A Mouse Model for Postoperative Fatal Enteritis Due to Staphylococcus Infection

Abstract

Background. Postoperative infection of intestine with methicillin-resistant Staphylococcus aureus (MRSA) is fatal in some cases. The object of this study was to establish a mouse model for the infection, providing a useful tool for investigating mechanisms in the progression of infection.Methods. Mice were pretreated with cyclophosphamide, injected orally or directly into jejunum with MRSA prepared from a postoperative patient, and then given 5 daily doses of antibiotics. Forty-eight hours after the injection, bacterial translocation and serum endotoxin levels were examined. Macrophage depletion was carried out by the administration of liposome-encapsulated dichloromethylene diphosphate (Cl2MDP), 4 days before MRSA injection.Results. Injection into the jejunum but not oral administration of MRSA induced enteritis with diarrhea and resulted in death in most cyclophosphamide-treated mice. Translocation of MRSA in mesenteric lymph nodes and liver was observed, concomitantly with E. coli infection. Endotoxin-resistant C3H/HeJ mice infected with MRSA survived longer than endotoxin-sensitive C3H/He mice, but also died within a week after MRSA injection. Selective depletion of macrophages induced infection in mice that were not pretreated with cyclophosphamide.Conclusion. We established a mouse model for the fatal MRSA infection which induced enteritis with diarrhea, that will be a useful tool for investigating the mechanisms for sometimes fatal MRSA infection of the intestine in postoperative patients. The presence of E. coli or endotoxin seemed to play a major role in the mortality of mice in the early days of MRSA-induced enteritis, but other factors, probably from MRSA, in the later days. Phagocytes were quite important for protection against the MRSA infection.