Do human-infecting Yersinia enterocolitica Isolates exhibit adaptive phenotypes?

Yersinia enterocolitica strains of biotype 4 (BT4) are the most prevalent in human cases in France, followed by biotype 2 (BT2). We evaluated four BT4 porcine (P) isolates and four BT2 bovine (B) isolates for their ability to survive at 4 °C in culture broth and on meat, exhibit motility at 4 °C and 12 °C, adhere to stainless steel at 12 °C, resist five biocides, and infect human intestinal Caco-2 cells. The objective was to determine whether animal isolates that genetically cluster with human (H) isolates (P+H+, B+H+) differ phenotypically from non-clustering isolates (P+H−, B+H−), based on core genome multi-locus sequence typing (cgMLST) using allelic distance thresholds of ≤5 for BT4 and ≤3 for BT2 isolates. No significant difference was observed for BT4 between P+H+ and P+H− isolates, nor for BT2 between B+H+ and B+H− isolates, for any test, except for motility. Porcine isolates clustering with human isolates (H+) exhibited a significantly reduced motility compared with non-clustering isolates (H−) (p-value < 0.05). In contrast, bovine isolates clustering with human isolates (H+) showed a significantly higher motility than non-clustering isolates (H−). Motility plays a role in the early stages of biofilm formation but is not directly involved in virulence, as Y. enterocolitica becomes non-motile at 37 °C. Animal isolates that did not cluster with human isolates displayed traits enabling their transmission along the food chain, suggesting potential low-level human exposure, asymptomatic carriage, or links to unreported infections.

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