[Effect ofloxacin on Haemophilus influenza, Streptococcus pneumoniae and Neisseria meningitidis. Comparison with similar molecules].

The in vitro activities of the new quinolone derivatives ofloxacin, ciprofloxacin, norfloxacin, and pefloxacin against strains of Haemophilus influenzae, Streptococcus pneumoniae and Neisseria meningitidis were compared to that of nalidixic acid. Determination of minimal inhibitory concentrations (MICs) was done by agar dilution tests. The new drugs were more active than nalidixic acid. N. meningitidis and H. influenzae (regardless of beta-lactamase production) were highly susceptible. All H. influenzae strains were inhibited by less than or equal to 0.12 mg/l; mode MICs were 0.03 mg/l for norfloxacin and pefloxacin, and 0.50 mg/l for nalidixic acid. All N. meningitidis strains were inhibited by 0.06 mg/l and mode MICs of the new drugs were less than or equal to 0.03 mg/l. Mode MICs for S. pneumoniae were 4 mg/l for norfloxacin and pefloxacin (range 1-16 and 2-8 mg/l respectively) and 1 mg/l for ofloxacin (range 1-4 mg/l). Ofloxacin exhibited a bactericidal activity on H. influenzae (range MBC 0.06-0.50 mg/l; mode MBC: 0.06 mg/l).