Molecular characterisation of drug resistance in <I>Mycobacterium tuberculosis</I> isolates from North India

Abstract

A tertiary care hospital in North India. To analyse the frequency of mutations associated with resistance to rifampicin (RMP), isoniazid (INH) and streptomycin (SM) in Mycobacterium tuberculosis. M. tuberculosis isolates from 171 pulmonary tuberculosis (TB) patients (newly diagnosed 102, 59.6%; retreated 69, 40.3%) were analysed. Drug susceptibility testing was performed using the proportion method and resistant isolates were characterised using the polymerase chain reaction, followed by restriction fragment length polymorphism and/or DNA sequencing, to screen for mutations in rpoB, katG, mabA-inhA and rpsL. Of the 171 isolates, 16.9% (29/171) were multidrug-resistant. Of the 102 newly diagnosed and 69 retreated cases, respectively 5.9% (6/102) and 33.3% (23/69) were multidrug-resistant. rpoB mutations were found in 100% (31/31) of the RMP-resistant isolates, the most common being S531L in 74.2% (23/31); katG315 mutations were found in 79.6% (35/44) of the INH-resistant isolates; however, no mabA-inhA (-15) mutation was found; rpsL mutations were found in 48.9% (24/49) of the SM-resistant isolates, and codon 43 mutation were found in 42.5% (21/49). This study characterises drug resistance-associated mutations in M. tuberculosis, information that could be used for the rapid screening of drug-resistant TB.