We report three cases of mycotic aortic aneurysms due to Yersinia enterocolitica. In all cases, serogroups are O:9. The three patients more than 70 year-old men with immunodeficiency underlying conditions allowing bacterial graft (neoplasia, diabetes mellitus, dysimmunitary syndrome, hematologic diseases). The six cases of the literature were clinically, biologically and epidemiologically similar. The strains of Y enterocolitica responsible for septicemia are especially serogroups O:9. This is probably due to particular virulence factors in this serogroup (phagocytosis resistance gene: yopH, ypkA et yop E) (yop: Yersinia outer membrane proteins). The presence of a pYV plasmid (plasmid yersinia virulence), found in Yersinia pathogen strains, lead to bacterial proliferation in the tissues. The authors discuss pathophysiological mechanisms involved in arterial bacterial graft following an Y. enterocolitica infection.