Genomic Characteristics of Stx2e-Producing Escherichia coli Strains Derived from Humans, Animals, and Meats

Abstract

Shiga toxin (Stx) can be classified into two types, Stx1 and Stx2, and different subtypes. Stx2e is a subtype commonly causing porcine edema disease and rarely reported in humans. The purpose of this study was to analyze the prevalence and genetic characteristics of Stx2e-producing Escherichia coli (Stx2e-STEC) strains from humans compared to strains from animals and meats in China. Stx2e-STEC strains were screened from our STEC collection, and whole-genome sequencing was performed to characterize their genetic features. Our study showed a wide distribution of Stx2e-STEC among diverse hosts and a higher proportion of Stx2e-STEC among human STEC strains in China. Three human Stx2e-STEC isolates belonged to O100:H30, Onovel26:H30, and O8:H9 serotypes and varied in genetic features. Human Stx2e-STECs phylogenetically clustered with animal- and food-derived strains. Stx2e-STEC strains from animals and meat showed multidrug resistance, while human strains were only resistant to azithromycin and tetracycline. Of note, a high proportion (55.9%) of Stx2e-STEC strains, including one human strain, carried the heat-stable and heat-labile enterotoxin-encoding genes st and lt, exhibiting a STEC/enterotoxigenic E. coli (ETEC) hybrid pathotype. Given that no distinct genetic feature was found in Stx2e-STEC strains from different sources, animal- and food-derived strains may pose the risk of causing human disease.

Phage Cocktail Targeting STEC O157:H7 Has Comparable Efficacy and Superior Recovery Compared with Enrofloxacin in an Enteric Murine Model

“…STEC O157:H7 is primarily found as part of the gut microbiota of cattle and is transmitted to humans through contaminated food, water, and direct contact with infected people or animals ( 2 ). It was reported that STEC isolates from animals and meat in China showed multidrug resistance ( 3 ). Vidovic et al ( 4 ) reported that 2% and 10% of STEC O157:H7 isolated from clinical and bovine samples, respectively, from western Canada were multidrug resistant.…”

Genomic Characterization of Escherichia coli O8 Strains Producing Shiga Toxin 2l Subtype

“…Therefore, we screened our STEC collection using the updated stx_subtyping database and identified five strains carrying the stx2l subtype, which was previously identified as stx2e based on the earlier nomenclature [7]. The sequence of transposable element IS2 was found among three of the five stx2l [17]. By searching the literature and publicly available sequences, several strains were found to carry the stx2l subtype, including the five meat-derived strains in this study, diarrheal patients-derived strains in Norway and Denmark [9], a human-derived strain in the UK, Roquefort cheese-derived strains in the USA [11], and sheep-derived strains in Ireland [15].…”

“…Identification of STEC strains carrying stx2l subtype (Stx2l-STEC) from our STEC collection was performed by an in-house stx_subtyping approach based on WGS data as previously described [16,17]. Briefly, an in-house stx_subtyping database was created including representative nucleotide sequences of all identified Stx1 and Stx2 subtypes.…”

Comparative Genomics of Shiga Toxin-Producing Escherichia coli Strains Isolated from Pediatric Patients with and without Hemolytic Uremic Syndrome from 2000 to 2016 in Finland

“…Three STEC strains carrying the heat-stable enterotoxin-encoding gene sta were distributed separately, indicating the genetic diversity of the STEC/ETEC hybrid. It is notable that serotypes of the three STEC/ETEC isolates (O187:H28, O100:H2O, and O2:H27) have been reported in STEC/ETEC hybrids previously (29)(30)(31), and STEC/ETEC hybrids are seemingly more likely to carry uncommon stx subtype, e.g., stx2e and stx2g, which is corroborated by this study (31). Further studies are required to investigate if STEC strains with certain genetic backbones more easily pick up exogenous genes, thereby facilitating the emergence of hybrid pathotypes.…”