Differences in Susceptibility to Peroral Inoculation with Bacillus piliformis Spores in Rats and Mice

Abstract

The median liver lesion producing doses of peroral inoculation with the spores of Tyzzer's organism RJ strain were 10^4.3 in rats and 10^2.7 in rats receiving prednisolone treatment for the provocation of Tyzzer's disease. In contrast to rats, liver lesions were detected in few mice inoculated perorally with 10⁷ spores. In mice inoculated perorally with 10⁷ spores, excretion of infective spores in the feces was detected only on day 1 postinoculation. On the other hand, no difference in suceptibility between rats and mice was detected upon intravenous inoculation with vegetative cells of the RJ strain. These results suggest that germination of the spores in the intestinal tract causes the difference in the susceptibility in rats and mice.