The granuloma pouch: an in vivo model for pharmacokinetic and chemotherapeutic investigations. II. Microbiological characterization.

In this paper we have described the microbiology of the granuloma pouch model in rats. We studied the biochemical parameters of pouch exudates infected with Escherichia coli. Data revealed that the inflammatory response increased during the course of infection since lactate dehydrogenase levels as well as alpha 2 and gamma-globulin fractions were increased in comparison to uninfected controls. Infection of the pouches did not spread. We also monitored the growth characteristics of four different E. coli strains. In vitro incubation of these strains in human and rat serum as well as in pouch exudate, and the in vivo growth rate in infected pouches revealed that the degree of serum sensitivity was clearly related to viability in vivo. Serum-resistant strains grew well in pouch exudate, whereas serum-sensitive strains were eliminated from the infected pouches. Since elimination of these strains was dependent on the challenge dose, we concluded that cellular and/or humoral host defense mechanisms became locally exhausted or inactivated. Thus, the granuloma pouch represents a local bacterial infection of a poorly defended, inflamed body cavity.