Abstract
Shiga toxin (Stx) is the key virulence factor in the Shiga Toxin-Producing Escherichia coli (STEC), which can cause diarrhea and hemorrhagic colitis with potential life-threatening complications. There are two major types of Stx: Stx1 and Stx2. Several Stx1/Stx2 subtypes have been identified in E. coli, varying in sequences, toxicity and host specificity. Here, we report a novel Stx2 subtype (designated Stx2m) from three clinical E. coli strains isolated from diarrheal patients and asymptomatic carriers in Sweden and Denmark. The Stx2m toxin was functional and exhibited cytotoxicity in vitro. The two Swedish Stx2m-producing strains belonged to the same serotype O148:H39 and Multilocus Sequencing Typing (MLST) Sequence Type (ST) 5825, while the Danish strain belonged to the O96:H19 serotype and ST99 type. Whole-genome sequencing (WGS) data analysis revealed that the three Stx2m-producing strains harbored additional virulence genes and the macrolide resistance gene mdf (A). Our findings expand the pool of Stx2 subtypes and highlight the clinical significance of emerging STEC variants. Given the clinical relevance of the Stx2m-producing strains, we propose to include Stx2m in epidemiological surveillance of STEC infections and clinical diagnosis.
Highlights
Phylogenetic trees (Figure 1. see Supplemental Material Figure S1 for extended version of this tree) demonstrated that the two unique Stx2 sequences from the three Shiga Toxin-Producing Escherichia coli (STEC) isolates form a distinct lineage from the described Stx2 subtypes and variants (Stx2a to Stx2l). These results suggest that the three STEC strains harbor a novel Stx2 subtype
Subtypes and variants (Stx2a to Stx2l)
Stx2a is frequently associated with a higher risk of Hemolytic UremicSyndrome (HUS) development, while Stx2e, Stx2f and Stx2g are present mainly in strains isolated from patients with uncomplicated diarrhea or non-human sources
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Shiga Toxin-Producing Escherichia coli (STEC) can cause various gastrointestinal diseases in humans, ranging from asymptomatic carriers to life-threatening Hemolytic Uremic. The major virulence factors of STEC are Shiga toxins 1 and 2 Stx is more heterogeneous and virulent than Stx, with Stx2a (with or without Stx2c) being considered more pathogenic to humans than other Stx subtypes [3]. Some rare human Stx subtypes, such as. We describe the identification of a novel Stx subtype from clinical. We performed whole-genome sequencing (WGS) to characterize the genomic features of the new Stx subtype and assess the Shiga toxin-production capability of the isolates
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