Background

Tuberculosis remains a worldwide public health emergency. To better understand M. tuberculosis and to identify genomic variations characteristic to the Indian clinical isolates by a low-cost method, a genomic subtractive hybridization between M. tuberculosis H37Rv and a clinical isolate from South India was performed.

Results

This revealed a novel 0.4-kb subtractive fragment which was used as a handle to pull out a 4.5-kb genomic region characteristic to the clinical isolate and was absent in H37Rv. On further studies, this 4.5-kb region was found to be present in 91% of the M. tuberculosis clinical isolates screened from Kerala, a state in South India. Interestingly, this novel region has 99% identity (with 100% query coverage) with genomic regions of M. canettii.

Discussion

The present study hypothesizes that this locus was present in the recent common environmental ancestor of mycobacteria, retained to the maximum extent in M. canettii and ancestral isolates of M. tuberculosis, and later deleted in other modern lineages of M. tuberculosis. Thus, this region may serve as one of the links between the pathogenic mycobacteria and the environmental species. We also propose that the Indian isolates of M. tuberculosis might be closely related to the putative progenitor M. prototuberculosis with respect to this locus. More studies on other genomic loci from different strains of M. tuberculosis are required to establish more links in this direction.

中文翻译：

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来自印度的结核分枝杆菌临床分离株的祖传基因组位点暗示了与卡尼分枝杆菌的遗传联系。

背景

结核病仍然是世界范围内的突发公共卫生事件。为了更好地了解结核分枝杆菌并通过低成本方法鉴定印度临床分离株的特征基因组变异，在结核分枝杆菌H37Rv和来自印度南部的临床分离株之间进行了基因组减性杂交。

结果

这揭示了一个新的0.4-kb的减性片段，该片段被用作拉出该临床分离株特征性的4.5-kb的基因组区域的手柄，并且在H37Rv中不存在。在进一步的研究中，从印度南部的喀拉拉邦筛选出的结核分枝杆菌临床分离株中，有91％存在这个4.5 kb的区域。有趣的是，该新颖区域与卡奈特氏菌的基因组区域具有99％的同一性（查询覆盖率为100％）。

讨论区

本研究假设该基因座存在于最近的分枝杆菌的常见环境祖先中，最大程度地保留在canettii结核分枝杆菌和结核分枝杆菌的祖先分离株中，随后在其他现代结核分枝杆菌中删除。因此，该区域可以用作致病性分枝杆菌与环境物种之间的联系之一。我们还建议印度分离结核分枝杆菌可能是密切相关的假定的祖M. prototuberculosis相对于该位点。需要对来自不同结核分枝杆菌菌株的其他基因组基因座进行更多研究，以建立该方向的更多联系。