Comparative in vitro activity of norfloxacin against resistant Neisseria gonorrhoeae.

The in vitro activity of seven antibiotics against 52 isolates of Neisseria gonorrhoeae was determined. Against penicillinase-producing Neisseria gonorrhoeae, ceftriaxone was the most active agent (MIC90 0.015 micrograms/ml), followed by ceftizoxime and norfloxacin (MIC90 0.03-0.125 micrograms/ml). Against spectinomycin-resistant Neisseria gonorrhoeae, the most active agents were ceftizoxime, ceftriaxone and norfloxacin (MIC90 0.015-0.125 micrograms/ml). Ceftizoxime, ceftriaxone and norfloxacin were also the most active agents against tetracycline-resistant Neisseria gonorrhoeae (MIC90 0.06-0.125 micrograms/ml). Overall, the rank order of activity from the most to the least active agent was as follows: ceftizoxime (MIC90 0.015 micrograms/ml); ceftriaxone (MIC90 0.06 micrograms/ml); norfloxacin (MIC90 0.125 micrograms/ml); cefoxitin (MIC90 2 micrograms/ml); tetracycline (MIC90 8 micrograms/ml); penicillin (MIC90 greater than 8 micrograms/ml); and spectinomycin (MIC90 greater than 128 micrograms/ml).