Mutation in katG315 is, possibly, a good prognostic marker for treatment with second-line drugs in multi-drug resistant tuberculosis: a preliminary study.

The aim of this study was to explore baseline data, laboratory and molecular analyses to determine if any could serve as potential prognostic marker(s) for treatment response to second line tuberculosis regimens. Of a total number of 50 multi-drug resistant tuberculosis (MDR-TB) patients starting second-line drug MDR-TB treatment in Iraq, only 21 showed treatment adherence and thus, included in this study. Response to treatment was monitored for 11 months by sputum microscopy and culture. We explored baseline data, laboratory and molecular analyses to determine if any could serve as potential prognostic marker(s) for treatment response. Highly significant association (P = 0.019) was detected between mutations in katG315 codon and good response to second-line anti-TB drugs. Spoligotyping and mycobacterial interspersed repetitive unit variable number tandem repeat confirmed that katG315-mutatnt isolates were genotypically unrelated. The katG315 mutation is a potential prognostic marker for treatment response to second-line anti-tuberculosis drugs. One possible explanation of our results is that the katG315-mutants are sensitive to bacterial killing by "oxidative killing.".