Shiga toxin-producing Escherichia coli in retail foods in Poland: occurrence and genetic diversity

The aim of this study was to determine the prevalence of Shiga toxin - producing Escherichia coli (STEC) in food samples from retail markets in Poland and to explore their pathogenic potential. The prevalence of STEC in food products was tested in the years 2016–2020. Among 8,425 food samples including vegetables within sprouts and meat products, 44 STEC strains were isolated. The prevalence of STEC was very low, only 0.52% in the years studied. The most common virulence profile was stx2+ (n = 31), stx1 +, eae+ (n=5), stx1 + , stx2+ (n= 3), stx1 +, stx2+, eae+ (n=5) and eae+ (n=10) Based on the cgMLST analysis the 17 isolates were differentiated into 14 sequence types (ST) and in 8 clonal complexes (CC). Thirteen serogroups and one undefined serogroup were found among the strains tested among them there. There were also strains belonging to the five main serological groups O26, O103, O111, O145, and O157. The most frequently observed resistance phenotypes were observed to amoxicillin-clavulanic acid (15%), and cefuroxime sodium (7%). Our study identified two hybrid-pathogenic strains of E. coli , 3456 and 5076, virulence characteristics associated with multiple pathotypes. Strain 3456 combines characteristics of enterohemorrhagic E. coli (EHEC) and extraintestinal pathogenic E. coli (ExPEC). Strain 5076 is a hybrid of STEC and ExPEC. These hybrid strains pose a serious threat to public health due to their potential to cause enteric and extraintestinal infections and their association with serious clinical outcomes. • STEC was found in 0.52% of 8,425 retail food samples in Poland (2016–2020) • 44 STEC strains were isolated; stx2+ was the most frequent virulence gene • cgMLST identified 14 sequence types and 8 clonal complexes • Detected serogroups included O26, O103, O111, O145, O157 • Two hybrid STEC/ExPEC E. coli strains were found