Molecular Characterization of the Enterohemolysin Gene ( ehxA ) in Clinical Shiga Toxin-Producing Escherichia coli Isolates

Shiga toxin (Stx)-producing (STEC) is an important foodborne pathogen with the ability to cause bloody diarrhea (BD) and hemolytic uremic syndrome (HUS). Little is known about enterohemolysin-encoded by . Here we investigated the prevalence and diversity of in 239 STEC isolates from human clinical samples. In total, 199 out of 239 isolates (83.26%) were positive, and was significantly overrepresented in isolates carrying + ( < 0.001) and ( < 0.001). The presence of was significantly associated with BD and serotype O157:H7. Five subtypes were identified, among which, subtypes B, C, and F were overrepresented in -positive isolates. All O157:H7 isolates carried subtype B, which was related to BD and HUS. Three groups were observed in the phylogenetic analysis, namely, group Ⅰ ( subtype A), group Ⅱ ( subtype B, C, and F), and group Ⅲ ( subtype D). Most BD- and HUS-associated isolates were clustered into group Ⅱ, while group Ⅰ was associated with non-bloody stool and individuals ≥10 years of age. The presence of + and + was significantly associated with HUS and O157:H7 isolates. In summary, this study showed a high prevalence and the considerable genetic diversity of among clinical STEC isolates. The genotypes (subtype B and phylogenetic group Ⅱ) could be used as risk predictors, as they were associated with severe clinical symptoms, such as BD and HUS. Furthermore, , together with and can be used as a risk predictor for HUS in STEC infections.