To examine if Stx2 cytotoxicity could be modulated by O157:H7Δstx2 infection, cell viability was measured on HCT-8 cells incubated with either 100 ng/ml Stx2 alone or in presence of 4 × 108 CFU/ml O157:H7Δstx2 (O157:H7Δstx2+Stx2) and compared with HCT-8 cells incubated with O157:H7Δstx2 alone. This evidence concerns the gene STX2 and infection.