Biochemical basis of the serological cross-reactions between Brucella abortus and Yersinia enterocolitica serotype O:9.

A method based on the inhibition of agglutination is described that may be used for the differential serological diagnosis between B. abortus and Y. enterocolitica serotype O:9. An antigen with high immunological capacity was isolated from Brucella. This antigen inhibited both homologous and heterologous agglutination by Brucella antiserum, but only the heterologous agglutination by Yersinia antiserum. It proved to be constitued of a polysaccharide (N-acetylglucosamine, glucose, mannose and 2-keto-3-deoxyoctonic acid), a protein and a phosphoglycerid moiety. Lipid A was absent from the Brucella antigen. Incomplete polysaccharide synthesis of the Brucella antigen, with concomitant loss of serological specificity by the rough mutant has been described. Oligosaccharides containing N-acetylgalactosamine, glucose and galactose were isolated from the specific side chain of Yersinia lipopolysaccharide. Lipid A constituents were also identified in the latter.