Identification of mutations in the rpoB encoding the RNA polymerase beta subunit in rifampicine-resistant Mycobacterium tuberculosis strains from Iran

The aim of this study was to investigate the frequency, location and type of rpoB mutations in Mycobacterium tuberculosis isolated from patients in Iran. 91 sputum were collected from suspected tuberculosis patients, 34 Rif-r isolates (87%) were identified as M. tuberculosis. Polymerase chain reaction (PCR) amplification and DNA sequencing methods were performed. 411 bp fragments of rpoB gene were sequenced and mutations in 81 bp regions were analyzed. 60 mutations and 13 micro deletions were identified in 29 RIF-r MBT (85%). Among 60 mutations, 6 silent and 54 missense were identified. Missense mutations produced 23 types of amino acid substitutions. In 5 RIF-r MBT 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 from Iranian strains were in codons 523 and 526. Five alleles in codon 526 and 3 alleles in triplets in each codons 507, 508, 513 were found. 6 (19%) strains harboured single mutations 6 (18%) placed in codons 526, 510 while the rest of isolates 23 (69%) had multiple mutations: Double 11 (34%), triple 7 (22%), and quartile mutations 1 (3%) and 4 (12%) of strains harboured 5 mutations respectively.