A RAT MODEL OF NONLETHAL BACTERIAL-INFECTION

The purpose of the study was to develop a small animal model of intrap eritoneal infection without mortality and with a catabolic response to the infection, viz. to mimic the clinical situation in man. Intraperi toneal infection was induced in female Wistar rats by deposition of a gelatin capsule containing a mixture of Escherichia coli and Bacteroid es fragilis and adjuvant substances. Seven groups of animals were infe cted with different bacterial inocula (0.2-4.3x10(6) CFU) to establish reproducible and dose-dependent changes in mortality, body weight in relation to food intake, blood cultures, peripheral blood leukocyte co unts, and abscess formation on autopsy. No mortality was observed in a nimals with an inoculum below 2.2x10(6) CFU in spite of positive blood cultures. Initial weight loss was followed by weight gain in all anim als except the group infected with the low inoculum (0.2x10(6) CFU). T his group had no mortality, was in a catabolic state for three days, i ndicated by weight loss in spite of nearly normal food intake, and the infectious state was supported by intraperitoneal dissemination of sm all abscesses. The low-grade character of the infection was reflected by changes in peripheral blood lymphocyte and neutrophil granulocyte c oncentrations. In conclusion, this study presents a small animal model with a reproducible dose response to the bacterial challenge, allowin g prolonged studies of metabolic changes following infection.