Since infections of EHEC expressing Stx2a are associated with a higher risk for the development of HUS [114,115] and the most dangerous and fatal outbreak strains such as EHEC O157:H7 [2,116,117,118,119] or O104:H4 [120,121] do express Stx2a, we used this Stx subtype in our study to determine its cytotoxic activity on human colon Caco-2 and HCT-8 epithelial cell lines. This evidence concerns the gene STX2 and infection.