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Cyril Savi, Institut Pasteur, Paris : Circulation, evolution and genetic diversity of Yersinia pseudotuberculosis
Yersinia pseudotuberculosis (Ypstb) is a pathogen of the gastrointestinal tract, closely related to Y. pestis, the plague agent. The population structure of Ypstb has been determined using a cgMLST developed in the Yersinia National Reference Laboratory. The population is composed by 155 different genotypes. The epidemiology study of these genotypes revealed that some are restricted to a specific geographical area whereas others are spread worldwide. Two genotypes (1 and 8) are associated with a peculiar form of infection (Far east scarlet-like fever) and two others (5 and 6) are associated with an invasive form of infection, suggesting higher virulence. Phylogenetic analysis showed that Y. pestis represents a genotype of Ypstb, and that genotype 5 is its closest relative. Spatial and temporal diffusion study of Ypstb revealed that this species emerged in Asia before reaching Europe, where it started to spread worldwide. The evolution study of the species revealed that different processes (gene acquisition/loss, SNP, insertion sequences) led to the emergence of diverse genotypes with differential virulence potential.