title: Molecular characterization of multidrug-resistant isolates of Mycobacterium tuberculosis from patients in North India.
abstract: The World Health Organization has identified India as a major hot-spot region for Mycobacterium tuberculosis infection. We have characterized the sequences of the loci associated with multidrug resistance in 126 clinical isolates of M. tuberculosis from India to identify the respective mutations. The loci selected were rpoB (rifampin), katG and the ribosomal binding site of inhA (isoniazid), gyrA and gyrB (ofloxacin), and rpsL and rrs (streptomycin). We found known as well as novel mutations at these loci. Few of the mutations at the rpoB locus could be correlated with the drug resistance levels exhibited by the M. tuberculosis isolates and occurred with frequencies different from those reported earlier. Missense mutations at codons 526 to 531 seemed to be crucial in conferring a high degree of resistance to rifampin. We identified a common Arg463Leu substitution in the katG locus and certain novel insertions and deletions. Mutations were also mapped in the ribosomal binding site of the inhA gene. A Ser95Thr substitution in the gyrA locus was the most common mutation observed in ofloxacin-resistant isolates. A few isolates showed other mutations in this locus. Seven streptomycin-resistant isolates had a silent mutation at the lysine residue at position 121. While certain mutations are widely present, pointing to the magnitude of the polymorphisms at these loci, others are not common, suggesting diversity in the multidrug-resistant M. tuberculosis strains prevalent in this region. Our results additionally have implications for the development of methods for multidrug resistance detection and are also relevant in the shaping of future clinical treatment regimens and drug design strategies.
authors.affiliation: Centre for DNA Fingerprinting and Diagnostics, Hyderabad 500076 , India.
authors.forename: Noman
authors.initials: N
authors.lastname: Siddiqi
authors.forename: Mohammed
authors.initials: M
authors.lastname: Shamim
authors.forename: Seema
authors.initials: S
authors.lastname: Hussain
authors.forename: Rakesh Kumar
authors.initials: RK
authors.lastname: Choudhary
authors.forename: Niyaz
authors.initials: N
authors.lastname: Ahmed
authors.lastname: Prachee
authors.forename: Sharmistha
authors.initials: S
authors.lastname: Banerjee
authors.forename: G R
authors.initials: GR
authors.lastname: Savithri
authors.forename: Mahfooz
authors.initials: M
authors.lastname: Alam
authors.forename: Niteen
authors.initials: N
authors.lastname: Pathak
authors.forename: Amol
authors.initials: A
authors.lastname: Amin
authors.forename: Mohammed
authors.initials: M
authors.lastname: Hanief
authors.forename: V M
authors.initials: VM
authors.lastname: Katoch
authors.forename: S K
authors.initials: SK
authors.lastname: Sharma
authors.forename: Seyed E
authors.initials: SE
authors.lastname: Hasnain
mesh_terms: D001483:Base Sequence; D027081:DNA Gyrase / Q000235:genetics; D004269:DNA, Bacterial / Q000032:analysis; D012321:DNA-Directed RNA Polymerases; D015195:Drug Design; D018432:Drug Resistance, Multiple / Q000235:genetics*; D005798:Genes, Bacterial; D006801:Humans; D007194:India; D008969:Molecular Sequence Data; D009154:Mutation; D009169:Mycobacterium tuberculosis / Q000235:genetics*; D010940:Plant Proteins / Q000235:genetics*
chemical_list: D004269:DNA, Bacterial; D010940:Plant Proteins; C101305:RpoB protein, Oryza sativa; D012321:DNA-Directed RNA Polymerases; D027081:DNA Gyrase