Overexpression of inhA, but not kasA, confers resistance to isoniazid and ethionamide in Mycobacterium smegmatis, M-bovis BCG and M-tuberculosis
Overexpression of inhA, but not kasA, confers resistance to isoniazid and ethionamide in Mycobacterium smegmatis, M-bovis BCG and M-tuberculosis
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DOI：
10.1046/j.1365-2958.2002.03162.x
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发表时间：
2002-10-01
影响因子：
3.6
通讯作者：
Jacobs, WR
中科院分区：
文献类型：
--
作者：
Larsen, MH;Vilchèze, C;Jacobs, WR
结核分枝杆菌的inha和kasa基因分别被认为是编码抗生素异烟肼(INH)的主要靶点。先前研究过高表达的INHA或KASA是否会产生对异烟肼的抗性的研究得出了不同的结果。在这项工作中，表达inha或kasa基因的多拷贝质粒被转化到耻垢分枝杆菌、牛分枝杆菌和三个不同的结核分枝杆菌菌株中。转化子以及以前发表的带有多拷贝inha或kasab质粒的结核分枝杆菌菌株，测试了它们对异烟肼、乙硫酰胺(ETH)或硫代乳霉素(TLM)的抗性。含有inha质粒的分枝杆菌对异烟肼的抵抗力均匀增加20倍或更多，对乙基苯丙氨酸的抵抗力增加10倍或更多。相反，在这五个菌株中，Kasa质粒没有增加对异烟肼或乙酸乙酯的耐药性，但它确实对已知的Kasa抑制剂硫代乳霉素产生了耐药性。已知异烟肼可增加对异烟肼敏感的结核分枝杆菌株中Kasa的表达。利用分子信标技术对Inha和Kasa的mRNA水平进行量化，结果显示Inha和Kasa的mRNA水平升高与异烟肼耐药性相关，而Kasa的mRNA水平与INH耐药性无关。总之，对含有Inha或Kasa质粒的菌株的分析得出了相同的结论：过表达的Inha而不是Kasa，赋予了INH和ETH对耻垢分枝杆菌、卡介苗分枝杆菌和结核分枝杆菌的抗性。因此，在这三个物种中，INHA是INH和ETH的主要作用靶点。
The inhA and kasA genes of Mycobacterium tuberculosis have each been proposed to encode the primary target of the antibiotic isoniazid (INH). Previous studies investigating whether overexpressed inhA or kasA could confer resistance to INH yielded disparate results. In this work, multicopy plasmids expressing either inhA or kasA genes were transformed into M. smegmatis, M. bovis BCG and three different M. tuberculosis strains. The resulting transformants, as well as previously published M. tuberculosis strains with multicopy inhA or kasAB plasmids, were tested for their resistance to INH, ethionamide (ETH) or thiolactomycin (TLM). Mycobacteria containing inhA plasmids uniformly exhibited 20-fold or greater increased resistance to INH and 10-fold or greater increased resistance to ETH. In contrast, the kasA plasmid conferred no increased resistance to INH or ETH in any of the five strains, but it did confer resistance to thiolactomycin, a known KasA inhibitor. INH is known to increase the expression of kasA in INH-susceptible M. tuberculosis strains. Using molecular beacons, quantified inhA and kasA mRNA levels showed that increased inhA mRNA levels correlated with INH resistance, whereas kasA mRNA levels did not. In summary, analysis of strains harbouring inhA or kasA plasmids yielded the same conclusion: overexpressed inhA, but not kasA, confers INH and ETH resistance to M. smegmatis, M. bovis BCG and M. tuberculosis. Therefore, InhA is the primary target of action of INH and ETH in all three species.