Susceptibility of Conventional and Germfree Mice to Lethal Effects of Endotoxin

Abstract

SummaryGermfree mice of the NIH and Lobund strains, as well as specific pathogen-free mice, are significantly more resistant to the lethal effect of endotoxin, derived from E. coli strains indigenous to the mouse, than conventional mice of the same genetic stock. Conventional NIH mice were generally more susceptible to E. coli endotoxin than conventional Lobund mice. The NIH conventional mice harbored 10–100 times more coliform bacteria in their intestinal contents than the Lobund conventional mice. Differences in the gram-positive flora were also noted. Whereas conventionalization of germfree mice or SPF mice enhanced their susceptibility to endotoxin, contamination of germfree mice or SPF mice with single strains of E. coli failed to increase susceptibility to endotoxin.