Multicenter study of ofloxacin activity on bacteria isolated from a hospital environment

: Minimal inhibitory concentrations (MICs) of ofloxacin were evaluated by agar dilution for 1508 bacterial strains isolated in five hospitals. For Enterobacteriaceae sensitive to nalidixic acid, MICs ranged from 0.008 to 1 microgram/ml (mode MIC: 0.12); the different species of Enterobacteriaceae exhibited similar mode MICs (0.12) with the exception of E. coli (0.06-0.12), P. mirabilis (0.5) and Providencia (0.25). Among strains intermediate and resistant to nalidixic acid, most of which were Serratia, Providencia and Citrobacter, 41% had a MIC within the susceptibility range, while the others had a MIC of 2 to 8 micrograms/ml, or even 64 micrograms/ml in a few instances. Ofloxacin also exhibited satisfactory activity against P. aeruginosa, with MICs ranging from 0.25 to 16 micrograms/ml (mode MIC: 2) for 87% of strains, and A. calcoaceticus, with MICs from 0.25 to 2 micrograms/ml (mode MIC: 1). Haemophilus sp. (MIC: 0.008 to 0.06 microgram/ml; mode MIC: 0.03), Gonococci (mode MIC: 0.008), and Meningococci (mode MIC: 0.016) were very sensitive to ofloxacin. The spectrum of ofloxacin included Gram positive cocci: MICs of Staphylococci were 0.06 to 2 micrograms/ml (mode MIC: 0.5); Enterococci, other Streptococci and Pneumococci were less sensitive, with MICs of 2 to 4 micrograms/ml for the majority of strains. As for anaerobic bacteria, ofloxacin proved more active against Clostridium (0.5 to 2 micrograms/ml) than Bacteroides (0.5 to 16 micrograms/ml).