Characteristics of embB mutations in multidrug-resistant Mycobacterium tuberculosis isolates in Henan, China

Abstract

ObjectivesTo determine the association between embB mutations and drug resistance, and to further investigate the mechanism of embB mutations involved in the development of ethambutol and multidrug resistance in Mycobacterium tuberculosis.MethodsOne hundred and thirty-eight multidrug-resistant clinical M. tuberculosis isolates, including 86 ethambutol-resistant and 52 ethambutol-susceptible strains, were analysed to characterize mutations within the entire coding region of the embB gene. Moreover, a two-step genotyping was performed to identify the genetic lineage.ResultsIn total, 27 embB mutation types were detected in 19 distinct codons. Though a strong association was observed between embB mutations and ethambutol resistance, 19.2% of embB306 mutants and 11.5% of embB406 or embB497 mutants were ethambutol susceptible. Among 39 ethambutol-resistant strains without embB306 mutations, 51.3% harboured mutations at codons 406 or 497. Particularly, three pairs of isolates with identical embB mutations and genotyping features were identified with variant ethambutol susceptibility. Among 77 isoniazid, rifampicin, streptomycin and ethambutol quadruple drug-resistant isolates, 89.6% carried embB mutations and 83.1% could be identified by detecting 10 embB mutations.ConclusionsOur results suggest embB mutations alone are not sufficient for the development of full resistance to ethambutol in M. tuberculosis and mutations other than embB are also needed. Our study confirms the importance of mutations at embB406 and embB497 as hotspots, in addition to embB306, for detecting ethambutol resistance. Ten selected mutations of embB, covered by a short PCR product, can be used as candidate markers for the prediction of quadruple resistance to isoniazid, rifampicin, streptomycin and ethambutol.

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

“…The level of embB406 mutations among EMB-resistant isolates was rather low, whereas mutations in codon embB497 were twice as frequent [11]. In our study, no mutation at embB codons 406 and 497 was found, which may be due to the limited sample size.…”

“…These genes are ubiquitous in mycobacteria and have no sequence similarity to any identified protein family in other bacteria. Consequently, the accumulation of mycolic acids due to a lack of arabinan receptors for mycolic acids results in cell death [9][10][11].…”

Ethambutol Resistance as Determined by Broth Dilution Method Correlates Better than Sequencing Results with embB Mutations in Multidrug-Resistant Mycobacterium tuberculosis Isolates

“…Ethambutol (EMB), one of the key first-line antimicrobial agents for the treatment of tuberculosis (4), plays an important role in the chemotherapy of drug-resistant TB, including MDR-TB (5). EMB inhibits arabinosyl transferases, encoded by the embCAB operon, thereby inhibiting biosynthesis of the cell well components arabinogalactan and lipoarabinomannan (6).…”

Detection of embB Gene Mutations in EMB-Resistant Mycobacterium tuberculosis Isolates From Isfahan Province by PCR-SSCP and Direct Sequencing

“…Plinke et al (24) show that with regard to the frequency of mutation in different codons, 68% of the mutations are in codon 306. Dawei Shi et al (29) reported that a significant number of the mutations in codons 406 and 497 occurred in the EMBr isolates without the occurrence of mutation in codon 306. They concluded that mutation in codons 406 and 497 are the signifiers of resistance to EMB.…”