In-vitro activity of enoxacin against aminoglycoside-resistant gram-negative bacilli and other clinical isolates.

The in-vitro activity of enoxacin was tested against 500 clinical isolates of Gram-negative bacilli that were resistant to one or more of gentamicin, tobramycin and amikacin, and against 1060 recent consecutive clinical isolates of Gram-negative bacilli and Gram-positive cocci. Enoxacin was active against staphylococci (MICs less than or equal to 4 mg/l) but less active against Streptococcus faecalis (MICs mostly 8 mg/l). It was active against Pseudomonas aeruginosa (MICs 0.5-4 mg/l) and very active against Enterobacteriaceae. In the series of consecutive isolates 97% of Enterobacteriaceae had MICs less than or equal to 1 mg/l. The aminoglycoside-resistant series of Enterobacteriaceae included more strains with higher MICs (13% were 2-4 mg/l and 10% were greater than or equal to 8 mg/l); the majority of the isolates with MICs greater than or equal to 8 mg/l); the majority of the isolates with MICs greater than or equal to 8 mg/l were Serratia marcescens and Providencia spp. Among the non-fermenting species the least sensitive were Acinetobacter calcoaceticus and Ps. maltophilia. Enoxacin-resistant strains of Enterobacteriaceae were resistant to nalidixic acid, but nalidixic acid-resistant strains ranged from fully sensitive to highly resistant to enoxacin.