Differentiation of serological responses to Yersinia enterocolitica serotype O9 and Brucella species by immunoblot or enzyme-linked immunosorbent assay using whole bacteria and Yersinia outer membrane proteins.

Serum samples from 134 patients showing by the microagglutination test serological cross-reactivity between Yersinia enterocolitica serotype O9 and Brucella spp. were analyzed by immunoblot and enzyme-linked immunosorbent assay techniques for the presence of antibodies directed against plasmid-encoded, yersinia-associated outer membrane proteins (OMPs). Since these OMPs are exclusively expressed in pathogenic strains of Yersinia spp., this characteristic was chosen for serological differentiation of infections caused by these bacteria. The presence of antibodies against plasmid-encoded OMPs of pathogenic Yersinia spp. in patient sera appeared to be a suitable means to identify acute or recent infection with Y. enterocolitica serotype O9, whereas the failure to detect such antibodies indicated an acute or recent infection with Brucella spp.