ABSTRACT
After a first study on the serological behavior of Yersinia enterocolitica by W. Knapp and E. Thal in 1963, a provisional antigenic scheme was worked out by S. Winblad in 1967. Y. enterocolitica, like the other Enterobacteriaceae, possess lipopolysaccharide determinants corresponding to the O-antigen which are heat-stable and alcohol resistant. The study of the O-antigens of Y. enterocolitica is obstructed by the marked tendency of this organism to change to a rough form. The difficulties many workers met in typing Y. enterocolitica strains, particularly when using a heated antigen, can be explained, according to our experience, by the frequent presence of a partial R-antigen that is exposed by heating. Ahvonen et al. have drawn the attention on the strong cross-reaction existing between Y. enterocolitica type 9 and different Brucella species. In 1973, Rische et al. and W. Beer and G. Seltman studied the polysaccharide components of Y. enterocolitica.
