Genetic characterisation of the ethambutol resistance-determining region in Mycobacterium tuberculosis: prevalence and significance of embB306 mutations

Perdigão, João; Macedo, Rita; Ribeiro, Ana Clara; Brum, Laura; Portugal, Isabel

doi:10.1016/j.ijantimicag.2008.09.021

Cited by 26 publications

(21 citation statements)

References 21 publications

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“…Although the association between embB306 mutation and EMB resistance has been identified, the exact role of embB306 mutations in the development of ethambutol resistance and multidrug resistance in M. tuberculosis is not fully understood. Since the majority of EMB resistance occurs in MDR strains of M. tuberculosis, it is likely that embB306 substitutions were not directly associated with ethambutol resistance but rather with MDR-TB, and it is concluded that embB306 mutations can serve as a marker for development of drug resistance [20,21].…”

Section: Discussionmentioning

confidence: 99%

Frequency of mutational changes in the embB among the ethambutol-resistant strains of Mycobacterium tuberculosis in Iran

Rezaei

Haeili

Mohajeri

et al. 2016

J Infect Dev Ctries

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Introduction: Early detection of drug resistant tuberculosis is one of the main priorities of TB control program. Ethambutol (EMB) is a firstline anti-TB drug that is effective for preventing treatment failures caused by Mycobacterium tuberculosis strains that are resistant to other drugs. The aim of this study was to sequence the embB gene to characterize the mutations causing resistance to EMB and to analyze the relationship between bacterial genotype and EMB resistance among M. tuberculosis isolates in Iran. Methodology: A total of 20 M. tuberculosis isolates comprising 10 multidrug-resistant (MDR) and 10 non-MDR isolates, recovered from TB patients in four regions: Tehran, Isfahan, Zahedan, Khorasan, were analyzed. Mutational profiling was performed by amplifying and sequencing the embB gene. Spoligotyping was carried out to characterize the bacterial genotype. Results: Phenotypic EMB resistance was found in 13 strains. Mutations affecting ethambutol resistance-determining region (ERDR) of the embB were identified in 6 of 13 EMB-resistant isolates. The majority of these mutations resulted in amino acid substitution at position 306 (M306V). A novel mutation at codon 366 was identified (S366L) in one isolate. Ural was the most predominant genotype in the studied population. Beijing genotype was associated with both MDR and EMB resistance in which all mutations occurred at codon 306 of the embB gene. Conclusion: A significant association between Beijing genotype and EMB resistance was found, mainly due to mutations at embB306. Results of this study can be used as a basis to develop or improve rapid molecular tests to monitor drug-resistant strains in this country.

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Section: Discussionmentioning

confidence: 99%

Frequency of mutational changes in the embB among the ethambutol-resistant strains of Mycobacterium tuberculosis in Iran

Rezaei

Haeili

Mohajeri

et al. 2016

J Infect Dev Ctries

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“…Some authors (38,(50)(51)(52) have argued that mutations at codon 306 in EmbB do not cause ETB resistance but predispose M. tuberculosis isolates to the development of drug resistance and increase the capacity of resistant isolates to be transmitted (38,(50)(51)(52). Accordingly, several reports have described isolates with mutations at codon 306 of EmbB that remain susceptible to ETB (2,4,8,13,17,25,29,30,34,36,46,51,52). There are two explanations for the presence of a mutation at codon 306 in EmbB in an ETB-S isolate: the ETB concentration recommended for drug susceptibility testing varies from 2 to 7.5 mg/liter depending on the phenotypic method used for susceptibility testing (39), and the ETB MICs induced by mutations in codon 306 could be close to the breakpoint defining ETB resistance (37,50).…”

Section: Discussionmentioning

confidence: 99%

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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“…There is accumulating evidence that high-level EMB resistance is a multistage process, requiring two or more independent mutations (20,23,28). EmbB mutations are often associated with high-level resistance in clinical isolates, but mutations in codon 306 are not sufficient on their own to generate high-level resistance (23), so presumably there are secondary mutations (which may be dependent on strains already having EmbB mutations).…”

Section: Discussionmentioning

confidence: 99%

The Arabinosyltransferase EmbC Is Inhibited by Ethambutol in Mycobacterium tuberculosis

Goude

Amin

Chatterjee

et al. 2009

Antimicrob Agents Chemother

119

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Ethambutol (EMB) is an antimycobacterial drug used extensively for the treatment of tuberculosis caused by Mycobacterium tuberculosis. EMB targets the biosynthesis of the cell wall, inhibiting the synthesis of both arabinogalactan and lipoarabinomannan (LAM), and is assumed to act via inhibition of three arabinosyltransferases: EmbA, EmbB, and EmbC. EmbA and EmbB are required for the synthesis of arabinogalactan, and at least one enzyme (M. tuberculosis EmbA [EmbA Mt ]) is essential in M. tuberculosis. EmbC Mt is also essential for the viability of M. tuberculosis but is involved in the synthesis of LAM. We show that mutations in EmbC Mt that reduce its arabinosyltransferase activity result in increased sensitivity to EMB and the production of smaller LAM species in M. tuberculosis. Overexpression of EmbC Mt was not tolerated in M. tuberculosis, but overexpression of Mycobacterium smegmatis EmbC (EmbC Ms ) led to EMB resistance and the production of larger LAM species in M. tuberculosis. Treatment of wild-type M. tuberculosis strains with EMB led to inhibition of LAM synthesis, resulting in the production of smaller species of LAM. In contrast, no change in LAM production was seen in EMB-resistant strains. Overexpression of EmbB Ms in M. tuberculosis also resulted in EMB resistance, but at a lower level than that caused by EmbC Ms . Overexpression of EmbA Mt in M. tuberculosis had no effect on EMB resistance. Thus, there is a direct correlation between EmbC activity and EMB resistance, as well as between EmbC activity and the size of the LAM species produced, confirming that EmbC is one of the cellular targets of EMB action.Tuberculosis (TB), one of the oldest diseases known to humans, remains a major public health threat. It is estimated that one-third of the world's population are infected with the causative agent, Mycobacterium tuberculosis. The scale of the problem is increasing, and the disease is becoming deadlier as it intersects with the spread of human immunodeficiency virus. The emergence of multidrug-resistant strains establishes the urgent need to fully understand the mechanisms of drug resistance. Ethambutol (EMB) is a bacteriostatic, antimycobacterial drug first described in 1961 (31) and has been prescribed for TB treatment since 1966. EMB is used worldwide for TB therapy in combination with isoniazid, pyrazinamide, and rifampin (rifampicin). It is also effective in the treatment of opportunistic mycobacterial infections of patients with human immunodeficiency virus. Unfortunately, resistance to EMB has been reported in as many as 4% of clinical isolates of M. tuberculosis and is prevalent among multidrug-resistant strains (5).The effects of EMB are highly pleiotropic, and over the past 40 years, many efforts have been made to understand its intracellular target(s). Kilburn and Greenberg (12) were the first to indicate that EMB treatment of Mycobacterium smegmatis caused rapid bacterial declumping, suggesting cell wall changes. It was subsequently demonstrated that EMB inhibited the transfer of m...

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Genetic characterisation of the ethambutol resistance-determining region in Mycobacterium tuberculosis: prevalence and significance of embB306 mutations

Cited by 26 publications

References 21 publications

Frequency of mutational changes in the embB among the ethambutol-resistant strains of Mycobacterium tuberculosis in Iran

Frequency of mutational changes in the embB among the ethambutol-resistant strains of Mycobacterium tuberculosis in Iran

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

The Arabinosyltransferase EmbC Is Inhibited by Ethambutol in Mycobacterium tuberculosis

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