14 ADHESION OF YERSINIA ENTEROCOLITICA TO HELA CELLS AND RABBIT SMALL INTESTINE

Abstract

The presence of a 40-50 megadalton plasmid is a prerequisite for the expression of virulence of Yersinia enterocolitica. Both chromosomal and plasmid genes seem to be involved in controling the interaction between host cells and the bacterium. In this study, the adhesive properties of Y. enterocolitica were studied by means of two different in vitro assay systems. Adhesion to human epithelial cells was measured by direct microscopy of HeLa cells cultivated on coverslips and incubated with bacteria at 37°C. The capability to adhere to the small intestine of rabbits was evaluated by incubation of small disks of intestine with 3M-labeled bacteria at 37°C, followed by washing and finally determination of the retained, intestinal-associated radioactivity by means of liquid scintilation. The bacterial strains studied were Y. enterocolitica serotype 0:3, harbouring the virulence plasmid (Ye03P+), its isogenic plasmidless derivate (Ye03P-), and the non-pathogenic plasmidless serotype 0:7 (Ye07P-). Ye03P+ as well as Ye03P- adhered extensively to HeLa cells; Ye07P- did not adhere at all. However, while adherence of Ye03P+ to disks of intestinal tissue was considerable, Ye03P- and Ye07P- both adhered to only a small degree. Thus, this study demonstrates that even if pathogenic strains of Y. enterocolitica are capable of adhering to HeLa cells by means of chromosomal genes alone, plasmid encoded properties are necessary for adhesion to the intact mucosal surface, indicating that the binding to cell culture lines differ from the binding to intestine.