[The background of the serological cross-reaction between Yersinia and Brucella and the possibility of differential diagnostics by the ELISA technique and the electroimmuno assay (rocket electrophoresis) (author's transl)].

A strong serological cross-reaction appears between different species of genus Brucella and Yersinia enterocolitica (Y.e.) serotype 0--9, which seriously complicates the diagnostic works of brucellosis and yersiniosis both in humans and animals. This cross-reaction makes it impossible to perform a differential serological diagnosis using common routine procedures such as the agglutination test and the complement fixation test. By the use of immunological, immunochemical and structural chemical methods it has been shown that the common antigenic structures of Brucella and Yersinia are situated in the lipopolysaccharides (LPS) of the cellwalls. In order to do structure analysis gaschromatography in combination with mass spectrometry of LPS from Brucella and Yersinia bacteria has been achieved. The results show that two monosaccharides (glucose and galactose) constitute common components of the LPS-molecules. A discovered cross-reaction between Y.e. 0--9 and Salmonella urbana (0--30) confirms the hypothesis that glucose and galactose are responsible for the serological cross-reaction between Brucella and Y.e. 0--9. An enzyme-linked immunosorbent assay (ELISA) has been developed in order to be used as a differential routine test. The results show that by using ELISA, a differentiation between antibodies against Y.e. 0--9 and B. abortus can be done with high sensitivity and accuracy. Another differential diagnostic system has been developed by the use of electroimmuno assay (rocket electrophoresis). This method raises the possibility of a rapid and a simple qualitative differentiation of antibodies against Brucella and Yersinia.