External factors influence intrinsic differences in Stx2e production by Porcine Shiga Toxin-producing Escherichia coli strains

Authors: VAN HOORDE, SANDER - Ghent University; VEREECKE, NICK - Ghent University; SPERLING, DANIEL - Ceva Animal Health; He, Xiaohua; COX, ERIC - Ghent University; DEVRIENDT, BERT - Ghent University

Submitted to: PLoS Pathogens
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/12/2025
Publication Date: 10/22/2025
Citation: Van Hoorde, S., Vereecke, N., Sperling, D., He, X., Cox, E., Devriendt, B. 2025. External factors influence intrinsic differences in Stx2e production by Porcine Shiga Toxin-producing Escherichia coli strains. PLoS Pathogens. 21(10): e1013616. https://doi.org/10.1371/journal.ppat.1013616.
DOI: https://doi.org/10.1371/journal.ppat.1013616

Interpretive Summary: Most animals only represent asymptomatic carriers of STEC, however, post weaning pigs are susceptible to Stx2e produced by E. coli. This study aimed to understand which external and intrinsic factors might influence Stx2e secretion of porcine STEC field strains. Significant variations in Stx2e production among strains were observed, with bile acids and antibiotics exerting strain-specific effects on toxin secretion. While deoxycholate emerged as a key modulator of Stx2e production, the underlying genetic factors contributing to strain variability remain to be fully elucidated. Our findings underscore the need for further genome sequencing and analysis to identify genetic determinants associated with Stx2e secretion levels. Moreover, the presence of a holin gene in certain strains appears to enhance Stx2e secretion, suggesting a potential role in toxin secretion regulation.

Technical Abstract: Porcine Shiga toxin-producing Escherichia coli (STEC) strains pose significant challenges to the pig industry. The toxins produced by these strains, particularly Shiga toxin subtype 2e (Stx2e), are associated with a range of clinical symptoms such as diarrhoea and oedema disease, which in severe cases result in death. Understanding the factors that influence the production and secretion of Stx2e is crucial to elucidate porcine STEC pathogenesis and to develop effective therapeutic strategies. Therefore, this study aimed to characterize the variability in Stx2e production and secretion among different porcine STEC strains and assess the effect of several external factors, including bile acids and antibiotics. Our results highlighted substantial variability of Stx2e secretion from porcine STEC strains. Bile acids exerted strain-specific effects on Stx2e secretion, with deoxycholate significantly modulating toxin production. Antibiotics also affected Stx2e secretion with ciprofloxacin and enrofloxacin inducing a substantial increase in toxin production in certain strains. Genome analysis revealed that these strains encode a holin gene downstream of the Stx2e operon. Deleting this holin gene abolished antibiotic-induced increase in Stx2e secretion, while holin supplementation increased Stx2e secretion even further. These findings unravel a role for holin in Stx2e secretion and highlight the intricate interplay between genetic and environmental factors in regulating Stx2e production in porcine STEC strains. Together, they offer insights into STEC pathogenesis and open avenues for potential new therapeutics.