The in-vitro activity of CI-934 compared with that of other new 4-quinolones and nalidixic acid.

The in-vitro activity of CI-934, a new 4-quinolone compound, was compared with that of the other new 4-quinolones, enoxacin and ciprofloxacin, and also with that of nalidixic acid. CI-934 was more active than any of the other 4-quinolones tested against Gram-positive aerobic organisms including Staphylococcus aureus (MICs 0.06-0.25 mg/l), beta-haemolytic streptococci (MICs 0.12-0.5 mg/l), Streptococcus pneumoniae (MICs 0.25-0.5 ml/l), viridans streptococci (MICs 0.06-0.5 mg/l) and most enterococci (MICs 0.12-0.5 mg/l), although some ampicillin-resistant isolates of Str. faecium were slightly less susceptible (MICs 2 mg/l). All three of the newer 4-quinolones tested were highly active against Enterobacteriaceae, Aeromonas sp., Haemophilus influenzae and Neisseria gonorrhoeae (MICs mostly less than 1 mg/l). The other Gram-negative aerobes tested were in general somewhat less susceptible, although for Acinetobacter and Pseudomonas aeruginosa MICs seldom exceeded 8 mg/l. CI-934 was more active than enoxacin against Gardnerella vaginalis (MICs 1-8 mg/l) although it was a little less active than ciprofloxacin. Bacteroides species (including about half of the fragilis group) were susceptible to CI-934 (MICs mostly 1-8 mg/l): ciprofloxacin had similar activity but enoxacin was less active. Other anaerobes tested were mostly highly susceptible to CI-934 (MICs 1 mg/l or less) but were somewhat less susceptible to enoxacin and ciprofloxacin.