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

• Main Authors: Ying Hua, Ji Zhang, Cecilia Jernberg, Milan Chromek, Sverker Hansson, Anne Frykman, Yanwen Xiong, Chengsong Wan, Andreas Matussek, Xiangning Bai
• Format: Article
• Language: English
• Published: MDPI AG 2021-01-01
• Series: Toxins
• Subjects: Shiga-toxin-producing <i>Escherichia coli</i>; enterohemolysin; <i>ehxA</i>; gene diversity; hemolytic uremic syndrome; clinical significance
• Online Access: https://www.mdpi.com/2072-6651/13/1/71

Shiga toxin (Stx)-producing <i>Escherichia coli</i> (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 <i>ehxA</i>. Here we investigated the prevalence and diversity of <i>ehxA</i> in 239 STEC isolates from human clinical samples. In total, 199 out of 239 isolates (83.26%) were <i>ehxA</i> positive, and <i>ehxA</i> was significantly overrepresented in isolates carrying <i>stx</i>_2a + <i>stx</i>_2c (<i>p</i> < 0.001) and <i>eae</i> (<i>p</i> < 0.001). The presence of <i>ehxA</i> was significantly associated with BD and serotype O157:H7. Five <i>ehxA</i> subtypes were identified, among which, <i>ehxA</i> subtypes B, C, and F were overrepresented in <i>eae</i>-positive isolates. All O157:H7 isolates carried <i>ehxA</i> subtype B, which was related to BD and HUS. Three <i>ehxA</i> groups were observed in the phylogenetic analysis, namely, group Ⅰ (<i>ehxA</i> subtype A), group Ⅱ (<i>ehxA</i> subtype B, C, and F), and group Ⅲ (<i>ehxA</i> subtype D). Most BD- and HUS-associated isolates were clustered into <i>ehxA</i> group Ⅱ, while <i>ehxA</i> group Ⅰ was associated with non-bloody stool and individuals ≥10 years of age. The presence of <i>ehxA</i> + <i>eae</i> and <i>ehxA</i> + <i>eae + stx</i>₂ was significantly associated with HUS and O157:H7 isolates. In summary, this study showed a high prevalence and the considerable genetic diversity of <i>ehxA</i> among clinical STEC isolates. The <i>ehxA</i> 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, <i>ehxA</i>, together with <i>stx</i> and <i>eae,</i> can be used as a risk predictor for HUS in STEC infections.