Mutations in the gyrA and parC genes and in vitro activities of fluoroquinolones in 91 clinical isolates of Neisseria gonorrhoeae in Japan

BACKGROUND AND OBJECTIVES: Fluoroquinolone resistance in Neisseria gonorrhoeae has been associated with alternations in the quinolone-resistance determining regions in the gyrA and parC genes. GOAL: The goal of this study was to investigate the correlation between fluoroquinolone minimum inhibitory concentrations (MICs) and mutations in the gyrA and parC genes of 91 N. gonorrhoeae clinical isolates from Japan. STUDY DESIGN: The MICs of fluoroquinolones ciprofloxacin, levofloxacin, and gatifloxacin for 91 clinical isolates from male gonococcal urethritis in Hyogo or Osaka, Japan, were measured, and the gyrA and parC genes of these isolates were sequenced. RESULTS: Among 91 isolates tested, over 70% isolates were resistant to ciprofloxacin. We found that 4 mutations (Ser-91-Phe, Ser-91-Ile, Asp-95-Gly in gyrA, and Ser-88-Pro in parC) had significant correlation to MICs of fluoroquinolone (ciprofloxacin, levofloxacin, and gatifloxacin). CONCLUSION: Some mutations in QRDR had a significant relationship to the fluoroquinolone resistance of N. gonorrhoeae clinical isolates from Japan.