Genome based characterization of Yersinia enterocolitica from different food matrices in Switzerland in 2024.

Yersinia enterocolitica causes food-borne gastroenteritis. However, little is known about the genetic diversity and pathogenic potential of Y. enterocolitica in different food commodities. In this study, presumptive Y. enterocolitica strains were isolated from 32 of 100 pork samples, from 25 of 100 chicken meat samples, and from 22 of 97 produce samples (fresh herbs and salads), all collected at retail level in Switzerland in 2024. All isolates underwent whole-genome sequencing (WGS). One isolate was re-classified as Y. hibernica. Three strains belonged to biotype (BT) 4, all from pork, and 86 strains to BT 1A. The isolates belonged to 45 sequence types (STs). A total of 76 putative plasmids were detected. Each BT 4 isolate carried a pYV-like plasmid harbouring 44 virulence factors (VFs). Plasmids from the same type were identified in different ST, showing that genetic exchange between ST occurs. Twelve isolates from poultry meat carried plasmids harbouring the msrAB operon which is linked to oxidative stress tolerance. Nine isolates from pork and poultry meat contained plasmids carrying the cag pathogenicity island associated with cytotoxicity, and four isolates from produce carried plasmids harbouring a heat labile enterotoxin. None of the isolates harboured plasmid-mediated antimicrobial resistance (AMR) genes. Y. enterocolitica BT 4 (n = 3) and BT 1A (n = 3) were clonal to Y. enterocolitica previously isolated from Swiss human cases. Our data provide valuable insights into the occurrence and genomic characteristics of Y. enterocolitica in food, their relatedness to human strains, and their adaptation to food matrices.