Frequency and molecular characterization of rifampicin-resistance in rpoB region of multiple drug resistance (MDR) isolates from tuberculosis patients in southern endemic region of Iran

The aim of this study was to investigate the frequency, location and type of rpoB gene mutations in Mycobacterium tuberculosis (MTB) collected from patients in the southern endemic region of Iran. Drug susceptibility testing was determined by using the BACTEC system and the center for diseases controls (CDC) standard conventional proportional method. In 29 rifampicin-resistant MTB (85%) isolates, 60 mutations and 13 micro-deletions were identified. Missense mutations produced 23 types of amino acid substitutions. In five rifampicin-resistant MTB isolates (15%) no mutations were found in the core region of the rpoB gene. All silent mutations were localized in codon 507. Most frequent mutations detected in Iranian strains, were found in codons 523 and 526. Five alleles in codon 526 and three alleles occurring in triplets in each of the codons 507, 508, 513 were also found. Thus in Iran the highest frequency of common mutations shared between primary and secondary infections was found to occur in codons 523 and 526.