Role of Yersinia enterocolitica Yst toxin in experimental infection of young rabbits.

We constructed a Yst-negative mutant of Yersinia enterocolitica W1024 by reverse genetics, and we compared the virulence of the yst+ and yst isogenic strains in an experimental oral infection of the young rabbit. The rabbits infected with the yst+ strain suffered from the diarrhea and lost weight, and most of them died. By contrast, the occurrence of diarrhea, weight loss, and death in the group of rabbits infected with the yst mutant was as low as that in the group of uninfected rabbits. Bacteria from both strains were excreted in the feces and induced a serum antibody response against Yop proteins. The yst mutant disappeared more rapidly from the feces. We conclude that the enterotoxin Yst is a major factor involved in the Y. enterocolitica-associated diarrhea in the young rabbit. Given the similarity with the symptoms observed for children, this result suggests that Yst could also be an important factor in diarrhea in young children infected with Y. enterocolitica.