Spores of the C. difficile ΔbclA3 mutant strain exhibited a significant decrease in spore entry into Caco-2 cells, but not adherence to monolayers of Caco-2 cells was observed upon infection with C. difficile spores ΔbclA3 mutant in the presence of Fn (Fig. 5f, g) and Vn (Fig. 5h, i). This evidence concerns the gene VTN and infection.