Early detection of multi-drug resistance and common mutations in Mycobacterium tuberculosis isolates from Delhi using GenoType MTBDRplus assay

Purpose: There is scarcity of prevalence data of multi-drug-resistant tuberculosis (MDR-TB) data and common mutations responsible in North India. This study aimed to detect MDR-TB among MDR-TB suspects from Delhi and mutation patterns using GenoType MTBDRplus assay. Materials and Methods: All MDR suspects in five districts of New Delhi were referred to the laboratory from 1 st October 2011 to 31 st December 2012 as per criterion defined by Programmatic Management of Drug Resistant Tuberculosis (PMDT). GenoType MTBDRplus assay was performed on 2182 samples or cultures and mutations in the rpoB gene for rifampicin (RIF) and katG and inhA genes for isoniazid (INH) were analyzed. Results: A total of 366 (16.8%) MDR-TB cases were diagnosed. MDR rate was found to be 32%, 16.6% and 10.2% during criterion A, B and C respectively. The most common mutation detected for RIF was S531L (59.0%) and for INH was S315T1 (88.3%). Mutations S531L and S315T1 occurred significantly higher in MDR strains as compared to RIF mono-resistant and INH mono-resistant strains, respectively. Average laboratory turn-around time (TAT) for dispatch of result to districts for test conducted on samples was 4.4 days. Conclusion: GenoType MTBDRplus is a useful assay for rapid detection of MDR-TB. The common mutations for RIF and INH were similar to those seen in other regions. However, mutations determining MDR strains and mono-resistant strains differed significantly for both RIF and INH.