Studies on the Pathogenicity of Yersinia Enterocolitica and Y. Enterocolitica‐like Bacteria.

A total of 412 strains of Yersinia enterocolitica and Y. enterocolitica-like bacteria were examined for their ability to interact with HeLa cell monolayers. Of 331 isolates from environmental sources in Scandinavia, only three strains biochemically classified as Y. pseudotuberculosis were invasive for HeLa cells. Invasiveness was also indicated for one strain (O-serogroup 2) from a disease goat. Another eight strains adhered firmly to the cell surface in great numbers. All of 22 strains belonging to O-serogroup 3 from human patients with gastroenteritis were invasive. Seven strains of O-serogroup 3 from small rodents and water were non-invasive. Among 33 reference strains representing Y. enterocolitica O-serogroup 1-34, invasiveness was indicated for strains with known pathogenicity (O-serogroup 1, 2, 3, 5-27, 8, 9). However, some strains belonging to O-serogroups with uncertain clinical significance were also invasive for HeLa cells. A close correlation between invasiveness and enterotoxin production was demonstrated for the 22 human clinical isolates belonging to O-serogroup 3.