Analysis of the Virulence of an Atypical Enteropathogenic Escherichia coli Strain In Vitro and In Vivo and the Influence of Type Three Secretion System
Figure 1
Lack of T3SS renders aEPEC 1711-4 unable to aggregate actin in HeLa cells and association with Caco-2 cells is decreased in the absence of T3SS. The ability of the wild-type strain 1711-4, its isogenic mutant deficient in escN, and the complemented mutant 1711-4 ΔescN (pEscN) as well to promote actin aggregation in vitro (evidence of A/E lesion formation) was examined by FAS. For actin accumulation, cells were stained with fluorescein isothiocyanate (FITC)-conjugated phalloidin (green), and bacterial (white arrow) and HeLa cell DNA was stained with DAPI (blue). No actin nucleation was observed with 1711-4 ΔescN mutant, whereas the ability of the complemented mutant to induce actin nucleation was restored (white arrowhead) (Figure 1(a)). Bacterial association was evaluated six hours after infection of differentiated Caco-2 cells. The number of viable bacteria recovered from cells infected with 1711-4 ΔescN mutant (~4.0 CFU/well) was significantly lower compared with the wild-type strain ( CFU/well) (). The association capacity of the escN mutant was restored in the 1711-4 ΔescN (pEscN) complemented strain and no statistically significant difference was observed when compared to the wild-type strain aEPEC 1711-4 () (Figure 1(b)).
