Surface properties of Yersinia species and epithelial cell interactions in vitro by a method measuring total associated, attached and intracellular bacteria.

A procedure was developed for enumeration of total associated, attached and intracellular bacteria after interaction of Yersinia spp. with epithelial cells in vitro. Isogenic cultures of Y. enterocolitica grown at 25 degrees C had greater affinity for epithelial cells (Henle, HeLa and Vero) than for polystyrene, and they invaded the cells. Y. kristenseni and Y. intermedia showed less attachment to either surface and were non-invasive. The degree of attachment to cells and invasion by Y. enterocolitica was related to number of bacteria added and interaction time, whereas attachment to polystyrene occurred rapidly and did not change. Y. enterocolitica was more hydrophobic when grown at 35 degrees C than at 25 degrees C according to partitioning in a biphasic dextran-polyethylene glycol system, and attached strongly to both polystyrene and epithelial-cell monolayers. Y. kristenseni grown at 25 degrees C was also hydrophobic but did not have the same attachment properties. Y. kristenseni and Y. intermedia showed slightly reduced electrostatic interactions with the anion exchangers DEAE-Sepharose and DEAE-Trisacryl. Attachment of Y. enterocolitica to epithelial cells probably involves non-specific surface properties that are not entirely explicable by hydrophobic and electrostatic interactions, whereas invasion of epithelial cells appears to resemble "receptor-mediated endocytosis".

Some conditions influencing the association of Yersinia enterocolitica with epithelial cells in vitro.

The association of Yersinia enterocolitica serotype 0:5,27 with Henle 407 epithelial cells in vitro was measured by using 35S-labelled bacteria with separation of unassociated bacteria by filtration (Nuclepore polycarbonate 5-micron membrane). The number of associated bacteria was related to the initial multiplicity. Changes in beginning pH, the presence of protein, availability of Ca2+ and Mg2+, and nature of carbohydrate in a defined bacterial growth medium did not change the degree of epithelial cell association. Bacteria recovered from the log phase of growth at 25 degrees C, or after growth to stationary phase at 35 degrees C, showed no association with epithelial cells. Optimal association occurred when the pH provided during interaction was between 7.6 and 8.6 and the temperature was either 25 or 35 degrees C. No association occurred within 30 min at 4 degrees C. The presence of Ca2+ and (or) Mg2+ during interaction had no effect, but the addition of peptone increased association. The results of this study demonstrate the importance of controlling both conditions provided for bacterial growth and those provided for interaction to achieve optimal association of Y. enterocolitica with epithelial cells in vitro.

Epithelial cell association and hydrophobicity of Yersinia enterocolitica and related species.

Six of 11 test strains of Yersinia enterocolitica and related species that carried other markers of pathogenicity were found to associate with Henle 407 epithelial cells in vitro. All Henle-positive strains were hydrophobic when tested by hydrophobic interaction chromatography with phenyl-Sepharose and by partitioning in an aqueous-hexadecane mixture. Hydrophobicity was also exhibited by some of the Henle-negative strains. None of the test strains aggregated in low concentrations of ammonium sulphate, suggesting that protein structures such as fimbriae were not involved in hydrophobicity or epithelial cell association.