Minor contribution of mutations at iniA codon 501 and embC-embA intergenic region in ethambutol-resistant clinical Mycobacterium tuberculosis isolates in Kuwait

Jaber, Al-Anoud; Ahmad, Suhail; Mokaddas, Eiman

doi:10.1186/1476-0711-8-2

Cited by 13 publications

(8 citation statements)

References 34 publications

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“…None of these mutations was observed in ETB-S isolates, and we found a strong statistical association between ETB resistance and mutations in the embC-embA intergenic region (P Ͻ 0.001). Excluding the -c11a mutation, the mutations at positions Ϫ8, Ϫ12, and Ϫ16 and the deletion of cg at positions Ϫ21 and Ϫ20, which are located within/adjacent to a predicted TATA box (15,16,53), were found in ETB-R strains carrying no other mutations involved in ETB resistance, confirming their involvement in ETB resistance. The role of the -c11a mutation is less clear because this mutation was identified in a strain that also has the EmbB M306I mutation, but Cui et al demonstrated that mutations in the embC-embA intergenic region (including -c11a) increase ETB resistance by enhancing the transcription of embA and embB, with the MICs of ETB for strains with both embC-embA intergenic region mutations and embB mutations being much higher than those for strains with only an embB mutation (53).…”

Section: Discussionmentioning

confidence: 69%

“…According to the literature, the proportion of ETB-R isolates carrying a mutation in the embC-embA intergenic region varies from 0 to 27% (5,15,16,20,46,53). In our study, 23% of ETB-R isolates had mutations at five positions in the embC-embA intergenic region, with a total of six distinct mutations: -c8a/t, -c11a, -c12t, -c16t, and a deletion of 2 nucleotides at positions Ϫ21 and Ϫ20.…”

Section: Discussionmentioning

confidence: 88%

“…Few publications have reported sequencing of the entire embCAB locus (16,20,46); most previous studies investigated only part of the embCAB locus (5,26), part of embC-embB and embR almost entirely (23), or the embC-embA intergenic region entirely and part of embB (15). In these studies, the percentage of ETB-R isolates with mutations in the embCAB locus ranged from 65% (16) to 96% (46).…”

Section: Discussionmentioning

confidence: 94%

“…These enzymes are essential for the synthesis of arabinogalactan (EmbA and EmbB) and lipoarabinomannan (EmbC) in the cell wall of Mycobacterium tuberculosis complex (MTBC) isolates (10,12). Although the embCAB locus is also called the emb-CAB operon, it is not a real operon because the promoter of embA and embB is thought to be located in the embC-embA intergenic region (85 bp) (15,16), and the promoter of embC is in the region upstream of embC, possibly in the Rv3792 gene (11,17), while the embR gene of MTBC isolates is located 2 Mb from the embCAB locus (18,19).…”

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confidence: 99%

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Molecular Analysis of the embCAB Locus and embR Gene Involved in Ethambutol Resistance in Clinical Isolates of Mycobacterium tuberculosis in France

Brossier

Sougakoff

Bernard

et al. 2015

Antimicrob Agents Chemother

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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 embCembA 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.

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Section: Discussionmentioning

confidence: 69%

Section: Discussionmentioning

confidence: 88%

Section: Discussionmentioning

confidence: 94%

mentioning

confidence: 99%

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Molecular Analysis of the embCAB Locus and embR Gene Involved in Ethambutol Resistance in Clinical Isolates of Mycobacterium tuberculosis in France

Brossier

Sougakoff

Bernard

et al. 2015

Antimicrob Agents Chemother

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“…Molecular DST has shown good performance in the diagnosis of rifampin resistance, but the sensitivity and specificity of embB-based molecular DST of EMB resistance are lower, suggesting that other gene mutations are involved in EMB resistance. Previous studies by several groups have detected mutations in embC-embA IGR in strains from the United States, the former Soviet Union, Kuwait, Germany, and Uzbekistan but found no epidemiological correlation of these mutations with EMB resistance, possibly due to there being fewer clinical strains showing mutations in embC-embA IGR (10,25,26). In this study, we found embC-embA IGR mutations in clinical EMB-resistant strains from east China, suggesting a wide distribution of embC-embA IGR mutations across the world.…”

Section: Discussionmentioning

confidence: 95%

Mutations in the embC-embA Intergenic Region Contribute to Mycobacterium tuberculosis Resistance to Ethambutol

Cui

Song

et al. 2014

Antimicrob Agents Chemother

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The rapid increase in Mycobacterium tuberculosis resistance to ethambutol (EMB) threatens the diagnosis and treatment of tuberculosis (TB). We investigated the role of mutations in the embC-embA intergenic region (IGR) in EMB-resistant clinical strains from east China. A total of 767 M. tuberculosis clinical strains were collected and analyzed for their drug susceptibility to EMB using the MGIT 960 system and MIC assay, and the embC-embA IGRs of these strains were sequenced. The transcriptional activity of the embC-embA IGR mutations was examined by reporter gene assays in recombinant Mycobacterium smegmatis strains, and the effect of IGR mutations on its binding to EmbR, a transcription regulator of embAB, was analyzed by gel mobility shift assays. Correlation coefficient analysis showed that the embC-embA IGR mutation is associated with EMB resistance. The clinical strains carrying IGR mutations had a much higher level of embA and embB mRNA as well as higher MICs to EMB. IGR mutations had higher transcriptional activity when transformed into M. smegmatis strains. Mutated IGRs bound to EmbR with much higher affinity than wild-type fragments. The sensitivity of molecular drug susceptibility testing (DST) with IGR mutations as an additional marker increased from 65.5% to 73.5%. Mutations of the embC-embA IGR enhance the binding of EmbR to the promoter region of embAB and increase the expression of embAB, thus contributing to EMB resistance. Therefore, identification of IGR mutations as markers of EMB resistance could increase the sensitivity of molecular DST.T uberculosis (TB) remains a major global health problem. It affects millions of people each year and is the second leading cause of death from an infectious disease worldwide. In 2012, an estimated 8.6 million people developed TB, and 1.3 million died from the disease. The emergence of drug-resistant strains of Mycobacterium tuberculosis, especially those that are multidrug resistant (MDR) and extensively drug resistant (XDR), has posed a serious threat to global TB control programs (1). An estimated 3.6% of new patients and 20.2% of previously treated patients have MDR-TB, and there were 450,000 new cases of MDR-TB worldwide in 2012 (2). Given the alarming rise of drug-resistant TB, the identification of drug resistance genes is critical for the detection and treatment of TB. Much progress has been made to identify gene mutations in specific loci of the M. tuberculosis genome as the molecular basis for TB drug resistance and as drug targets for the development of anti-TB drugs. Although an association of mutations in these resistance genes with drug resistance has been observed, the exact role these genes play in the development of drug resistance is not fully understood. Furthermore, a significant number of anti-TB drug-resistant strains do not carry these mutations, suggesting that unknown gene mutations or variations are involved in the development of anti-TB drug resistance.Ethambutol (EMB) is an essential first-line anti-TB drug that inhibits the biosy...

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Rapid detection of ethambutol-resistant genes in Mycobacterium tuberculosis clinical isolates

Liang

et al. 2010

Ann Microbiol

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An oligonucleotide probe has been designed and compounded for detecting the ethambutol (EMB) resistance gene of Mycobacterium tuberculosis. It was placed on a nitrocellulose membrane for use in the reverse dot-blot hybridization assay, with the PCR product labeled with biotin. Analysis was carried out on 82 M. tuberculosis clinical isolates. The results indicate that among the 31 EMB-sensitive strains, the single-strand conformational polymorphism (SSCP) spectrum and reverse dot-blot (RDB) assay results on the embB gene in 26 strains were completely identical to those of the standard strain (H37Rv), testing positive for E1 hybridization; the SSCP spectrum of the remaining five strains indicated that migration had occurred. Among the 51 EMB-resistant strains, 24 strains tested positive for E1 hybridization; of the remaining 27 strains, 18 strains tested positive for E1b hybridization, two tested positive for E1c hybridization, five tested positive for E1d hybridization, one tested positive for E1e hybridization, and one tested positive for E1f hybridization. The lowconcentration (64.70%) drug-resistant strains did not have the mutation at the codon 306 of embB. Among the 18 highconcentration drug-resistant strains, 15 strains tested positive for E1b hybridization, two tested positive for E1c hybridization, and one tested positive for E1f hybridization. The mutation detection rate was 52.94%. The RDB technology may be an easy and rapid method for detecting the codon 306 mutation of embB gene in some M. tuberculosis clinical isolates. We conclude that the ATG→GTG and ATG→CTG mutations of codon 306 of embB are one of the main causes of stron g EMB drug resistance in M. tuberculosis.

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Minor contribution of mutations at iniA codon 501 and embC-embA intergenic region in ethambutol-resistant clinical Mycobacterium tuberculosis isolates in Kuwait

Cited by 13 publications

References 34 publications

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

Mutations in the embC-embA Intergenic Region Contribute to Mycobacterium tuberculosis Resistance to Ethambutol

Rapid detection of ethambutol-resistant genes in Mycobacterium tuberculosis clinical isolates

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