Geographical profile of rpoB mutations of Mycobacterium tuberculosis clinical isolates and their correlation with the therapeutic outcome

Abstract

Present study aims to study the geographical profile of rpoB mutations of Mycobacterium tuberculosis
clinical isolates and their correlation with the therapeutic outcome. All the isolates were tested for drug
susceptibility testing on Lowenstein-Jensen medium and PCR and DNA sequencing for rpoB gene
mutations. Fifty two out of 101(52%) isolates were pan susceptible of which 79% were associated with
cure. Thirty five isolates (35%) showed a combined resistance to isoniazid and rifampicin, out of which
63% were associated with treatment failure. Majority (94%) of the isolates from cured patients showed
wild type of rpoB sequence; where as 77% of patients who failed the treatment were associated with
mutations. Twenty eight out of 38(74%), rifampicin resistant isolates showed commonly occurring
mutations such as 531, 526 and 516. Multiple silent mutations between the codons 145 - 184 (out side
the hot spot region) are being reported for the first time in this study. Information on the geographical
profile of rpoB mutations in M. tuberculosis may therefore facilitate for an improved diagnosis of
rifampicin resistance, by increasing the efficacy of the gene sequencing based tests.