Investigation of the potential role of Enterococcus faecalis in the pathophysiology of experimental peritonitis

Abstract

Two nonfatal models of peritonitis differing by the duration and the severity of the disease were studied in rats by implantation of Escherichia coli and Bacteroides fragilis with or without increasing concentrations of Enterococcus faecalis. Results were evaluated at 3 or 6 days after inoculation. The highest enterococcal concentrations (10(9) cfu/mL) enhanced the severity of the infection, evident by increased emaciation, increased peritoneal counts of E. coli and B. fragilis, and increased frequency of E. coli and B. fragilis bacteremia compared with enterococcus-free animals. Six therapeutic regimens (low-dose amoxicillin + low-dose gentamicin, high-dose amoxicillin + high-dose gentamicin, pefloxacin, ornidazole, pefloxacin + ornidazole, imipenem + gentamicin) were tested. All treatments failed to eradicate E. faecalis except the combination pefloxacin + ornidazole, which achieved a significant reduction of local bacterial counts and suppressed bacteremia. Enterococcus played an important role in the mechanisms of bacterial synergy in experimental peritonitis. However, eradication of enterococcus did not seem possible by conventional antienterococcal therapy.