STEC (Shiga toxin-producing Escherichia coli) are a group of prevalent foodborne pathogens responsible for outbreaks of human gastrointestinal disease. There are two serologically distinct groups of Stxs, Stx1 and Stx2. There are 3 characterized subtypes of Stx1 (Stx1a, Stx1c, and Stx1d) and 7 subtypes of Stx2 (Stx2a, 2b, 2c, 2d, 2e, 2f, and 2g).