Department of Science and Innovation/National Research Foundation Centre of Excellence for Biomedical TB Research, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand and the National Health Laboratory Service, Johannesburg, South Africa.
Department of Biology, Stanford University, Stanford, CA, United States.
Front Cell Infect Microbiol. 2023 Sep 6;13:1186191. doi: 10.3389/fcimb.2023.1186191. eCollection 2023.
Oral and/or tongue swabs have demonstrated ability to detect in adults with pulmonary tuberculosis (TB). Swabs provide useful alternative specimens for diagnosis of TB using molecular assays however, the diagnostic pickup by culture requires further improvement and development. Several studies identified the presence of differentially culturable tubercle bacilli (DCTB) populations in a variety of clinical specimens. These organisms do not grow in routine laboratory media and require growth factors in the form of culture filtrate (CF) from logarithmic phase cultures of H37Rv.
Herein, we compared the diagnostic performance of sputum and tongue swabs using Mycobacterial Growth Indicator Tube (MGIT) assays, Auramine smear, GeneXpert and DCTB assays supplemented with or without CF.
From 89 eligible participants, 83 (93%), 66 (74%) and 79 (89%) were sputum positive by MGIT, smear and GeneXpert, respectively. The corresponding tongue swabs displayed a lower sensitivity with 39 (44%), 2 (2.0%) and 18 (20%) participants respectively for the same tests. We aimed to improve the diagnostic yield by utilizing DCTB assays. Sputum samples were associated with a higher positivity rate for CF-augmented DCTB at 82/89 (92%) relative to tongue swabs at 36/89 (40%). Similarly, sputum samples had a higher positivity rate for DCTB populations that were CF-independent at 64/89 (72%) relative to tongue swabs at 26/89 (29%). DCTB positivity increased significantly, relative to MGIT culture, for tongue swabs taken from HIV-positive participants. We next tested whether the use of an alternative smear stain, DMN-Trehalose, would improve diagnostic yield but noted no substantial increase.
Collectively, our data show that while tongue swabs yield lower bacterial numbers for diagnostic testing, the use of growth supplementation may improve detection of TB particularly in HIV-positive people but this requires further interrogation in larger studies.
口腔和/或舌拭子已被证明能够检测到成人肺结核（TB）。拭子为使用分子检测方法诊断 TB 提供了有用的替代标本，但是培养物的诊断效果需要进一步提高和发展。几项研究在各种临床标本中发现了差异可培养结核分枝杆菌（DCTB）群体的存在。这些生物体在常规实验室培养基中无法生长，需要以 H37Rv 对数期培养物的培养滤液（CF）的形式提供生长因子。
本文比较了使用分枝杆菌生长指示管（MGIT）检测、金胺染色、GeneXpert 检测以及添加或不添加 CF 的 DCTB 检测的痰和舌拭子的诊断性能。
从 89 名合格参与者中，MGIT、金胺染色和 GeneXpert 检测分别有 83（93%）、66（74%）和 79（89%）名参与者的痰样本呈阳性。相应的舌拭子显示出较低的敏感性，对于相同的检测，分别有 39（44%）、2（2.0%）和 18（20%）名参与者为阳性。我们旨在通过利用 DCTB 检测来提高诊断率。与舌拭子相比，CF 增强的 DCTB 检测中，89 例痰样本中 82 例（92%）与 CF 相关，显示出更高的阳性率。同样，CF 独立的 DCTB 群体在 89 例痰样本中，阳性率为 64/89（72%），而在 89 例舌拭子中，阳性率为 26/89（29%）。与 MGIT 培养相比，DCTB 阳性率在 HIV 阳性参与者的舌拭子中显著增加。接下来，我们测试了是否使用替代的染色剂 DMN-海藻糖可以提高诊断率，但没有发现明显增加。
总的来说，我们的数据表明，虽然舌拭子在诊断检测中产生的细菌数量较低，但使用生长补充剂可能会提高 TB 的检测率，特别是在 HIV 阳性人群中，但这需要在更大的研究中进一步研究。
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