Fluoroquinolones are one of the new classes of antimicrobial agents that are being increasingly used against tuberculosis, the most important ones are ciprofloxacin, ofloxacin, and the new generations drugs-gatifloxacin and moxifloxacin. The clinical isolates of Mycobacterium tuberculosis (47 ofloxacin- susceptible and 71 ofloxacin-resistant) strains obtained from individual patients from various parts of India were analyzed for gyr A mutation in quinolone resistant determining region (QRDR). Most of the mutations were seen clustered in the codons 90, 94 and 95, which is a hot spot region of...