[The results of the measured oral infection of white mice with strains of the causative agent of plague differing in their plasmid profile].

The oral infection of mice with Y. pestis culture with different plasmid profiles by the method of feeding them with agar granules containing a definite number of these bacteria revealed that the virulence of subcultures which had lost Pst-plasmid and the capacity for fibrinolysin and plasma-coagulase production, encoded by this plasmid, decreased 10-1000 times, the loss of Fra-plasmid produced a less pronounced effect. In contrast to subcutaneous infection, in alimentary infection Y. pestis culture grown at 28 degrees C was more virulent than that grown at 37 degrees C. During the first hours after infection Y. pestis could be detected only in the lymph nodes along the gastrointestinal tract and in the intestine walls; later generalization of the infectious process or its latent course was observed. After oral infection specific antibodies were detected in surviving animals (up to 35%).