In vitro antibacterial activity of three new quinolone derivatives: rosoxacin, norfloxacin, pefloxacin.

The in vitro activities of rosoxacin, norfloxacin and pefloxacin against 480 bacterial strains were studied. MIC90s of norfloxacin and pefloxacin were less than or equal to 2 micrograms/ml for E. coli, Klebsiella sp., E. cloacae, Proteus sp. and Staphylococcus sp., less than or equal to 8 micrograms/ml for C. freundii, Providencia sp., S. faecalis, and non fermentative Gram-negative bacteria, while they were of 32 micrograms/ml for S. marcescens. Rosoxacin exhibited a lower activity with MIC90s 2 to 16 fold higher against Enterobacteriaceae and P. aeruginosa. Ninety per cent of isolates resistant to nalidixic-acid appeared susceptible to norfloxacin and pefloxacin with MIC less than or equal to 16 micrograms/ml.