Interaction of E. coli strains with eukaryotic cells. Eukaryotic cells were infected with E. coli V2846 (AdpC), V2848 (AdpD), and V2720 (pET30 only) as described in Materials and Methods. Total association (A, C, and E) and invasion (B, D, and F) of E. coli strains into host cells were determined by the quantification of viable bacteria by counting of CFU. Results from an experiment performed in triplicate are shown. (A and B) NIH 3T3 fibroblasts. (C and D) HUVECs. (E and F) Oral epithelial HN4 cells.