Pham Ngoc Thach Tuberculosis and Lung Disease Hospital, Ho Chi Minh City, Vietnam.
J Clin Microbiol. 2012 May;50(5):1586-92. doi: 10.1128/JCM.00434-12. Epub 2012 Feb 29.
Tuberculosis patients may be infected with or have disease caused by more than one Mycobacterium tuberculosis strain, usually referred to as "mixed infections." These have mainly been observed in settings with a very high tuberculosis incidence and/or high HIV prevalence. We assessed the rate of mixed infections in a population-based study in rural Vietnam, where the prevalences of both HIV and tuberculosis are substantially lower than those in previous studies looking at mixed infections. In total, 1,248 M. tuberculosis isolates from the same number of patients were subjected to IS6110 restriction fragment length polymorphism (RFLP) typing, spoligotyping, and variable-number-tandem-repeat (VNTR) typing. We compared mixed infections identified by the presence of (i) discrepant RFLP and spoligotype patterns in isolates from the same patient and (ii) double alleles at ≥ 2 loci by VNTR typing and assessed epidemiological characteristics of these infections. RFLP/spoligotyping and VNTR typing identified 39 (3.1%) and 60 (4.8%) mixed infections, respectively (Cohen's kappa statistic, 0.57). The number of loci with double alleles in the VNTR pattern was strongly associated with the proportion of isolates with mixed infections according to RFLP/spoligotyping (P < 0.001). Mixed infections occurred more frequently in newly treated than in previously treated patients, were significantly associated with minor X-ray abnormalities, and were almost significantly associated with lower sputum smear grades. Although the infection pressure in our study area is lower than that in previously studied populations, mixed M. tuberculosis infections do occur in rural South Vietnam in at least 3.1% of cases.
肺结核患者可能同时感染或患有多种结核分枝杆菌菌株引起的疾病，通常称为“混合感染”。这些主要在结核病发病率非常高和/或艾滋病毒流行率高的环境中观察到。我们在越南农村进行了一项基于人群的研究，评估了混合感染的发生率，该地区的艾滋病毒和结核病流行率均明显低于之前研究混合感染的地区。共有 1248 株来自相同数量患者的结核分枝杆菌分离株进行了 IS6110 限制片段长度多态性（RFLP）分型、 spoligotyping 和可变数串联重复（VNTR）分型。我们比较了通过相同患者的分离物中（i）存在不一致的 RFLP 和 spoligotype 模式以及（ii）VNTR 分型时至少 2 个位点的双等位基因来识别的混合感染，并评估了这些感染的流行病学特征。RFLP/spoligotyping 和 VNTR 分型分别鉴定出 39（3.1%）和 60（4.8%）的混合感染（Cohen's kappa 统计量为 0.57）。VNTR 模式中双等位基因的位点数量与根据 RFLP/spoligotyping 鉴定的混合感染分离物的比例密切相关（P < 0.001）。新治疗患者比既往治疗患者更常发生混合感染，与轻微的 X 线异常显著相关，与较低的痰涂片等级几乎显著相关。尽管我们研究区域的感染压力低于之前研究的人群，但在越南农村地区，混合结核分枝杆菌感染至少在 3.1%的病例中发生。
