Department of Science and Technology/National Research Foundation Centre of Excellence for Biomedical Tuberculosis (TB) Research, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand and the National Health Laboratory Service, Johannesburg, South Africa.
Centre for the AIDS Programme of Research in South Africa (CAPRISA), University of KwaZulu-Natal, Durban, South Africa.
Front Cell Infect Microbiol. 2022 Sep 9;12:949370. doi: 10.3389/fcimb.2022.949370. eCollection 2022.
Several studies described the presence of non-replicating, drug-tolerant differentially culturable tubercle bacteria (DCTB) in sputum from patients with active tuberculosis (TB). These organisms are unable to form colonies on agar but can be recovered in liquid media supplemented with culture filtrate as a source of growth factors. Herein, we undertook to investigate the response of DCTB during the treatment of individuals with drug-resistant TB. A cohort of 100 participants diagnosed with rifampicin-resistant TB were enrolled and prospectively followed to monitor response to therapy using routine culture and limiting dilution assays, supplemented with culture filtrate (CF) to quantify DCTB. Fifteen participants were excluded due to contamination, and of the remaining 85 participants, 29, 49, and 7 were infected with rifampicin mono-resistant (RMR), multidrug-resistant (MDR), or extremely drug-resistant (XDR) TB, respectively. Analysis of baseline sputum demonstrated that CF supplementation of limiting dilution assays detected notable amounts of DCTB. Prevalence of DCTB was not influenced by smear status or mycobacterial growth indicator tube time to positivity. CF devoid of resuscitation promoting factors (Rpfs) yielded a greater amount of DCTB in sputum from participants with MDR-TB compared with those with RMR-TB. A similar effect was noted in DCTB assays without CF supplementation, suggesting that CF is dispensable for the detection of DCTB from drug-resistant strains. The HIV status of participants, and CD4 count, did not affect the amount of DCTB recovered. During treatment with second-line drug regimens, the probability of detecting DCTB from sputum specimens in liquid media with or without CF was higher compared with colony forming units, with DCTB detected up to 16 weeks post treatment. Collectively, these data point to differences in the ability of drug-resistant strains to respond to CF and Rpfs. Our findings demonstrate the possible utility of DCTB assays to diagnose and monitor treatment response for drug-resistant TB, particularly in immune compromised individuals with low CD4 counts.
已有多项研究描述了在活动性肺结核（TB）患者的痰液中存在非复制、耐药物的可培养差异结核分枝杆菌（DCTB）。这些生物体无法在琼脂上形成菌落，但可以在补充有培养滤液作为生长因子来源的液体培养基中回收。在此，我们着手研究 DCTB 在耐多药结核病患者治疗过程中的反应。招募了一组 100 名诊断为利福平耐药结核病的参与者，并前瞻性随访，使用常规培养和有限稀释测定法监测治疗反应，补充培养滤液（CF）以定量 DCTB。由于污染，15 名参与者被排除在外，在剩余的 85 名参与者中，分别有 29、49 和 7 人感染了利福平单耐药（RMR）、多药耐药（MDR）或极端耐药（XDR）结核病。基线痰液分析表明，有限稀释测定法中 CF 的补充检测到了相当数量的 DCTB。DCTB 的流行率不受涂片状态或分枝杆菌生长指示管阳性时间的影响。与 RMR-TB 相比，CF 缺乏复苏促进因子（Rpfs）可从 MDR-TB 患者的痰液中获得更多的 DCTB。在没有 CF 补充的 DCTB 检测中也观察到了类似的效果，这表明 CF 对于检测耐药株的 DCTB 是可有可无的。参与者的 HIV 状态和 CD4 计数均不影响回收的 DCTB 量。在二线药物治疗方案治疗期间，与菌落形成单位相比，在含有或不含有 CF 的液体培养基中从痰液标本中检测到 DCTB 的概率更高，在治疗后 16 周仍可检测到 DCTB。总的来说，这些数据表明耐药菌株对 CF 和 Rpfs 的反应能力存在差异。我们的研究结果表明，DCTB 检测可能有助于诊断和监测耐药结核病的治疗反应，特别是在 CD4 计数较低的免疫受损个体中。
