Factors contributing to the reduced invasiveness of chlorine-injured Yersinia enterocolitica.

The invasion of epithelial cells in vitro and in vivo by chlorine-injured Yersinia enterocolitica was assessed by direct microscopic observations. These experiments showed that injury by chlorine inhibited invasiveness of virulent Y. enterocolitica. Two requirements appeared to be necessary for invasiveness: the organism must be viable and metabolically active, and the organism must have certain surface components to initiate engulfment. Inhibition of RNA synthesis by rifampin and protein synthesis by chloramphenicol, tetracycline, and spectinomycin inhibited the invasiveness but not the attachment of Y. enterocolitica to epithelial cells. Membrane preparations from untreated and antimicrobial-agent-treated Y. enterocolitica blocked the invasiveness of virulent Y. enterocolitica, whereas membranes from chlorinated cells were unable to block invasiveness. Chlorine did not change the hydrophobicity or surface charge of injured Y. enterocolitica. The results indicate that invasion was more than simple association of the bacterium with the epithelial cell and involved a specific trigger to stimulate engulfment.