FIG 2.

Adherence of aEPEC 1711-4 bacteria and the corresponding deleted and complemented derivatives to Caco-2 cells. (A) Bacterial adherence to Caco-2 cells was analyzed by optical microscopy 3 h after infection. Adherence tests were performed with differentiated Caco-2 cells and bacteria with or without a centrifugation step. Bacterial clusters attached to Caco-2 cells (white arrows) were observed in assays performed with wild-type (WT) strain 1711-4 and the complemented C1P1-8, 17(pETfliD), and/or 17(pBADmotAB) derivatives. Few adherent bacteria and no clusters were observed on Caco-2 cells incubated with the 17ΔfliC, 17ΔfliD, and 17motAB mutants. Uninfected Caco-2 cells were used as a control. (B) Error bars indicate standard deviation (SD), and an asterisk indicates a statistically significant difference between aEPEC 1711-4 and each deficient mutant tested (17ΔfliD, 17ΔfliC, or 17ΔmotAB). Note the decreased adherence of the mutant derivatives with regard to the wild-type strain (∼40-fold) both in the presence and in the absence of a centrifugation step. For the complemented mutants, the number of bacteria recovered was higher (∼30-fold) than that of the wild-type strain (P < 0.005). Results are representative of three independent experiments performed in triplicate.