Pathogenicity of Yersinia enterocolitica serotype O3 biotype 3 strains.

It is known that Yersinia enterocolitica infection in Japan is caused mainly by serotype O3 biotype 4 strains. Recently, however, a number of serotype O3 strains which were classified biotype 3 and which ferment lactose and xylose, instead of sorbose, and give a negative Voges-Proskauer reaction have been isolated from both humans and animals. In this study, comparisons of four properties were made among isolates of Y. enterocolitica serotype O3 biotype 3 from humans, pigs, dogs, cats, and rats and the laboratory stock strains of Y. enterocolitica biotype 4. All strains were tested for the presence of plasmids, calcium-dependent growth at 37 degrees C, autoagglutination activity at 37 degrees C, and recovery of the organisms from the stools of intravenously challenged mice. Biotypes 3 and 4 were positive for these four properties. Plasmid digestion with restriction endonucleases showed the same digestion patterns in both biotypes. These results suggest that Y. enterocolitica serotype O3 biotype 3 strains are pathogenic, as are biotype 4 strains.