[Development of an experimental rat model of intraabdominal abscess by Escherichia coli alone. II. Interactions between an intraabdominal abscess and a host].

It has been demonstrated that an intraabdominal abscess by Escherichia coli alone can be developed without fail although anaerobes or barium sulfate are not used. We investigated the properties and the influence of this abscess on the host. We took the method of bacterial implantation by insertion of a double gelatin capsules containing Escherichia coli suspension of which concentration was adjusted to five grades into the peritoneal cavity of Wister rats. Abscesses were developed in the survived rats on which live bacteria had been inoculated. Only Escherichia coli were found in these abscesses by culture whereas no death was occurred and no abscess was developed in the rats on which no bacterium or heat-killed ones had been inoculated. As for non-survivors at the 7th postoperative day, all of them died of panperitonitis and no abscess was developed. An abscess was developed without fail when live bacteria of which number within the order of 10(7) colony forming units were inoculated. Blood endotoxin concentration 24 hours after inoculation increased exponentially according to the inoculum size. However, that at the 7th postoperative day returned to the levels at zero time. Microscopic examination revealed a thick abscess wall, poor infiltration of inflammatory cells, and poor neovascularsis into the wall. These findings suggest that endotoxin is prevented from release into the blood stream since abscess contents are isolated by thick wall.