IN-VIVO BACTERICIDAL ACTIVITIES OF CIPROFLOXACIN AND PERFLOXACIN IN AN EXPERIMENTAL-MODEL OF SERRATIA-MARCESCENS ENDOCARDITIS

The critical concentrations of pefloxacin and ciprofloxacin in serum, corresponding to the lowest concentration in serum able to achieve a 2 -log-unit reduction in the CFU in vegetations after a 24-h exposure at a steady-state concentration obtained by a continuous intravenous inf usion, were determined in an experimental model of Serratia marcescens endocarditis in rabbits. In vitro data showed that the MICs of ciprof loxacin and pefloxacin were 0.06 and 0.25 mg/liter, respectively. The killing curves indicated a maximum killing rate at a concentration fou r times that of the MICs. In vivo, the critical concentrations of pefl oxacin and ciprofloxacin in serum were 0.4 and 0.24 mg/liter, respecti vely, corresponding to a concentration of four times the MICs.