FIG. 5.

Internalization of L. monocytogenes, S. typhimurium, P. mirabilis, and E. coli by confluent Caco-2 and HT-29 enterocytes that had been either untreated or preincubated for 1 h in either calcium-free medium, 1 μg of cytochalasin D per ml, or calcium-free medium followed by an additional 1-h incubation with cytochalasin. Horizontal lines indicate lower limit of assay detection. Error bars are not apparent if <0.1. Significant change in the numbers of bacteria internalized by treated enterocytes compared to the numbers of bacteria internalized by corresponding control, untreated enterocytes: ∗, P < 0.01; †, P < 0.05. For both HT-29 and Caco-2 enterocytes, there are no significant differences in the numbers of bacteria internalized by enterocytes treated with cytochalasin alone compared to the numbers internalized by enterocytes incubated in calcium-free medium prior to cytochalasin treatment, with the exception of P. mirabilis incubated with HT-29 enterocytes, where the numbers of internalized proteus are greater in enterocytes incubated in the calcium-free medium prior to the cytochalasin treatment: ‡, P < 0.05.