LEVOFLOXACIN IN-VITRO ACTIVITY - RESULTS FROM AN INTERNATIONAL COMPARATIVE-STUDY WITH OFLOXACIN AND CIPROFLOXACIN

Levofloxacin, the S-(-)-isomer of ofloxacin, was compared to ofloxacin and ciprofloxacin against > 6000 recent clinical isolates of Gram-pos itive and Gram-negative bacteria from six different countries. This in ternational multicenter study demonstrated a high level of antibacteri al activity of levofloxacin against all the members of Enterobacteriac eae [minimum inhibitory concentration (MIC)50s, less-than-or-equal-to 0.03 to 0.12 mg/L] except Providencia rettgeri (MIC50, 2 mg/L), and Pr ovidencia stuartii (MIC50, 1 mg/L). Oxacillin-susceptible staphylococc i (MIC50s, 0.12 to 0.25 mg/L), enterococci (MIC50s, 0.5 to 2 mg/L), an d streptococci (MIC50s, 0.5 mg/L) were also susceptible to levofloxaci n, but most isolates of oxacillin-resistant staphylococci had MICs of greater-than-or-equal-to 4 mg/L. Levofloxacin was also active against non-enteric Gram-negative bacilli, including Acinetobacter species (MI C50s, less-than-or-equal-to 0.03 to 1 mg/L), Pseudomonas species (MIC5 0s, 0.5 to 1 mg/L) and Xanthomonas maltophilia (MIC50, 0.5 mg/L). Over all, levofloxacin inhibited 50% and 90% of all the tested strains at t he concentrations of 0.12 and 4 mg/L, respectively. The activity of le vofloxacin was generally two-fold greater than ofloxacin and equal to or slightly less potent than ciprofloxacin.