Shamputa Isdore C, Jugheli Levan, Sadradze Nikoloz, Willery Eve, Portaels Françoise, Supply Philip, Rigouts Leen
Prince Leopold Institute of Tropical Medicine, Mycobacteriology Unit, Nationalestraat 155, B-2000 Antwerp, Belgium.
Respir Res. 2006 Jul 17;7(1):99. doi: 10.1186/1465-9921-7-99.
Studies on recurrent tuberculosis (TB), TB molecular epidemiology and drug susceptibility testing rely on the analysis of one Mycobacterium tuberculosis isolate from a single sputum sample collected at different disease episodes. This scheme rests on the postulate that a culture of one sputum sample is homogeneous and representative of the total bacillary population in a patient.
We systematically analysed several pre-treatment isolates from each of 199 smear-positive male adult inmates admitted to a prison TB hospital by standard IS6110 DNA fingerprinting, followed by PCR typing based on multiple loci containing variable number of tandem repeats (VNTRs) on a subset of isolates. Drug susceptibility testing (DST) was performed on all isolates for isoniazid, rifampicin, streptomycin and ethambutol.
We found mixed infection in 26 (13.1%) cases. In contrast, analysis of a single pre-treatment isolate per patient would have led to missed mixed infections in all or 14 of these 26 cases by using only standard DNA fingerprinting or the PCR multilocus-based method, respectively. Differences in DST among isolates from the same patient were observed in 10 cases, of which 6 were from patients with mixed infection.
These results suggest that the actual heterogeneity of the bacillary population in patients, especially in high TB incidence settings, may be frequently underestimated using current analytical schemes. These findings have therefore important implications for correct interpretation and evaluation of molecular epidemiology data and in treatment evaluations.
复发性结核病、结核病分子流行病学及药敏试验的研究依赖于对在不同疾病发作期采集的单个痰标本中分离出的一株结核分枝杆菌进行分析。该方案基于这样一个假设，即一个痰标本的培养物是均匀的，并且代表了患者体内总的杆菌菌群。
我们通过标准的IS6110 DNA指纹图谱技术，对一家监狱结核病医院收治的199名涂片阳性成年男性囚犯的每个患者的多个治疗前分离株进行了系统分析，随后对一部分分离株基于包含可变数量串联重复序列（VNTRs）的多个位点进行了PCR分型。对所有分离株进行了异烟肼、利福平、链霉素和乙胺丁醇的药敏试验（DST）。
我们发现26例（13.1%）存在混合感染。相比之下，若对每位患者仅分析一个治疗前分离株，那么通过仅使用标准DNA指纹图谱技术或基于PCR多位点的方法，将分别导致这26例中的全部或14例混合感染被漏检。在10例患者中观察到同一患者不同分离株之间药敏试验结果存在差异，其中6例来自混合感染患者。
这些结果表明，使用当前的分析方案，患者体内杆菌菌群的实际异质性，尤其是在结核病高发环境中，可能经常被低估。因此，这些发现对于正确解释和评估分子流行病学数据以及治疗评估具有重要意义。
