ADHERENCE AND TOXICITY OF YERSINIA ENTEROCOLITICA 0:3 AND 0:9 CONTAINING VIRULENCE‐ASSOCIATED PLASMIDS FOR VARIOUS CULTURED CELLS

Plasmid (47 and 44 Mdal, respectively) containing strains of Yersinia enterocolitica 0:3 and 0:9 adhered to and were toxic for HEp-2 human epithelial and Y-1 adrenal cells in vitro, At 37 degrees C, but not at room temperature, the adhesion of the bacteria lead to rounding and partial detachment of the cultured cells. UV-inactivated plasmid-positive Y. enterocolitica were neither adherent nor toxic for the cells but were readily endocytosed by HEp-2 cells. The adherence of plasmid-positive Y. enterocolitica 0:3 and 0:9 on epithelial cells may be pathogenetically important as an initial step for intestinal colonization, and possibly in Y. enterocolitica-induced diarrhoea. Plasmid-positive Y. enterocolitica also adhered to the surface of cultured human macrophages and were apparently not phagocytosed as effectively as the plasmid-negative derivatives of the same bacteria. Thus resistance to phagocytosis may form an additional plasmid-dependent virulence property of Y. enterocolitica 0:3 and 0:9.