RO23-6240, a new orally absorbed quinolone: in vitro comparison with other broad-spectrum oral antimicrobial agents and imipenem.

A total of 626 clinical isolates were tested for their susceptibility to RO23-6240 and other broad-spectrum antimicrobial agents. RO23-6240 showed good activity against strains of Enterobacteriaceae, Acinetobacter, and P. aeruginosa. RO23-6240 MIC90s ranged from 0.032 to 4 micrograms/ml for these strains. RO23-6240 also showed good activity against staphylococci, both methicillin-susceptible and -resistant strains. The activity in vitro of RO23-6240 was comparable with that of norfloxacin and ofloxacin, and more active than imipenem, trimethoprim-sulfamethoxazole, cefaclor, and amoxycillin/clavulanate potassium. As with the other quinolones tested, increases in inoculum size produced moderate increases in the MICs and MBCs of RO23-6240.