Virulence of Yersinia enterocolitica determined by lethality in Mongolian gerbils and by the Serény test

Virulence of human and environmental strains of Yersinia enterocolitica was evaluated by lethality in Mongolian gerbils and by the Serény test. The inducement of conjunctivitis in guinea pigs and lethality in gerbils after intraperitoneal administration was restricted to a few serotypes of Y. enterocolitica. Human strains of serotype O:8 were the most virulent, whereas strains of the common human serotype O:3 and most others were essentially avirulent. One virulent strain of serotype O:8 produced fatal infections within 7 days in four of five gerbils receiving 100 cells intraperitoneally. There was no observable difference in virulence between intraperitoneal and oral routes of administration, and upon death the infecting strain was found in high numbers in heart blood, lung, liver, and spleen. Virulence in both guinea pigs and gerbils was related to the presence of VW antigen determined by a nutritional requirement for calcium.