Molecular characterisation of mutations associated with resistance to first- and second-line drugs among Indonesian patients with tuberculosis

OBJECTIVES: This study aimed to determine molecular characteristics of rpoB, katG, rrs, and gyrA genes in Mycobacterium tuberculosis isolated from a cohort of Indonesian patients with tuberculosis. METHODS: Fifty isolates of M. tuberculosis were analysed by testing (DST) for susceptibility to first- and second-line drugs using the proportional method in a liquid medium. The genomic material was extracted to perform multiplex polymerase chain reaction (PCR) for identification and gene sequencing of rpoB, katG, rrs, and gyrA. RESULTS: Approximately 80% (40/50) of the rpoB mutations that were detected outside the hot-spot region (S450L, H445D, D435V, S441L, I491F, and Q432P) conferred rifampicin-resistance on M. tuberculosis. Approximately 11.42% (4/35) of isolates with S315T mutation in katG led to rifampicin-resistance instead of isoniazid-resistance. The mutation in katG gene was found at various locations (P280P, G279R, E340Q, T271I, E340*stop codon, R373G, and S315N). Streptomycin-resistance was detected in 42% (21/50) of the strains, but only two strains had rrs gene mutations (G878A and/or S514R). Approximately 14% (7/50) of M. tuberculosis isolates were kanamycin- and capreomycin-resistant but did not harbour mutations in the rrs gene, while 80% (40/50) of the strains had mutations in the quinolone-resistance determining region (QRDR) of the gyrA gene (S95T, D94V, A90V, and S91P) including the pan-susceptible strain. CONCLUSIONS: Of the 50 strains analysed, most of the mutations in the rpoB gene associated with rifampicin-resistance were also detected in the katG and gyrA genes. Molecular characterisation using DNA sequencing techniques is a highly sensitive approach for detecting mutations.