Characteristics of the internalization and intracellular survival of Campylobacter jejuni in human epithelial cell cultures.

The characteristics associated with the internalization and intracellular behavior of Campylobacter jejuni during short-term and long-term cultivation with INT 407 cells were examined. The internalization of C. jejuni by INT 407 cells was inhibited by cytochalasin dansylcadaverine, chemicals that disrupt microfilament formation and inhibit receptor cycling, respectively. Ammonium chloride and methylamine, two chemicals that inhibit endosomal acidification, did not affect C. jejuni internalization. Once internalized, C. jejuni were found exclusively with membrane-bound vacuoles. With regard to intracellular survival, a decline in the number of viable intracellular bacteria, as determined by protection from gentamicin, occurred during the initial phase of infection and when a low level of the antibiotic was maintained in the culture medium. However, the number of intracellular C. jejuni increased markedly after the removal of the antibiotic. In the absence of antibiotic, the infection led to the deterioration of the cell monolayers, indicating that C. jejuni is able to survive within epithelial cells and elicit a cytotoxic effect. The ability of C. jejuni to enter and exert deleterious effects on cells may reflect a pathogenic mechanism associated with enteritis caused by this organism.