INTERACTIONS OF YERSINIA-ENTEROCOLITICA WITH POLARIZED HUMAN INTESTINAL CACO-2 CELLS

The in vitro interactions of Yersinia enterocolitica, Salmonella typhi murium and Escherichia coli with polarized human colonic carcinoma (Ca co-2) cells are described. Invasion of a confluent Caco-2 cell monolay er by Yersinia and Salmonella took place within 4 h after contact, whi ch was in marked contrast to E. coli which did not invade Caco-2 cells . Cytoplasmic extrusions developed on the apical membrane and indicate d the site of entrance of bacteria into the Caco-2 cells. Intracellula r Yersinia and Salmonella were surrounded by a vacuolar membrane. Sing le as well as multiple bacteria were enclosed within a single vacuole. At 6 h after contact some of the intracellular yersiniae were found f ree in the cytoplasm. Furthermore, morphological signs of degeneration of Caco-2 cells such as vacuolization and autophagy were observed. Ca co-2 cells infected with Salmonella also showed degenerative changes b ut the salmonellae resided within membrane-bound vacuoles in contrast to Yersinia. These observations are in contrast to those described for the invasion of other cell lines (not derived from intestinal epithel ium) by Yersinia and may reflect more closely the interactions between Yersinia and the intestinal epithelium during gastrointestinal infect ion.