Genetic profiles of Shiga toxin and intimin genes found in stool broth cultures: a 2-year reference laboratory study

Abstract

Shiga toxin (Stx)-producing Escherichia coli (STEC) are associated with potentially serious illness in humans. STEC detection is often based on the presence of Stxs, Stx 1 and/or Stx 2, and intimin, encoded by the eae gene. A 2-year collection of stool broth cultures was tested for variants of stx 1, stx 2, and eae. Approximately 80% (138 of 174) were positive for stx 1 and/or stx 2, with stx 1 as the most prevalent (66%). Of the stx 1 variants, stx 1 was the most common (76%) followed by stx 1c (22%). Analysis of stx 2-positive isolates found 20 (53%) stx 2, 13 (34%) stx 2/ stx 2v-ha, 3 (8%) stx 2v-ha, 1 (3%) stx 2v-hb, and 1 (3%) stx 2d-activatable. Findings of stx 2/ stx 2v-ha and stx 2d-activatable are noteworthy given associations with hemolytic uremic syndrome and increased cytotoxicity, respectively. Of the Stx positive, 94 (68%) were eae positive with 31 (33%) eae ɛ1, 19 (20%) eae γ1, and 18 (19%) eae β1. A predominance of eae ɛ1 may suggest a new pathogenic significance because, reportedly, eae β1 is one of the most widespread variants.