First description of aYersinia pseudotuberculosisclonal outbreak in France, confirmed using a new core genome multilocus sequence typing method

AbstractYersinia pseudotuberculosisis an enteric pathogen causing mild enteritis that can lead to mesenteric adenitis and septicemia in elderly patients. Most cases are sporadic, but outbreaks have already been described in different countries. We report for the first time aY. pseudotuberculosisclonal outbreak in France, that occurred in 2020. An epidemiological investigation pointed towards the consumption of tomatoes as the likely source of contamination. TheYersiniaNational Reference Laboratory (YNRL) developed a new cgMLST scheme with 1,921 genes specific toY. pseudotuberculosisthat identified the clustering of isolates associated to the outbreak and allowed to perform molecular typing in real time. In addition, this method allowed to retrospectively identify isolates belonging to this cluster from earlier in 2020. This method, which does not require specific bioinformatic skills, is now used systematically at the YNRL and proves to display an excellent discriminatory power and is available to the scientific community.