STX1A and hemolytic-uremic syndrome: Four subtypes of Stx1 (Stx1a, Stx1c, Stx1d, Stx1e) and seven subtypes of Stx2 (Stx2a-g) have been identified, of which especially the Stx2 variants Stx2a and Stx2c are commonly associated with HUS development in humans (Melton-Celsa, 2014).