Division of Anatomy and Histology, Faculty of Health Sciences, Tygerberg, Stellenbosch University, Stellenbosch, Western Cape, South Africa.
PLoS One. 2013 Jul 30;8(7):e70178. doi: 10.1371/journal.pone.0070178. Print 2013.
Molecular genotyping methods have shown infection with more than one Mycobacterium tuberculosis strain genotype in a single sputum culture, indicating mixed infection.
This study aimed to develop a PCR-based genotyping tool to determine the population structure of M. tuberculosis strain genotypes in primary Mycobacterial Growth Indicator Tubes (MGIT) and Löwenstein-Jensen (LJ) cultures to identify mixed infections and to establish whether the growth media influenced the recovery of certain strain genotypes.
A convenience sample of 206 paired MGIT and LJ M. tuberculosis cultures from pulmonary tuberculosis patients resident in Khayelitsha, South Africa were genotyped using an in-house PCR-based method to detect defined M. tuberculosis strain genotypes.
The sensitivity and specificity of the PCR-based method for detecting Beijing, Haarlem, S-family, and LAM genotypes was 100%, and 75% and 50% for detecting the Low Copy Clade, respectively. Thirty-one (15%) of the 206 cases showed the presence of more than one M. tuberculosis strain genotype. Strains of the Beijing and Haarlem genotypes were significantly more associated with a mixed infection (on both media) when compared to infections with a single strain (Beijing MGIT p = 0.02; LJ, p<0.01) and (Haarlem: MGIT p<0.01; LJ, p = 0.01). Strains with the Beijing genotype were less likely to be with "other genotype" strains (p<0.01) while LAM, Haarlem, S-family and LCC occurred independently with the Beijing genotype.
The PCR-based method was able to identify mixed infection in at least 15% of the cases. LJ media was more sensitive in detecting mixed infections than MGIT media, implying that the growth characteristics of M. tuberculosis on different media may influence our ability to detect mixed infections. The Beijing and Haarlem genotypes were more likely to occur in a mixed infection than any of the other genotypes tested suggesting pathogen-pathogen compatibility.
分子基因分型方法已经在单次痰培养物中发现了超过一种结核分枝杆菌菌株基因型的感染，表明存在混合感染。
本研究旨在开发一种基于 PCR 的基因分型工具，以确定原发性分枝杆菌生长指示剂管（MGIT）和 Löwenstein-Jensen（LJ）培养物中结核分枝杆菌菌株基因型的种群结构，以确定混合感染，并确定生长培养基是否影响某些菌株基因型的恢复。
从南非开普敦的肺结核患者中采集了 206 对 MGIT 和 LJ 结核分枝杆菌培养物的方便样本，使用内部基于 PCR 的方法对其进行基因分型，以检测定义的结核分枝杆菌菌株基因型。
基于 PCR 的方法检测北京、哈雷姆、S 家族和 LAM 基因型的灵敏度和特异性为 100%，检测低拷贝克隆的灵敏度和特异性分别为 75%和 50%。206 例中有 31 例（15%）存在一种以上的结核分枝杆菌菌株基因型。与单一菌株感染相比，北京和哈雷姆基因型的菌株更易发生混合感染（两种培养基均如此）（北京 MGIT p=0.02；LJ，p<0.01）和（哈雷姆：MGIT p<0.01；LJ，p=0.01）。北京基因型菌株与“其他基因型”菌株的相关性较低（p<0.01），而 LAM、哈雷姆、S 家族和 LCC 与北京基因型独立发生。
基于 PCR 的方法能够在至少 15%的病例中识别混合感染。与 MGIT 培养基相比，LJ 培养基更能检测到混合感染，这表明结核分枝杆菌在不同培养基上的生长特性可能影响我们检测混合感染的能力。与其他测试的基因型相比，北京和哈雷姆基因型更有可能发生混合感染，这表明病原体-病原体的相容性。
