McIvor Amanda, Gordhan Bhavna Gowan, Waja Ziyaad, Otwombe Kennedy, Martinson Neil A, Kana Bavesh Davandra
DST/NRF Centre of Excellence for Biomedical TB Research, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand and the National Health Laboratory Service, South Africa.
Perinatal HIV Research Unit (PHRU), University of the Witwatersrand, Johannesburg, South Africa.
Tuberculosis (Edinb). 2021 Jul;129:102103. doi: 10.1016/j.tube.2021.102103. Epub 2021 Jun 12.
While some healthcare systems have shifted to molecular diagnostics, culture still remains the gold standard for tuberculosis diagnosis, but it is limited by its long duration to a positive result. Methods to reduce time to culture positivity (TTP) are urgently required. We determined if growth factor supplementation in the mycobacterial growth indicator tube (MGIT) culture system reduces TTP. MGITs were supplemented with fresh culture filtrate (CF) as a source of growth stimulatory molecules from axenic Mycobacterium tuberculosis culture. Different volumes of CF and media components were tested. The performance of these modified MGITs was assessed with sputum from HIV-TB co-infected individuals. Reducing the volume of MGIT cultures and removal of detergent from cultures grown to generate CF had a marginal but significant benefit on reducing TTP. In a subset of specimens, CF inhibited growth. Following optimization of methods, a reduced TTP occurred in specimens with low bacillary load as measured by GeneXpert, smear microscopy and colony forming units. Three specimens that were negative under standard conditions flagged positive following CF supplementation. Our data provide preliminary evidence that addition of CF to MGIT cultures can enhance detection of M. tuberculosis in HIV-TB co-infected patients with low sputum bacillary loads.
虽然一些医疗保健系统已转向分子诊断，但培养仍然是结核病诊断的金标准，但其受限于获得阳性结果的时间较长。迫切需要缩短培养阳性时间（TTP）的方法。我们确定了在分枝杆菌生长指示管（MGIT）培养系统中添加生长因子是否能缩短TTP。MGIT中添加了新鲜培养滤液（CF），作为来自无菌结核分枝杆菌培养物的生长刺激分子来源。测试了不同体积的CF和培养基成分。用HIV-TB合并感染个体的痰液评估这些改良MGIT的性能。减少MGIT培养物的体积以及从用于生成CF的培养物中去除去污剂，对缩短TTP有微小但显著的益处。在一部分标本中，CF抑制生长。在方法优化后，通过GeneXpert、涂片显微镜检查和菌落形成单位测量，低菌量标本的TTP缩短。三个在标准条件下为阴性的标本在添加CF后标记为阳性。我们的数据提供了初步证据，表明在MGIT培养物中添加CF可以提高对HIV-TB合并感染且痰液菌量低的患者中结核分枝杆菌的检测率。
