While Philpott and colleagues have demonstrated that translocation of purified Stx1 across polarized T84 cells is not altered by simultaneous infection with an Stx-negative STEC laboratory variant (Philpott et al., 1997), recent studies have shown stimulation of uptake and/or transcytosis of purified Stx1 by incubation with STEC Stx-deletion mutants or lysates (Lukyanenko et al., 2011; In et al., 2013). This evidence concerns the gene STX1A and infection.