title: 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.
authors: Department of Biotechnology, New Drug Discovery Research, Ranbaxy Research Laboratories, Gurgaon, India.
authors: Alka
authors: A
authors: Khanna
authors: V Samuel
authors: VS
authors: Raj
authors: Bansidhar
authors: B
authors: Tarai
authors: Ruchi
authors: R
authors: Sood
authors: Pawan Kumar
authors: PK
authors: Pareek
authors: Dilip J
authors: DJ
authors: Upadhyay
authors: Pawan
authors: P
authors: Sharma
authors: Ashok
authors: A
authors: Rattan
authors: Kulvinder Singh
authors: KS
authors: Saini
authors: Harpal
authors: H
authors: Singh
mesh_terms: D000583:Amikacin / Q000494:pharmacology; D000995:Antitubercular Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics; D002207:Capreomycin / Q000494:pharmacology; D027081:DNA Gyrase / Q000737:chemistry / Q000235:genetics; D004252:DNA Mutational Analysis; D012321:DNA-Directed RNA Polymerases; D054908:Extensively Drug-Resistant Tuberculosis / Q000382:microbiology*; D024841:Fluoroquinolones / Q000494:pharmacology; D007194:India; D007538:Isoniazid / Q000494:pharmacology; D007612:Kanamycin / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D009154:Mutation; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000235:genetics* / Q000472:pathogenicity; D017354:Point Mutation / Q000235:genetics; D016133:Polymerase Chain Reaction; D012293:Rifampin / Q000494:pharmacology
chemical_list: D000995:Antitubercular Agents; D001426:Bacterial Proteins; D024841:Fluoroquinolones; C505805:rpoB protein, Mycobacterium tuberculosis; D002207:Capreomycin; D007612:Kanamycin; D000583:Amikacin; D012321:DNA-Directed RNA Polymerases; D027081:DNA Gyrase; D007538:Isoniazid; D012293:Rifampin