Comparative in vitro activity of RO 23-6240 (fleroxacin), a new 4-quinolone derivative.

The in vitro activity of RO 23-6240 was compared with that of norfloxacin, ofloxacin and ciprofloxacin as well as four other antimicrobial agents against 345 recent clinical isolates. The MICs of RO 23-6240 against Enterobacteriaceae and Acinetobacter anitratum was less than or equal to 0.5 mg/l. At the same concentration of the compound 90% of staphylococci were inhibited. Against Enterococcus faecalis and Pseudomonas aeruginosa RO 23-6240 proved less active, having MIC90 values of 4.0 mg/l and 8.0 mg/l, respectively. Enterobacteriaceae and staphylococci strains that were resistant to piperacillin, cefotaxime or tobramycin were susceptible to the compound. In general the activity of RO 23-6240 was comparable to those of norfloxacin and ofloxacin, but less than that of ciprofloxacin.