Mutations of rpob Gene Associated with Rifampin Resistance among Mycobacterium Tuberculosis Isolated in Tuberculosis Regional Reference Laboratory in Northeast of Iran during 2015-2016

Abstract

BACKGROUND: Drug resistance is a leading concern in controlof TB. Resistance against rifampin as one of the most importantdrugs in the treatment of Mycobacterium tuberculosis is causedby mutations in the 81-base pair region of the rpoB gene encodingthe β-subunit of RNA polymerase. This study aimed to characterizethe mutations in the rpoB gene associated with rifampin resistanceamong M. tuberculosis.METHODS: This study was conducted on referred samples ofpatients who did not respond to anti-TB treatment, in TuberculosisRegional Reference Laboratory at Shariati Hospital. Drugsusceptibility of M. tuberculosis isolates was surveyed using aproportional method on LJ medium. The isolates with resistant torifampin were reconfirmed and then the rpoB gene was amplifiedand sequenced.RESULTS: Among 27 resistant cases, 8, 11 and 8 people were fromIran, Afghanistan, and Turkmenistan, respectively. In 26 out of 27isolates, rpoB gene mutations were observed. The most prevalentmutations belonged to the codon 53. The most prevalentmutations belonged to the TCG (Ser) 531TTG (leu) withprevalence 51.8% (n=14), and GAC (Asp)516TAC (Tyr), CAC(His) 526GAC (Asp) and CAC (His) 526TAC(Tyr) mutationswith prevalence 14.8%(n=4). Twenty-three isolates had just onemutation.CONCLUSION: The use of rpoB gene sequencing led to the lackof the need for growth of the organism in the culture medium, thedirect use of clinical samples, reduction of biological risks and adetection about 96.3% of MDR TB cases lowering the cost of thetreatment.