Histopathological studies on experimental Yersinia enterocolitica infection in animals

Experiments were made using mice, rabbits, and monkeys. Mice were divided into 2 groups: an intravenously injected group and an orally administered one. In either group, lesions were found mainly in mucous membranes on Peyer's patches of intestines. Lesions consisted of formation of bacterial colonies accompained by accumulation of neutrophils and histiocytes, and proliferation of reticulum cells. Severe intestinal lesions were common to the 3 animals. Apart from the intestines, the liver showed most remarkable changes. Next ranked changes in bone marrows and spleen. Mesenteric lymph nodes revealed no significant changes. On the other hand, nonpathogenic strains caused little change.