Molecular characteristics of eae-positive clinical Shiga toxin-producing Escherichia coli in Sweden.

Shiga toxin (Stx)-producing Escherichia coli (STEC) can cause a wide range of symptoms from asymptomatic carriage, mild diarrhea to bloody diarrhea (BD) and hemolytic uremic syndrome (HUS). Besides the Stx, intimin, encoded by the eae gene, also plays a critical role in STEC pathogenesis. Herein, we investigated the prevalence and genetic diversity of eae among clinical STEC strains isolated from patients with diarrhea, BD, HUS as well as from asymptomatic STEC-positive individuals in Sweden with whole-genome sequencing. We found that 173 out of 239 (72.4%) of clinical STEC strains were eae positive. Six eae subtypes (ϵ1, γ1, β3, θ, ζ and ρ) were identified, which were classified into 29 different genotypes. eae and its subtype γ1 were significantly overrepresented in O157:H7 strains isolated from BD and HUS patients. ϵ1 was associated with O121:H19 and O103:H2 strains, and β3 to O26:H11 strains. The presence of stx 2+eae and stx 1+stx 2+eae was significantly more prevalent in strains from BD and HUS patients, respectively. The combination of a certain eae subtype (γ1) and stx subtype (stx 2 or stx 1+stx 2) is more likely to cause severe disease, suggesting the possibility of using eae genotypes in risk assessment of STEC infection. No association was observed between the presence of eae or subtypes or duration of stx shedding. In summary, this study demonstrated a high prevalence of eae in clinical STEC strains and considerable genetic diversity of eae in STEC strains in Sweden from 1994 through 2018, and revealed association between eae subtypes and disease severity.