ABSTRACT
Introduction: Mycobacterium tuberculosis resists rifampicin (RIF) because of mutations in the rpoB (the p subunit of RNA polymerase) gene, mostly in the 81 bp region. \r\n', u'Objectives: Identify the frequency and characteristics relative to drug - resistant rpoB gene mutation in RIF - resistant M. tuberculosis strains. \r\n', u'Subjects and method: 40 M. tuberculosis strains including 11 RIF - sensitive strains and 29 RIF - resistant strains. Some bio molecular techniques were used such as extracting mycobacterial DNA, PCR, cloning, sequencing and analyzing mutation related RIF - resistance on rpoB gene. \r\n', u'Results: No mutation was found on the 81 bp region of rpoB gene of the RIF - sensitive M. tuberculosis strains. The rate of mutation on rpoB gene of 29 RIF - resistant M. tuberculosis strains is 96.6%. We found 12 mutation codon positions on the 81 bp region of the rpoB gene, and the mutation codon positions with high frequency were 531 (51.7%) and 526 (31%). The mutation position found in only one strain is codon 519 (3.4%) but not found in other reports. There are 15 types of drug resistant mutations in which TCG531 TCG is the most common with 50%. Multi - drug resistance was seen in mutable and none mutable cases, with all codon positions and mutable forms. \r\n', u'Conclusion: No mutation was found on the 81 bp region of the rpoB gene of RtF - sensitive M. tuberculosis strains. The rate of mutation on the rpoB gene of RIF - resistant M. tuberculosis strains is 96.6%. The new mutation position found is codon 519. The mutation on the rpoB gene does not determine the multi - drug resistance of M. tuberculosis. \r\n', u'