New virulence-associated plasmid in Yersinia enterocolitica.

In a study of 103 strains of Yersinia enterocolitica, 10 strains were found to be lethal for mice and to possess 42- and 82-megadalton plasmids. This association was statistically significant (P much less than 0.001). Serotypes of Y. enterocolitica previously considered avirulent were found to possess these plasmids and to be lethal for mice. A spontaneous derivative of one strain contained only the 82-megadalton plasmid and was lethal for mice anyway. This virulence-associated plasmid is a potential diagnostic tool for the clinical or public health laboratory which must delineate pathogenic strains of Y. enterocolitica.