","correspondingAuthor":false,"prefix":"","firstName":"Faraj","middleName":"S","lastName":"Howady","suffix":""},{"id":451639292,"identity":"2d5a0690-b00d-481e-8556-7f33129b6070","order_by":2,"name":"Jay P N Singh","email":"","orcid":"","institution":"Hamad Medical Corporation","correspondingAuthor":false,"prefix":"","firstName":"Jay","middleName":"P N","lastName":"Singh","suffix":""},{"id":451639293,"identity":"e1149c4c-2a57-413c-b555-2ea08275c9c3","order_by":3,"name":"Sara Al Balushi","email":"","orcid":"","institution":"Hamad Medical Corporation","correspondingAuthor":false,"prefix":"","firstName":"Sara","middleName":"Al","lastName":"Balushi","suffix":""},{"id":451639294,"identity":"29f88090-ab49-43be-a69a-70417884240c","order_by":4,"name":"Muna Al Maslamani","email":"","orcid":"","institution":"Hamad Medical Corporation","correspondingAuthor":false,"prefix":"","firstName":"Muna","middleName":"Al","lastName":"Maslamani","suffix":""}],"badges":[],"createdAt":"2025-04-11 18:23:09","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6430500/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6430500/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s12879-025-12173-x","type":"published","date":"2026-01-23T15:59:20+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":82150221,"identity":"6f4d1403-44a0-4545-8d00-47414ee11d7b","added_by":"auto","created_at":"2025-05-07 07:14:49","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":29187,"visible":true,"origin":"","legend":"\u003cp\u003eRoc curve at AFB count at 2 months\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-6430500/v1/8dee7f6650c5db2d3d417f09.png"},{"id":101151838,"identity":"51beb35e-f49e-4fc5-8e73-602485effe23","added_by":"auto","created_at":"2026-01-26 16:06:35","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":484974,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6430500/v1/f8658a03-195f-4ecb-8dd3-760d51a773a5.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Culture Positivity and Predictors in Persistent Smear-Positive TB at Two Months","fulltext":[{"header":"Introduction","content":"\u003cp\u003ePulmonary tuberculosis (TB) is a major global health challenge, with airborne transmission being the primary mode of spread. Respiratory isolation is a commonly used public health measure to reduce TB transmission, but guidelines for its duration and implementation vary(\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e). The decline in smear positivity and infectivity following the initiation of effective treatment is well-documented, yet the timeline for patients to become noninfectious varies significantly (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e). The Centers for Disease Control and Prevention (CDC) recommends isolating patients until they achieve three consecutive negative sputum smears. (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e). Certain patients continue to test smear-positive for an extended time despite receiving effective treatment, necessitating prolonged isolation and the challenges that come with it. In some of these cases, smear positivity may only indicate the presence of non-viable bacilli, resulting in unnecessary isolation and a strain on resources. Prolonged isolation can have significant adverse effects on patients, including psychological distress, stigmatization, and socioeconomic challenges, particularly for marginalized populations(\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThis study sought to determine the proportion of culture-positive cases among patients remaining smear-positive after two months of treatment and, since two-month culture results take several weeks, to identify factors predicting culture-negative status in these persistently smear-positive patients. By addressing these objectives, we hope to contribute to the development of more nuanced isolation guidelines that balance infection control with patient well-being and resource optimization.\u003c/p\u003e"},{"header":"Methodology","content":"\u003cp\u003e A retrospective review of electronic medical records was conducted at a tertiary-level TB management center in Qatar from 1/1/2016 to 28/2/2024. The study included pulmonary TB patients who remained sputum smear-positive beyond two months of supervised, effective treatment under respiratory isolation. Data collected included demographics, disease extent (e.g., cavitary lesions on chest X-ray, disseminated disease), initial and two-month AFB smear counts, two-month AFB cultures and time to positivity, drug resistance profiles, comorbidities (e.g., diabetes, HIV, immunosuppression), and any treatment modifications.\u003c/p\u003e \u003cp\u003eThe AFB smear microscopy and culture was performed at the National TB Reference Laboratory, HMC, Qatar, which is a CAP accredited laboratory. The heat fixed AFB smear was prepared from NALC-NaOH treated sputum specimens; followed by staining using Fluorochrome (Auramine O) method for screening and Ziehl\u0026ndash;Neelsen (ZN) Method for confirmation of positive smears. The smears were examined under oil immersion and smear grading was performed as per WHO and CLSI guideline(\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e). The TB culture was conducted using the automated liquid culture BACTEC MGIT 960 system (BD, USA) following the manufacturer's instructions. Positive MGIT culture tubes were further analyzed through visual inspection, smear microscopy of the culture media, and the TBcID assay (BD, USA) to identify and confirm the presence of the Mycobacterium tuberculosis complex. TB treatment for drug susceptible and drug resistant TB were according to WHO guidelines (\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eThe statistical analysis was designed to evaluate the relationship between persistent smear positivity and culture status at two months of treatment, as well as to identify predictors of culture negativity. Categorical variables were displayed as counts and percentages, whereas normally distributed continuous variables were summarized as means and standard deviations. Non-normally distributed variables were represented by the median, 25th, and 75th percentiles. The Shapiro-Wilk test and histograms were employed to check data for normality. The T-test was used for normally distributed variables, and the Mann-Whitney test for non-parametric variables. Categorical variables were evaluated using the Chi-square test. Univariable analysis was performed to identify the potential predictors of culture conversion in smear positive patients. To evaluate the independent effect of each factor, multivariable logistic regression was applied. A ROC curve was then plotted to determine the optimal cutoff point where sensitivity and specificity were maximized. Using this cutoff, we created a confusion matrix to assess the ability of the AFB count in smear and presence of cavity in predicting culture conversion. Based on the findings, the newly identified predictor was added to a multivariable logistic regression model, along with the presence of lung cavity in initial chest x-ray, to help refine the predictive model and enhance classification accuracy. Statistical significance was considered as a two-tailed p-value less than 0.05. Stata/SE 14.2 was used for the analysis\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eThe study included 88 patients with persistent smear positivity beyond two months of treatment (Table \u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The median age was 41.5 years, and 84% were male. Mean AFB smear count in the initial smear was 650/100 fields, in chest x-ray, cavitary lesions were found in 67% (59/88), and bilateral or multi-lobar involvement in 84% (74/88). One patient had multidrug-resistant TB (MDR-TB), nine had isoniazid mono-resistance, and six had pyrazinamide mono-resistance. HIV co-infection was rare (1/88), while 32% (28/88) had uncontrolled diabetes.\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\u003ebaseline characteristics\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariable\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAll cohort (N\u0026thinsp;=\u0026thinsp;88)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSmear positive \u0026amp; culture negative (N\u0026thinsp;=\u0026thinsp;34)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSmear positive \u0026amp; culture positive (N\u0026thinsp;=\u0026thinsp;54)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003ep-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e41.5 (31.5\u0026ndash;49)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e43.00 (36.00\u0026ndash;50.00)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e40.50 (30.00\u0026ndash;48.00)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.48\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMale gender\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e74 (84%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e30 (88.24%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e44 (81.48%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMulti drug resistant MTB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1 ( 1.14%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0 ( 0.00%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1 ( 1.85%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.42\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePyrazinamide mono resistance\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6 ( 6.82%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2 ( 5.88%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4 ( 7.41%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.78\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIsoniazid mono resistance\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e9 ( 10.23%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2 ( 5.88%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e7 (12.96%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.29\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUncontrolled Diabetes mellitus\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e28 (31.82%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e12 (35.29%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e16 (29.63%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.58\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHIV positive\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1 ( 1.14%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1 ( 2.94%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0 ( 0.00%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCavity in the initial chest Xray\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e59 (67.05%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e16 (47.06%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e43 (79.63%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.002\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePlural effusion\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4 ( 4.55%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2 ( 5.88%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2 ( 3.70%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.63\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDisseminated TB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4 ( 4.55%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1 ( 2.94%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3 ( 5.56%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.57\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTreatment modification due to drug induced liver injury or drug rash\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10 ( 11.36%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2 ( 5.88%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e8 (14.81%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNumber of AFB in initial smear*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e650 (100\u0026ndash;2000)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e500 (100\u0026ndash;1000)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e900 (100\u0026ndash;2500)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.22\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDays taken of initial culture positivity*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.00 (\u003cspan additionalcitationids=\"CR7 CR8\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.00 (5.00\u0026ndash;11.00)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e7.00 (6.00\u0026ndash;9.00)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.59\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNumber of AFB in 2 months smear*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10 (5\u0026ndash;40)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5 (\u003cspan additionalcitationids=\"CR4 CR5 CR6 CR7 CR8 CR9 CR10 CR11 CR12 CR13 CR14\" citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e20 (5\u0026ndash;50)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003edays taken of 2 months culture positivity*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e29 (22\u0026ndash;36)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e29 (22\u0026ndash;36)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"4\" nameend=\"c4\" namest=\"c1\"\u003e \u003cp\u003e* Nonparametric data presented as median (IQR), and n (%) for categorical measures\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eAfter two months of anti-TB treatment, 61.4% (54/88) of the cohort remained culture positive. In these patients, the mean time to culture positivity rose from 7 days at baseline to 29 days.\u003c/p\u003e \u003cp\u003eCompared to culture-negative patients, those who remained culture-positive at two months had a significantly higher prevalence of cavitary lesions in initial chest x-ray (79% vs. 47%, p\u0026thinsp;=\u0026thinsp;0.002) and higher AFB counts in two-month-smears (20/100 fields vs. 5/100 fields, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). ROC curve analysis (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) identified an AFB cutoff of 10/100 fields as predictive of two-month culture positivity (AUC: 71%, sensitivity: 63%, specificity: 74%). Patients without cavitary lesions and AFB\u0026thinsp;\u0026lt;\u0026thinsp;10/100 fields had a negative predictive value (NPV) of 69% for two-month culture negativity (OR for culture conversion was 7.72, 95% CI: 1.90-31.36, p\u0026thinsp;=\u0026thinsp;0.004). (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e)\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e\u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAdjusted OR (95% Conf. interval)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eP value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDiabetes mellitus\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.667 (0.213\u0026ndash;2.088)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.486\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAFB\u0026thinsp;\u0026gt;\u0026thinsp;10/100 field with presence of lung cavity\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.723(1.902\u0026ndash;31.359)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.004\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.971(0.929\u0026ndash;1.015)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.189\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIsoniazid monoresistance\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4.332(0.692\u0026ndash;27.138)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.117\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePyrazinamide monoresistance\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6.03(0.522\u0026ndash;69.637)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.15\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBilateral involvement in chest Xray\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.483(0.1471\u0026ndash;1.584)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.23\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDrug induced hepatitis\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.116(0.332\u0026ndash;13.507)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.428\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDays taken for initial culture positivity\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.861(0.729\u0026ndash;1.017)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.245\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eOur cohort comprised of high-burden pulmonary TB cases, as indicated by extensive radiographic changes and high initial AFB counts in sputum smears. Despite a clear treatment response evidenced by a decline in AFB count, 61.4% of persistent smear-positive patients remained culture-positive at two months, suggesting ongoing infectivity. This challenges the assumption that smear positivity during treatment solely reflects non-viable bacilli and highlights the need for a more thorough assessment of infectiousness.\u003c/p\u003e \u003cp\u003eWe found that patients without cavitary lesions and with low AFB counts were more likely to be culture-negative, suggesting they could end isolation earlier. This study contributes to understanding isolation in high-burden TB cases with persistent smear positivity, emphasizing the difficulty of balancing transmission prevention with the drawbacks of prolonged isolation in high-transmission settings.\u003c/p\u003e \u003cp\u003eData from diverse experimental studies suggest that infectiousness rapidly declines after effective treatment initiation, However, the exact duration of treatment required to render people with TB disease non-infectious remains uncertain(\u003cspan additionalcitationids=\"CR11 CR12\" citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e). The notion that tuberculosis infectivity decreases after two weeks of treatment, with bacilli considered non-viable, was a postulation rather than an evidence-based conclusion(\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e). Contrary to this, a prospective cohort study in Qatar evaluated culture conversion in smear-positive pulmonary tuberculosis patients after two weeks of treatment, finding that 95.7% remained culture-positive, suggesting persistent infectivity.(\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eWhile the National Tuberculosis Controllers Association (NTCA) guidelines suggest that patients on effective anti-TB treatment for at least five days may be considered noninfectious or low-risk for transmission, regardless of sputum smear or culture results, they also recommend extended respiratory isolation in high-risk settings\u0026mdash;such as those involving vulnerable groups like young children or immunosuppressed individuals\u0026mdash;though the ideal isolation duration remains unclear (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e). In hot and humid Middle Eastern countries, where people often spend extended periods in air-conditioned spaces with recirculated air, these factors emphasize the need for refined isolation protocols that minimize unnecessary patient burden while ensuring effective infection control.\u003c/p\u003e \u003cp\u003eIt can be argued that culture positivity confirms viable \u003cem\u003eMycobacterium tuberculosis\u003c/em\u003e but does not fully capture infectiousness, which also depends on cough dynamics and aerosol generation (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e). Newer tests, including cough aerosol culture, have been explored to predict treatment response and guide de-isolation. Studies show a rapid decrease in culture-positive MTB in cough aerosol on effective treatment (\u003cspan additionalcitationids=\"CR19 CR20 CR21\" citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e). However, it should be noted that recent studies showed that daily tidal breathing can generate higher bacillary count than cough per 24 hours(\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eTranscriptomic analysis of bacterial RNA released into the environment has been investigated as a way to study the decrease in infectiousness. Research indicates that within four days of starting treatment, bacterial mRNA levels decrease by more than 98%, indicating a swift decline in the number of viable bacilli (\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e). Furthermore, transcriptional profiling shows a reduction in the expression of genes linked to virulence and pathogenicity, implying that \u003cem\u003eM. tuberculosis\u003c/em\u003e becomes less capable of initiating new infections (\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eSince culture takes several weeks, a faster technique to assess bacterial viability is fluorescein diacetate vital staining. This technique identifies viable bacteria with preserved membrane integrity and has been proposed as a way to detect treatment failure before culture results are available. (\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eA limitation of this study is that, although culture positivity confirms viable M. tuberculosis, it does not directly imply active transmission. Animal model studies could help assess the transmissibility of these viable bacilli, potentially refining infection control protocols and treatment efficacy assessments. Furthermore, the modest sample size of 88 patients may restrict the generalizability of these findings to the broader tuberculosis population.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn our study of high-burden TB cases with persistent smear positivity beyond two months, we found that the majority remained culture-positive, indicating the presence of viable \u003cem\u003eM. tuberculosis\u003c/em\u003e and a potential risk of transmission. This underscores the need for continued precautions, even though the psychological adverse effects of prolonged isolation should be considered. Further research is necessary to refine our understanding of transmission risk and optimize isolation protocols.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eType of study- Retrospective descriptive study\u003c/p\u003e\n\u003cp\u003e \u003cstrong\u003e \u003cb\u003eEthics approval and Consent to participate\u003c/b\u003e:\u003c/strong\u003e \u003cp\u003e Study was approved by the Institutional Review Board, which is the ethical committee of Medical Research Center, Hamad medical corporation, Doha, Qatar. Patient Consent Statement is not applicable as there is no patient identifiable data. Exempted from written informed consent from study participants by the Institutional Review Board.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eClinical Trial number\u003c/strong\u003e \u003cp\u003eNot applicable\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eConsent for publication:\u003c/strong\u003e \u003cp\u003eInstitutional consent obtained for publication\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eFunding:\u003c/h2\u003e \u003cp\u003eQatar national library funding for publication.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eJunais Koleri: Study design, data collection, data analysis, manuscript writing, corresponding author.Faraj S Howady : Study design, manuscript writingJay PN Singh : Manuscript writing Sara Al Balushi : Statistical analysis, Manuscript writing Muna Al Maslamani: Study design\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eAnusha Abdulkhader ([email protected] ) - Data retrieval.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe datasets used and analyzed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eWorld Health Organization. WHO guidelines on tuberculosis infection prevention and control: 2019 update [Internet]. Geneva: World Health Organization. 2019 [cited 2025 Feb 25]. Available from: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://iris.who.int/handle/10665/311259\u003c/span\u003e\u003cspan address=\"https://iris.who.int/handle/10665/311259\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDharmadhikari AS, Mphahlele M, Venter K, Stoltz A, Mathebula R, Masotla T, et al. Rapid impact of effective treatment on transmission of multidrug-resistant tuberculosis. Int J Tuberc Lung Dis Off J Int Union Tuberc Lung Dis. 2014;18(9):1019\u0026ndash;25.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRiley RL. Aerial dissemination of pulmonary tuberculosis. Am Rev Tuberc. 1957;76(6):931\u0026ndash;41.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGuidelines for Preventing the Transmission of Mycobacterium tuberculosis in Health-Care Facilities. 1994 [Internet]. [cited 2024 May 26]. Available from: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.cdc.gov/mmwr/preview/mmwrhtml/00035909.htm\u003c/span\u003e\u003cspan address=\"https://www.cdc.gov/mmwr/preview/mmwrhtml/00035909.htm\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCooper R, Williams M, Fennelly KP. Abandon the Acid-Fast Bacilli Smear for Patients With TB on Effective Treatment. Chest. 2023;164(1):21\u0026ndash;3.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNathavitharana RR, Pearl A, Biewer A, Young L, Mukasa L, Delrooz N, et al. Effects of Respiratory Isolation for Tuberculosis to Reduce Community-based Transmission: A Systematic Review. Clin Infect Dis. 2025;80(1):189\u0026ndash;98.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eForbes BA, Miller MB, Banaei N, Brown-Elliott BA, Das S, Salfinger M et al. Laboratory Detection and Identification of Mycobacteria.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNarvaiz de Kantor I, Kim SJ, Frieden TR, Laszlo A, Luelmo F, Norval PY et al. Laboratory services in tuberculosis control. 1998 [cited 2025 Mar 4]; Available from: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://iris.who.int/handle/10665/65942\u003c/span\u003e\u003cspan address=\"https://iris.who.int/handle/10665/65942\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWHO consolidated guidelines on tuberculosis. module 4: treatment: drug-resistant tuberculosis treatment [Internet]. [cited 2025 Mar 18]. Available from: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.who.int/publications/i/item/9789240007048\u003c/span\u003e\u003cspan address=\"https://www.who.int/publications/i/item/9789240007048\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShah M, Dansky Z, Nathavitharana R, Behm H, Brown S, Dov L et al. National Tuberculosis Coalition of America (NTCA) Guidelines for Respiratory Isolation and Restrictions to Reduce Transmission of Pulmonary Tuberculosis in Community Settings. Clin Infect Dis. 2024;ciae199.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRiley RL. The contagiosity of tuberculosis. Schweiz Med Wochenschr. 1983;113(3):75\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eEscombe AR, Moore DAJ, Gilman RH, Pan W, Navincopa M, Ticona E, et al. The Infectiousness of Tuberculosis Patients Coinfected with HIV. PLOS Med. 2008;5(9):e188.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNardell Ea, Stoltz A, de Kock E, Nathavitharana R, Jensen P, Mendel C et al. Measuring the Early Impact on Transmission of New Treatment Regimens for Drug Resistant Tuberculosis. In: C27 TB TREATMENT [Internet]. American Thoracic Society; 2019 [cited 2025 Feb 23]. pp. A7387\u0026ndash;A7387. (American Thoracic Society International Conference Abstracts). Available from: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.atsjournals.org/doi/\u003c/span\u003e\u003cspan address=\"https://www.atsjournals.org/doi/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1164/ajrccm-conference.2019.199.1_MeetingAbstracts.A7387\u003c/span\u003e\u003cspan address=\"10.1164/ajrccm-conference.2019.199.1_MeetingAbstracts.A7387\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRouillon A, Perdrizet S, Parrot R. Transmission of tubercle bacilli: The effects of chemotherapy. Tubercle. 1976;57(4):275\u0026ndash;99.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAlhowady F, Elmaki N, Ali M, Husain A, Al-Maslamani M, Alsuwaidi Z, et al. 794. Infectivity of Smear-Positive Pulmonary TB After 2 Weeks of Rifampicin-based Anti-Tuberculous Therapy. Open Forum Infect Dis. 2018;5(Suppl 1):S285\u0026ndash;6.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCalderwood CJ, Wilson JP, Fielding KL, Harris RC, Karat AS, Mansukhani R, et al. Dynamics of sputum conversion during effective tuberculosis treatment: A systematic review and meta-analysis. PLoS Med. 2021;18(4):e1003566.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAl-Moamary MS, Black W, Bessuille E, Elwood RK, Vedal S. The significance of the persistent presence of acid-fast bacilli in sputum smears in pulmonary tuberculosis. Chest. 1999;116(3):726\u0026ndash;31.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFennelly KP, Jones-L\u0026oacute;pez EC, Ayakaka I, Kim S, Menyha H, Kirenga B, et al. Variability of infectious aerosols produced during coughing by patients with pulmonary tuberculosis. Am J Respir Crit Care Med. 2012;186(5):450\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTheron G, Limberis J, Venter R, Smith L, Pietersen E, Esmail A, et al. Bacterial and host determinants of cough aerosol culture-positivity in patients with drug-resistant versus drug-susceptible tuberculosis. Nat Med. 2020;26(9):1435\u0026ndash;43.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNduba V, Njagi LN, Murithi W, Mwongera Z, Byers J, Logioia G, et al. Mycobacterium tuberculosis cough aerosol culture status associates with host characteristics and inflammatory profiles. Nat Commun. 2024;15(1):7604.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJones-L\u0026oacute;pez EC, Kim S, Fregona G, Marques-Rodrigues P, Hadad DJ, Molina LPD, et al. Importance of Cough and M. tuberculosis Strain Type as Risks for Increased Transmission within Households. PLoS ONE. 2014;9(7):e100984.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBasu S, Andrews JR, Poolman EM, Gandhi NR, Shah NS, Moll A, et al. Prevention of nosocomial transmission of extensively drug-resistant tuberculosis in rural South African district hospitals: an epidemiological modelling study. Lancet Lond Engl. 2007;370(9597):1500\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDinkele R, Gessner S, McKerry A, Leonard B, Leukes J, Seldon R et al. Aerosolization of Mycobacterium tuberculosis by Tidal Breathing. Am J Respir Crit Care Med 206(2):206\u0026ndash;16.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTranscriptional Adaptation of Drug-tolerant Mycobacterium tuberculosis During Treatment of Human Tuberculosis. | The Journal of Infectious Diseases | Oxford Academic [Internet]. [cited 2025 Feb 25]. Available from: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://academic.oup.com/jid/article/212/6/990/984852\u003c/span\u003e\u003cspan address=\"https://academic.oup.com/jid/article/212/6/990/984852\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShaikh A, Sriraman K, Vaswani S, Oswal V, Rao S, Mistry N. Early phase of effective treatment induces distinct transcriptional changes in Mycobacterium tuberculosis expelled by pulmonary tuberculosis patients. Sci Rep. 2021;11(1):17812.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKvach JT, Veras JR. A fluorescent staining procedure for determining the viability of mycobacterial cells. Int J Lepr Mycobact Dis Off Organ Int Lepr Assoc. 1982;50(2):183\u0026ndash;92.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eVan Deun A, Maug AKJ, Hossain A, Gumusboga M, de Jong BC. Fluorescein diacetate vital staining allows earlier diagnosis of rifampicin-resistant tuberculosis. Int J Tuberc Lung Dis Off J Int Union Tuberc Lung Dis. 2012;16(9):1174\u0026ndash;9.\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":"[email protected]","identity":"bmc-infectious-diseases","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"infd","sideBox":"Learn more about [BMC Infectious Diseases](http://bmcinfectdis.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/infd","title":"BMC Infectious Diseases","twitterHandle":"#bmcinfectdis","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Pulmonary TB, smear positivity, culture status, respiratory isolation, TB infectivity","lastPublishedDoi":"10.21203/rs.3.rs-6430500/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6430500/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIntroduction: In pulmonary tuberculosis (TB), smear positivity and infectivity typically decrease quickly with effective treatment, but the time required to become non-infectious varies, affecting the duration of respiratory isolation. The CDC recommends isolation until patients produce three consecutive negative sputum smears. However, it’s suggested that patients who remain smear-positive despite treatment may be shedding only non-viable bacilli, questioning the need for prolonged isolation until smear negativity is achieved. In patients remaining smear-positive after two months of therapy, we aim to evaluate this hypothesis by conducting sputum cultures to assess the viability of bacilli in their smears.\u003c/p\u003e\n\u003cp\u003eAim: This study aimed to (1) determine the proportion of culture-positive cases among pulmonary tuberculosis patients remaining smear-positive at two months of treatment and (2) identify factors predictive of culture-negative status to support earlier isolation discontinuation.\u003c/p\u003e\n\u003cp\u003eMethodology: A retrospective review of electronic medical records (2016–2024) was conducted at a tertiary TB center in Qatar, targeting patients smear-positive at two months. Data included demographics, disease extent (e.g., cavitary lesions), initial and two-month acid-fast bacilli (AFB) smear counts, two-month AFB cultures, drug resistance, and comorbidities.\u003c/p\u003e\n\u003cp\u003eResults: We identified 88 patients who remained smear-positive at two months of treatment. Among them, 61.4% were culture positive. Patients without cavitary lesions on the initial chest X-ray and those with two-month AFB counts \u0026lt;10/100 fields had a 69% negative predictive value for culture negativity.\u003c/p\u003e\n\u003cp\u003eConclusions: Over half of persistent smear-positive patients remain potentially infectious at two months. However, those without cavitary lesions and with low AFB counts could be candidates for earlier isolation discontinuation, optimizing resources and reducing patient burden. This study suggests refining isolation protocols using clinical and microbiological predictors of infectivity.\u003c/p\u003e","manuscriptTitle":"Culture Positivity and Predictors in Persistent Smear-Positive TB at Two Months","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-05-07 07:14:45","doi":"10.21203/rs.3.rs-6430500/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-06-19T04:29:20+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-06-05T13:55:58+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-05-30T07:17:04+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"114566889813088529232980081447533840825","date":"2025-05-28T17:12:29+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-05-23T21:56:01+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-05-22T06:52:48+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"71171164799866281448852241445219440123","date":"2025-05-20T13:43:07+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"269109765410858159128735722592479180239","date":"2025-05-19T06:49:07+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"170900156599284421885659554219321490068","date":"2025-05-12T10:54:50+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"144915776229349521705839978048276094876","date":"2025-05-03T07:12:44+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"300973340782017450784611519274997496954","date":"2025-04-29T09:45:17+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-04-29T08:43:10+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-04-16T01:39:29+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-04-16T01:39:21+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Infectious Diseases","date":"2025-04-11T18:10:52+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-infectious-diseases","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"infd","sideBox":"Learn more about [BMC Infectious Diseases](http://bmcinfectdis.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/infd","title":"BMC Infectious Diseases","twitterHandle":"#bmcinfectdis","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"9d031783-8b58-4d69-90d9-3a8ce7d6ef7f","owner":[],"postedDate":"May 7th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2026-01-26T16:02:50+00:00","versionOfRecord":{"articleIdentity":"rs-6430500","link":"https://doi.org/10.1186/s12879-025-12173-x","journal":{"identity":"bmc-infectious-diseases","isVorOnly":false,"title":"BMC Infectious Diseases"},"publishedOn":"2026-01-23 15:59:20","publishedOnDateReadable":"January 23rd, 2026"},"versionCreatedAt":"2025-05-07 07:14:45","video":"","vorDoi":"10.1186/s12879-025-12173-x","vorDoiUrl":"https://doi.org/10.1186/s12879-025-12173-x","workflowStages":[]},"version":"v1","identity":"rs-6430500","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6430500","identity":"rs-6430500","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}