In vitro activity of six quinolone derivatives against Neisseria gonorrhoeae.

The in vitro activities of six quinolone derivatives, rosoxacin, pefloxacin, ofloxacin, ciprofloxacin, A-56619 and A-56620, were compared with those of penicillin, cefotaxime, spectinomycin, chloramphenicol, tetracycline and erythromycin against 50 nonpenicillinase-producing and 15 penicillinase-producing Neisseria gonorrhoeae strains. Ciprofloxacin was the most active compound in vitro (MIC50, 0.004 mg/l) followed by ofloxacin and A-56620 (MIC50, 0.008 mg/l), A-56619 and cefotaxime (MIC50, 0.016 mg/l). The six quinolones are highly active against all the strains tested but 2, with decreased sensitivity.