Host defence and bacterial growth in fosfomycin-treated peritonitis. Experimental observations in pigs.

An approximately steady state of bacterial density intraperitoneally has been observed in bacterial peritonitis. This state, which follows an initial (0-4 h) phase of rapid elimination of bacteria, was now studied in a model of porcine peritonitis. Twelve pigs were intra-abdominally infected with 10(10) CFU each of Escherichia coli and Bacteroides fragilis. Six of the pigs received no antibiotic and six were given two doses of fosfomycin (anti-aerobic), 1 g i.v., with the aim of disturbing possible equilibrium between rapid proliferation and destruction of the sensitive E. coli. Levels of fosfomycin up to 90 times the minimum inhibitory concentration (1 mg/l) were detected in the peritoneal exudate, but the antibiotic had no discernible effect on E. coli density or elimination pattern compared with B. fragilis in the same pig or with observations in controls. The results favoured the concept of slow-replicating E. coli and hence declining activity of the defence mechanisms a few hours after the induction of peritonitis.