STX1A and infection: In this study, nine STEC strains, either eae-positive or eae-negative, had stx1a alone or in combination with stx1c or stx2a, stx2b, stx2c and stx2d. The Stx1c toxin subtype is reported mainly in eae-negative strains causing mild infections [63]; we found stx1c both in identified (serogroup O91) and unidentified serogroups that were eae-positive (Table 2).