Antimicrobial resistance of Neisseria gonorrhoeae and high prevalence of ciprofloxacin-resistant isolates in Japan, 1993 to 1998.

To assess the antimicrobial resistance of Neisseria gonorrhoeae isolated from 1993 through 1998 in Japan, susceptibility testing was conducted on 502 isolates. Selected isolates were characterized by auxotype and analysis for mutations within the quinolone resistance-determining region (QRDR) in the gyrA and parC genes, which confer fluoroquinolone resistance on the organism. Plasmid-mediated penicillin resistance (penicillinase-producing N. gonorrhoeae) decreased significantly from 1993-1994 (7.9%) to 1997-1998 (2.0%). Chromosomally mediated penicillin resistance decreased from 1993-1994 (12.6%) to 1995-1996 (1.9%) and then increased in 1997-1998 (10.7%). Chromosomally mediated tetracycline resistance decreased from 1993-1994 (3.3%) to 1997-1998 (2.0%), and no plasmid-mediated high-level tetracycline resistance was found. Isolates with ciprofloxacin resistance (MIC >/= 1 microg/ml) increased significantly from 1993-1994 (6.6%) to 1997-1998 (24.4%). The proline-requiring isolates were less susceptible to ciprofloxacin than the prototrophic or arginine-requiring isolates. Ciprofloxacin-resistant isolates contained three or four amino acid substitutions within the QRDR in the GyrA and ParC proteins.