COMPARISON OF PLASMIDS OF STRAINS OF YERSINIA-ENTEROCOLITICA BIOVAR 1A WITH THE VIRULENCE PLASMID OF A PATHOGENIC Y-ENTEROCOLITICA STRAIN

The plasmid content of apathogenic Y.enterocolitica biovar 1A strains was determined and the plasmids were compared with the virulence plasm id of a pathogenic Y.enterocolitica strain. About 38% of the selected biovar 1A strains contained plasmids of different sizes ranging from 2 .7 kb to more than 70 kb. Some of the larger plasmids had a size simil ar to that of the virulence plasmid of a pathogenic reference strain. The restriction patterns of these plasmids were different from the res triction pattern of the virulence plasmid of the pathogenic reference strain. Differences were also observed in hybridization studies with t he virulence plasmid. The plasmids from 15 out of 16 biovar 1A strains showed no homology,whereas the plasmid of one biovar 1A strain partia lly hybridized to the virulence plasmid.