Comparative efficacy of pefloxacin and six other antimicrobial agents on Staphylococcus aureus experimental abscesses.

Pefloxacin (Pef) is a new quinolone which has been shown to have good in-vitro activity against Staphylococcus aureus, and to reach high tissue concentrations. Its efficacy was compared to that of 2 quinolone derivatives, norfloxacin (Nor) and ciprofloxacin (Cip) and to that of methicillin (Meth), cephalothin (Cep), pristinamycin (Pri) and vancomycin (Van), in an experimental model of S. aureus abscesses. Mice challenged with an intramuscular thigh injection of a calibrated inoculum developed local abscesses. Three S. aureus strains (with different antibiotic resistance profiles (Pase-, Pase+, MethR)) were used. In this model, the antibiotics showing the best ED50 following oral administration, against all three strains were Pef greater than Cip greater than Pri greater than Nor, by subcutaneous administration for the Pase- strain Pef = Cip greater than Cep greater than Van; for the Pase+ strain Pef = Cip greater than Van greater than Meth and for the Pase+ MethR strain: Pef = Cip greater than Van greater than Cep. These data indicate that pefloxacin and ciprofloxacin are highly active in vivo against various strains of S. aureus, and appear to be more potent than norfloxacin, vancomycin, cephalothin and methicillin.