A review. Lessons from an animal model of intra-abdominal sepsis.

Intra-abdominal sepsis that involves multiple aerobic and anaerobic bacteria derived from the colonic flora was studied in Wistar rats to determine the relative roles of various microbial species. The rats challenged with pooled colonic contents showed a biphasic disease. Initially, there was acute peritonitis, Escherichia coli bacteremia, and high mortality. In rats that survived this acute peritonitis stage, intra-abdominal abscesses developed, and anaerobic bacteria were the preponderant organisms. Subsequent experiments showed that antibiotics directed against coliforms prevented mortality, whereas agents active against anaerobes reduced the incidence of abscesses. Challenges with Escherichia coli alone produced bacteremia and death, whereas pure cultures of Bacteroides fragilis caused intra-abdominal abscesses. These observations suggest that both coliforms and anaerobes are important pathogens in intra-abdominal sepsis, although the different types of microbes appear to play distinctive roles in the sequence of pathological events.