Mutational profile of gyrA and gyrB genes associated with fluoroquinolones (FQs) resistance among drug resistant tuberculosis patients: an observational study

Abstract

<b>Background:</b> Drug resistant tuberculosis is a serious public health problem in India. Due to inappropriate use, resistance to FQs has increased, which is a major threat to control TB worldwide. FQ resistance is caused by mutation in gyrA and gyrB genes of Mycobacterium tuberculosis. This study was aimed to detect mutations in gyrA and gyrB genes associated with FQ resistance among drug resistant tuberculosis (DR-TB) patients. <b>Method:</b> This was a cross sectional, observational study in which1400 presumptive DR-TB caseswere screened by GeneExpert and first line-Line probe assay (FL-LPA). Patients who were found to have any drug resistance were subjected to second-line LPA (SL-LPA) to detect FQ resistance. We further collected data on genetic mutations responsible for FQ resistance. <b>Result:</b> Of 1400 cases, DR-TB was found in 245(17.5%) patients, out of which 32(2.2%),115(8.2%), 98(7.0%) were resistant to rifampicin, isoniazid and to both isoniazid and rifampicin, respectively. FQ resistance was observed in 97(39.6%) of total DR-TB cases. 96 isolates had mutations in gyrA and only 1 in gyrB gene. Most common mutation was MUT3C (54.16%) followed by MUT1 (20.83%). About half of the patients had prior FQ exposure history. <b>Conclusion:</b> Early detection of mutations in FQ resistant patients helps in selection of adequate drug regimen. Increased FQ resistance also indicates inappropriate use of FQs, so judicious use of FQs should be encouraged.