Exploring quinolone resistance-determining region in Neisseria gonorrhoeae isolates from across India

BACKGROUND & OBJECTIVES: Antimicrobial resistance in Neisseria gonorrhoeae, the causative agent of gonorrhoea, is a subject of worldwide attention. The present study was undertaken to examine the rates of ciprofloxacin resistance, to correlate mutations in gyrA and parC genes with the level of resistance and to look for a variation in mutation pattern, if any, in isolates from across the country. METHODS: A total of 113 isolates of N. gonorrhoeae collected from sexually transmitted infection patients in six centres during November 2010 to October 2013 were investigated. Minimum inhibitory concentration (MIC) determination was done by E-test and results interpreted as per Calibrated Dichotomous Sensitivity criteria. DNA sequence analysis of gyrA and parC genes was done. RESULTS: Of the 113 isolates, only three (2.6%) were susceptible whereas eight (7.07%) were less susceptible, 32 [28.3%, 95% confidence interval (CI): 20.4-37.6%] resistant (MIC 1-3 µg/ml) and 70 (61.9%, 95% CI: 52.2-70.7%) exhibited high-level resistance (HLR) (MIC ≥4 µg/ml) to ciprofloxacin. A S91F substitution in gyrA gene was demonstrated in all ciprofloxacin non-susceptible isolates. All resistant and HLR isolates had a double mutation in gyrA gene. However, only 5.7 per cent of HLR isolates showed double mutations in parC gene. One isolate (MIC 32 µg/ml) had a previously undescribed G85D substitution in the parC gene. INTERPRETATION & CONCLUSIONS: A S91F substitution in gyrA gene was seen in all non-susceptible isolates of N. gonorrhoeae. It may be used as a marker for ciprofloxacin resistance for molecular surveillance approaches to complement the culture-based methods.