Activity of ciprofloxacin in the treatment of experimental intra-abdominal abscesses in mice.

The therapeutic efficacy of ciprofloxacin in the treatment of experimental intra-abdominal abscesses in mice caused by a strain of Staphylococcus epidermidis was compared with that of ampicillin and clindamycin. The abscesses were produced by intraperitoneal administration of a bacterial suspension obtained by bacterial culture of S epidermidis diluted to 10(8) CFU/ml mixed with sterilized rat feces and barium sulphate in male BALB/C mice. The following doses of antibiotics were given twice a day for seven days: ciprofloxacin, 1 microgram/100 microliters; clindamycin, 1.5 micrograms/100 microliters; and ampicillin, 3.6 micrograms/100 microliters. The antibiotic serum and pus concentrations were also determined by an agar well diffusion assay. The maximum serum concentrations were obtained 30 minutes after intraperitoneal administration (ciprofloxacin, 2.7 micrograms/ml; clindamycin, 9.0 micrograms/ml; ampicillin, 3.9 micrograms/ml). The penetration inside the abscess was also satisfactory (ciprofloxacin, 0.51 microgram/ml; clindamycin, 3.4 micrograms/ml; ampicillin, 3.8 micrograms/ml). A favorable clinical and bacteriologic response was obtained in 69% of the mice following the ciprofloxacin treatment and in 56% following ampicillin. The efficacy of ciprofloxacin was much higher than that of clindamycin and ampicillin, presumably because of its much higher intrinsic potency against the pathogen rather than for its pharmacokinetic characteristics and its penetration inside the abscess.