Association among the Rv2629 gene, rpoB gene, RFP resistance and Beijing genotype in Mycobacterium tuberculosis clinical isolates.

Abstract

Rifampin (RFP) is a major first-line anti-tuberculosis drug. The molecular assay currently used is the detection of rpoB gene mutations in Mycobacteriumtuberculosis. Recently, the Rv2629 191C allele was found to have a correlation with RFP resistance, and might become a valuable marker for the detection of RFP resistance or the Beijing genotype. We studied the association among the Rv2629gene, rpoB gene, RFP resistance and Beijing genotype in 69 M. tuberculosis clinical isolates using DNA sequencing, conventional drug susceptibility and spoligotyping. The 191C allele was present in 92.8% (64/69) isolates. Of 29 RFP-sensitive strains, none exhibited any mutations in rpoB genes, only one strain (3.4%) was found to carry the 191A allele and 28 strains (96.6%) had the 191C alleles. Of 40 RFP-resistant strains, 30 (75%) strains had rpoB gene mutations, only 4 strains (10%) carried 191A alleles, and 36 strains (90%) exhibited 191C alleles. The 191C allele was also present in INH-sensitive, SM-sensitive or EMB-sensitive isolates. Spoligotyping analysis showed 8 distinct spoligotyping patterns. 81.1% (30/37) strains were divided into one big cluster, which had a characteristic of the Beijing genotype. Rv2629 191C allele was present in 93.3% (28/30) Beijing genotype strains, but also in non-Beijing genotype strains. These results indicate that high association is present between the ropB gene and RFP resistance. No association is present between the Rv2629 191C allele and RFP resistance, or between the Beijing genotype and RFP resistance. Key words: Mycobacterium tuberculosis, Rv2629, rpoB, rifampin resistance, spoligotyping.