Escherichia coli encoding Shiga toxin subtype Stx2f causing human infections in England, 2015–2022

Abstract

Introduction. Shiga toxin-producing Escherichia coli (STEC) belong to a diverse group of gastrointestinal pathogens defined by the presence of Shiga toxin genes (stx) of which there are at least ten subtypes (Stx1a-Stx1d and Stx2a-Stx2g). Gap Statement. Initially thought to be associated with mild symptoms, more recently STEC encoding stx2f have been isolated from cases of haemolytic uraemic syndrome (HUS) and the clinical significance and public health burden require further investigation. Aim. We analysed clinical outcomes and genome-sequencing data linked to patients infected with STEC encoding-stx2f in England to assess the risk to public health. Methodology. One hundred and twelve E. coli (n=58 isolates encoded stx2f; n=54 isolates E. coli belonging to CC122 or CC722 that had eae but were negative for stx) isolated from patients' faecal specimens between 2015 and 2022 were genome sequenced and linked to epidemiological and clinical outcome data. All isolates were investigated for the presence of virulence genes and a maximum-likelihood phylogeny of isolates belonging to CC122 and CC722 was constructed. Results. There were 52 cases infected with STEC harbouring stx2f between 2015 and 2022, with the majority identified in 2022. Most cases resided in the North of England (n=39/52, 75 %), were female (n=31, 59.6 %) and/or aged five and under (n=29, 55.8 %). Clinical outcome data were available for 40/52 cases (76.9 %) and 7/40(17.5 %) were diagnosed with STEC-HUS. In the two most common clonal complexes, CC122 and CC722, the presence of the stx2f-encoding prophage correlated with the presence of additional virulence genes, astA, bfpA and cdt, located on an 85kbp IncFIB plasmid. Conclusions. Certain serotypes of E. coli harbouring stx2f cause severe clinical outcomes, including STEC-HUS. Public health advice and possible interventions are limited, as little is known about the animal and environmental reservoirs and transmission routes. We recommend more comprehensive and standardized collection of microbiological and epidemiological data, and routine sharing of sequencing data between public health agencies worldwide.

Genomic analysis of an outbreak of Shiga toxin-producing Escherichia coli O183:H18 in the United Kingdom, 2023

“…The acquisition of stx appeared to correspond with the presence of the plasmid encoded virulence factors subA , ehxA , saa, and lpfA . As previously described, we considered the possibility that the stx -encoding phage may have been acquired on the plasmid and then subsequently incorporated onto the chromosome [ 46 ].…”

Genetic Diversity and Expression of Intimin in Escherichia albertii Isolated from Humans, Animals, and Food

“…Furthermore, each eae subtype possessed different genotypes. ρ/GT4 and α9/GT6 were associated with animal-derived strains that carried stx2f genes, which was relevant to clinical disease in finches and mild symptoms in humans [7,33].…”