Bactericidal activity of gatifloxacin (AM-1155) against Pseudomonas aeruginosa and Enterococcus faecalis in an in vitro bladder model simulating human urinary concentrations after oral administration

The bactericidal activity of gatifloxacin, a new 6-fluoro-8-methoxy quinolone, was determined in a dynamic in vitro model mimicking complicated lower urinary tract infection. Strains of Pseudomonas aeruginosa and Enterococcus faecalis with different susceptibility were exposed to changing gatifloxacin concentrations, simulating human urinary concentrations afer oral treatment with 200 mg twice daily for 3 consecutive days. Bacterial numbers of P. aeruginosa (minimal inhibitory concentrations, MIG: less than or equal to 32 mu g/ml) and of E. faecalis (MIC: 16 mu g/ml) were reduced to undetectable levels during exposure. For the strains with lower susceptibility, gatifloxacin showed bactericidal activity, but eradication was not complete. Thus, in a complicated urinary tract infection model, breakpoint MICs of gatifloxacin for uropathogenic organisms were presumed to range from 16 to 32 mu g/ml. At least 86% of recent clinical isolates of P. aeruginosa and E. faecalis were inhibited at its breakpoint MIG. These results suggest that gatifloxacin may be useful in the treatment of urinary tract infections. Copyright (C) 2000 S.Karger AG, Basel.