The In-vitro Activities of Enoxacin and Ofloxacin Compared with That of Ciprofloxacin

The in-vitro activities of enoxacin and ofloxacin were compared with that of the other new 4-quinolone, ciprofloxacin. All three compounds were highly active against Enterobacteriaceae, Haemophilus influenzae and Neisseria gonorrhoeae (MICs mostly less than 1 mg/l). The other Gram-negative aerobes tested were in general less susceptible, though for Acinetobacter and Pseudomonas species (including aeruginosa) MICs seldom exceeded 8 mg/l. Ofloxacin and ciprofloxacin were more active against Gardnerella vaginalis (MICs 0.5-2 mg/l) than was enoxacin (MICs 8-32 mg/l). Staphylococci were susceptible to ofloxacin (MICs 0.12-1 mg/l) and enoxacin (MICs 0.5-2 mg/l) as well as to ciprofloxacin. Streptococci also were mostly sensitive to the compounds though the MICs of enoxacin (4-64 mg/l) were noticeably higher than those of ofloxacin (1-4 mg/l). Anaerobes were in general susceptible though, as with streptococci, ofloxacin, with activity similar to that of ciprofloxacin, was more active than enoxacin. Variants of Enterobacteriaceae with reduced susceptibility were readily selected in the laboratory with either enoxacin or ofloxacin as the selective agent. The MICs of all the 4-quinolones were usually increased four- to 16-fold for these strains; they could therefore be regarded as remaining susceptible to the newer compounds.