Molecular Analysis of the embCAB Locus and embR Gene Involved in Ethambutol Resistance in Clinical Isolates of Mycobacterium tuberculosis in France
Molecular Analysis of the embCAB Locus and embR Gene Involved in Ethambutol Resistance in Clinical Isolates of Mycobacterium tuberculosis in France
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DOI：
10.1128/aac.00150-15
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发表时间：
2015-08-01
影响因子：
4.9
通讯作者：
Veziris, Nicolas
中科院分区：
文献类型：
--
作者：
Brossier, Florence;Sougakoff, Wladimir;Veziris, Nicolas
EmbB基因306位密码子的修饰被认为是导致结核分枝杆菌临床分离株对乙胺丁醇(ETB)耐药的主要机制。然而，据报道，embCAB基因和embR基因的许多其他突变与ETB耐药性有关。embB基因是该基因的转录激活因子。在这里，我们调查了来自法国的结核分枝杆菌复合分离株embCAB和emBR中观察到的核苷酸变异的多样性。对71株ETB耐药株(ETB-R)和60株ETB敏感株(ETB-S)进行了基因序列测定。131个分离株有12个对应于系统发育标记的突变。在60株ETB-S分离株中，只有3株(5%)存在非系统发育标志的非同义突变。在71株ETB-R分离株中，98%存在可能导致ETB耐药性的embCAB突变：70%的突变位于embB密码子306、406或497位；13%的突变位于密码子296和426之间的这三个位置之外；15%的突变对应于EMBC-EMBA基因间隔区的突变。我们发现结核分枝杆菌耐药性与embB和embc-emba基因间隔区突变的存在密切相关(P<；0.001)。而EMBC和EMBA中检测到的突变与ETB耐药无关，EMBR中也未检测到突变。这些结果有力地表明，通过检测密码子296和497之间的embB区，以及在-8和-21位之间加入EMBC-EMBA基因间隔区，可以提高基于embB密码子306检测ETB耐药性的诊断方法的敏感性。
Modification of codon 306 in embB is regarded as the main mechanism leading to ethambutol (ETB) resistance in clinical isolates of Mycobacterium tuberculosis. However, numerous mutations elsewhere in the embCAB locus and in embR, a putative transcriptional activator of this locus, have been reported to be involved in ETB resistance. Here, we investigated the diversity of nucleotide variations observed in embCAB and embR in M. tuberculosis complex isolates from France. These regions were sequenced in 71 ETB-resistant (ETB-R) and 60 ETB-susceptible (ETB-S) clinical isolates of known phylogenetic lineages. The 131 isolates had 12 mutations corresponding to phylogenetic markers. Among the 60 ETB-S isolates, only 3 (5%) had nonsynonymous mutations that were not phylogenetic markers. Among the 71 ETB-R isolates, 98% had mutations in embCAB that likely contribute to ETB resistance: 70% had mutations located in embB codon 306, 406, or 497; 13% had mutations located outside these three positions between codons 296 and 426; and 15% had mutations corresponding to mutations in the embC-embA intergenic region. We found a strong association between resistance to ETB and the presence of mutations in embB and the embC-embA intergenic region (P < 0.001). In contrast, the mutations detected in embC and embA were not involved in ETB resistance, and no mutation was detected in embR. These results strongly suggest that the sensitivity of diagnostic assays for detecting ETB resistance based on testing of embB codon 306 can be increased by testing of the embB region between codons 296 and 497 and by including the embC-embA intergenic region between positions -8 and -21.