A mouse model for postoperative fatal enteritis due to Staphylococcus infection

Background. Postoperative infection of intestine with methicillin-resistant Staphylococcus aureus (MRSA) is fatal in some cases. The object of this st udy was to establish a mouse model for the infection, providing a useful to ol for investigating mechanisms in the progression of infection. Methods. Mice were pretreated with cyclophosphamide, injected orally or dir ectly into jejunum with MRSA prepared from a postoperative patient, and the n given 5 daily doses of antibiotics. Forty-eight hours after the injection , bacterial translocation and serum endotoxin levels were examined. Macroph age depletion was carried out by the administration of liposome-encapsulate d dichloromethylene diphosphate (Cl2MDP), 4 days before MRSA injection. Results. Injection into the jejunum but not oral administration of MRSA ind uced enteritis with diarrhea and resulted in death in most cyclophosphamide -treated mice. Translocation of MRSA in mesenteric lymph nodes and liver wa s observed, concomitantly with E. coil infection. Endotoxin-resistant C3H/H eJ 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 cyc lophosphamide, Conclusion. We established a mouse model for the fatal MRSA infection which induced enteritis with diarrhea, that will be a useful tool for investigat ing the mechanisms for sometimes fatal MRSA infection of the intestine in p ostoperative patients. The presence off. coli or endotoxin seemed to play a major role in the mortality of mice in the early days of MRSA-induced ente ritis, but other factors, probably from MRSA, in the later days. Phagocytes were quite important for protection against thee MRSA infection. (C) 2001 Academic Press.