Prevalence of Shiga toxin producing Escherichia coli (STEC) in wild reservoir species in the Republic of Ireland

Abstract Background Shiga toxin-producing Escherichia coli (STEC) are a frequent cause of food poisoning and haemolytic uremic syndrome (HUS). An increasing number of STEC outbreaks is linked to fruit and vegetables contaminated by faeces from birds and mammals, yet screening in wildlife is limited. Results This study determined the prevalence and potential virulence of STEC from wildlife sentinel species in Ireland: herring gulls ( Larus argentatus ), lesser black-backed gulls ( Larus fuscus ) and hybrid deer ( Cervus elaphus x Cervus nippon ). These species were selected as they operate at the interface between humans and wildlife in urban ecosystems (herring gull) and rural ecosystems (deer), while lesser black-backed gulls can be found in both. STEC were isolated from deposited faecal specimens, identified by qPCR for detection of stx1 , stx2 , stx2f and eae genes, followed by DNA sequencing for confirmation and identification of antimicrobial resistance, virulence and stress genes. STEC were found in 1/132 (0.8%) of herring gull, 10/140 (7.1%) of lesser black-backed gull and 21/145 (14.5%) of hybrid deer samples. Following sequencing, 22/29 isolates were confirmed as STEC. Eight Shiga-toxin variants were identified, with stx1c and stx2b most common, both found in nine (31%) of the isolates. A single STEC from herring gulls (HO-195) harboured stx2f , which is the first stx2f -positive isolate found in this species. HO-195 was genotypically resistant to copper, tellurium, beta-lactams and fosfomycin, and encoded the most virulence genes among all the isolates. Conclusion These findings suggest wildlife may acquire STEC from livestock, highlighting the need for enhanced farm and wildlife surveillance. Understanding where these bacteria occur in nature is crucial for designing better surveillance and prevention strategies to protect public health.