A Multicenter Study on the Comparative In Vitro Activity of Fleroxacin and Three Other Quinolones: An Interim Report from 27 Centers

Abstract

A multicenter study was designed to compare the in vitro activity of fleroxacin to that of three other oral quinolones (ciprofloxacin, ofloxacin, and lomefloxacin) against fresh clinical bacterial isolates in hospital or medical center laboratories throughout the United States. Each of the 50 centers was asked to test 500 gram-negative and gram-positive strains using the MicroScan (Baxter) microtiter system. This report includes the results of the study, begun in October 1990, on 12,013 isolates tested in 27 centers. Susceptibility was based on minimum inhibitory concentration (MIC) interpretive criteria from the National Committee for Clinical Laboratory Standards guidelines or published literature. Fleroxacin and the three other quinolones were all active against Enterobacteriaceae, with 95-97% of the strains susceptible. Against other aerobic gram-negative bacilli, 79-83% of the strains were susceptible to fleroxacin, ciprofloxacin, and ofloxacin, and 75% were susceptible to lomefloxacin. With regard to the gram-positive isolates, 79% were susceptible to ofloxacin, 74% to ciprofloxacin, and 52% to fleroxacin and lomefloxacin. The susceptibility data were further delineated for the various species in each of the three major bacterial groups. All four quinolones were highly active against Enterobacteriaceae and were moderate to excellent in activity against other aerobic gram-negative organisms. Activity against oxacillin-susceptible staphylococci was also excellent; however, all four agents were generally much less active against oxacillin-resistant strains. Ofloxacin and ciprofloxacin were clearly superior to fleroxacin and lomefloxacin against streptococci and enterococci.