Emergence and Molecular Characterization of Extensively Drug-Resistant Mycobacterium tuberculosis Clinical Isolates from the Delhi Region in India

Abstract

We screened 194 Mycobacterium tuberculosis strains isolated from tuberculosis (TB) patients in Delhi and neighboring regions in India to identify the prevalence of extensive drug resistance (XDR) in clinical isolates. Among these, 104 isolates were found to be multidrug resistant (MDR), and 6 were identified as XDR isolates, which was later confirmed by antimicrobial susceptibility testing against the respective drug screening panel. Genotyping was carried out by amplifying and sequencing the following genes: rpoB (rifampin), katG (isoniazid), gyrA (fluoroquinolones), and rrs (amikacin, kanamycin, and capreomycin). Our analyses indicated that mutations at the hot spots of these genes were positively correlated with drug resistance in clinical isolates. The key mutation observed for rpoB was in the codon for amino acid position 531 (S531L), and other mutations were seen in the hot spot, including those encoding Q510P, L511H, D516V, and H526Y mutations. We identified S315T and R463L substitutions encoded in the katG locus. An S95T substitution encoded in the gyrA locus was the most common mutation observed in fluoroquinolone-resistant isolates. In addition, we saw D94G and D94N mutations encoded in the QRDR region. The 16S rRNA (rrs) gene encoded mainly the A1401G mutation and an additional mutation, G1484T, resulting in ribosomal modifications. Taken together, the data in this report clearly establish the presence of phenotypically distinct XDR strains in India by molecular profiling and further identify specific mutational hot spots within key genes of XDR-TB strains.

Characterization of Mutations Conferring Extensive Drug Resistance to Mycobacterium tuberculosis Isolates in Pakistan

“…Screening of the rrs gene for detection of resistance to AMK, KAN, and CAP revealed the A1401G mutation to be the most common and present mutation in 66% of XDR isolates, consistent with reports from India and China (4,34,47). All isolates with an rrs nt 1401 mutation were KAN and AMK resistant, but 51.5% were CAP susceptible.…”

Prevalence of drug-resistant pulmonary tuberculosis in India: systematic review and meta-analysis

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Emergence of Potential Superbug Mycobacterium Tuberculosis , Lessons from New Delhi Mutant-1 Bacterial Strains

“…Several studies including our group have reported incidences of Rifampin resistant Mycobacterium in clinical isolates. (32)(33)(34)(35) Interestingly, the 96 % of the Mycobacterium tuberculosis clinical isolates screened were found to have in 81 bp core region of rpoB gene, which encodes for the beta subunit of RNA polymerase. (36) Missense mutations in codons 513, 526, or 531 resulted in high level Rifampin resistance; whereas amino acid changes at position 514 or 533 usually resulted in low levels of Rifampin resistance.…”