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-μm 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 °C, or after growth to stationary phase at 35 °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 °C. No association occurred within 30 min at 4 °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.