[The epidemiological aspects of a pseudotuberculosis polyclonal infection].

The plasmid profile of 489 Y. pseudotuberculosis strains, serovar 1b, isolated from patients during 23 outbreaks and in sporadic cases of the disease were studied. As revealed in this study, in foci with the heterogeneous population of Y. pseudotuberculosis, serovar 1b, outbreaks and sporadic cases of the disease were caused by the polyclonal population of the microorganism. The study showed that three types of outbreaks could be differentiated, depending on the clonal characteristics of the microorganism causing these outbreaks and the presence of the dominating clone of the causative agent. Y. pseudotuberculosis infection caused by the combination of several clones of the microorganism was designated as polyclonal infection.