Summary

Host defence mechanisms associated with the inhibition of translocation of bacteria from the gastrointestinallGI) tract were investigated in SCID and beige mice after decontamination with oral antibiotics and colonization with Escherichia coli C25. SCID mice, which have impaired T and B cell function, tended to have a greater incidence of bacterial translocation from the GI tract up to 7 days after inoculation compared with controls. However, after 7 days both SCID and controls cleared the E. coli C25 from the liver, spleen, blood and peritoneal cavity. Beige mice, with impaired NK cell and polymorphonuclear leukocyte function, were not able to clear the inoculated bacteria from their liver by 14 days after inoculation although the controls were cleared by 7 days. Numbers of bacteria in the mesenteric lymph nodes IMLN) of beige mice did not decrease significantly by 14 days after inoculation, whereas numbers in SCID mice decreased markedly within 7 days. These results suggest that defence mechanisms other than T and B cell function are important in the inhibition of systemic infection from the GI tract. Keywords Bacterial translocation; beige mice; gastrointestinal tract; SCID mice Bacterial infection is a frequent and severe problem in patients who are immuno-compromised, e.g. by thermal injury, cancer or acquired immunodeficiency syndrome (AIDS).More attention has been focused on infections caused by exogenous microorgan-isms than those caused by the endogenous microflora of the gastrointestinal (GIl tract. However, recent studies in animal models have demonstrated that both endogenous and exogenous bacteria colonizing the GI tract were potential sources of septicaemia (Deitch 19901.The passage of viable endogenous bacteria from the GI tract through the epithelial mucosa to the mesenteric lymph nodes IMLN) and other organs has bee