Indan Journal of Medical Research Indan Journal of Medical Research Indan Journal of Medical Research Indan Journal of Medical Research
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Year : 2020  |  Volume : 151  |  Issue : 4  |  Page : 361-370

Genotype analysis of ofloxacin-resistant multidrug-resistant Mycobacterium tuberculosis isolates in a multicentered study from India

1 Division of Molecular Biology, ICMR-National AIDS Research Institute, Pune, Maharashtra, India
2 Department of Microbiology, Institute of Medical Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh, India
3 Department of Bacteriology, ICMR-National Institute for Research in Tuberculosis, Chennai, Tamil Nadu, India
4 Department of Immunology, ICMR-National Institute for Research in Tuberculosis, Chennai, Tamil Nadu, India

Correspondence Address:
Dr Vijay Nema
Division of Molecular Biology, ICMR-National AIDS Research Institute, 73 G MIDC, Bhosari, Pune 411 026, Maharashtra
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ijmr.IJMR_493_18

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Background & objectives: Drug resistance surveillance offers useful information on trends of drug resistance and the efficacy of control measures. Studies and reports of drug-resistant mutations and phenotypic assays thus become important. This study was conducted to investigate the molecular characteristics of ofloxacin (OFX)-resistant, multidrug-resistant tuberculosis (MDR-TB) isolates from different geographical regions of India and their association with strains of different genotypes. Further, the nitrate reductase assay (NRA) was tested against Mycobacteria Growth Indicator Tube (MGIT) for the determination of OFX resistance as an alternative and cost-effective method. Methods: A total of 116 Mycobacterium tuberculosis isolates were used to assess the mutations in the gyrA, gyrB genes and resistance levels to OFX. Mutational analysis in gyrA and gyrB genes and genotype analysis of M. tuberculosis isolates was done by gene-specific polymerase chain reaction (PCR) followed by DNA sequencing and spoligotyping, respectively. Results: Three (6.25%), 12 (44.44%) and 12 (29.27%) MDR-TB isolates from western, northern and southern India, respectively, were found to be OFX-resistant MDR-TB isolates. OFX resistance was observed to be significantly higher in MDR-TB cases for all study regions. Beijing genotypes from northern India were observed to be associated with OFX-resistant MDR-TB cases (P <0.05). Among 35 (30.15%) phenotypically OFX-resistant isolates, 22 (62.86%) had mutations in the gyrA gene and two (5.71%) isolates had mutations in the gyrB gene. Interpretation & conclusions: These results caution against the PCR-based prediction of OFX resistance patterns and highlight the need for searching other genetic loci for the detection of mutations conferring resistance to OFX in M. tuberculosis. Our study also showed the usefulness of NRA as an alternative method to detect OFX resistance.

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