Pathogenicity of various Yersinia enterocolitica serotypes towards mice of Swiss and Balb/c strains.

Series of experiments aimed at determining LD50 of various Y. enterocolitica serotypes toward mice of Swiss and Balb/c strains infected by different route have been made. It appeared impossible to establish the LD50 in mice of Swiss strains after a single and repeated intravenous infection. Attention has been paid to a clear relationship between the mortality of Balb/c mice and culture conditions of Y. enterocolitica strains used for infection. In regard to particular serotypes LC50 could be determined on different days of observation and with various routes of infection of Balb/c mice. However, it concerned only those mice groups which were given suspensions of bacteria or broth culture incubated for 72 hrs at 22 degrees C. Irradiated Balb/c mice were more susceptible to infection with all serotypes of Y. enterocolitica. In the course of oral infection of Balb/c mice with serotypes IA and V of Y. enterocolitica it was possible to check the development of pathological lesions in gut and other organs, this did not refer, however, to Y. enterocolitica serotypes IB, II, III, IV, and VI.