Observations on serological cross-reactions between smooth Brucella species and organisms of other genera.

Serological cross-reactions have been demonstrated between smooth Brucella species and Escherichia coli 0:116 and 0:157, Salmonella serotypes of Kauffmann-White group N, Pseudomonas maltophilia and Yersinia enterocolitica 0:9 and 0:16. All of these organisms may evoke significant titres of cross-reacting antibodies in cattle and pigs inoculated by parenteral routes. E. coli 0:157, Salmonella urbana and Y. enterocolitica 0:9 evoked substantial titres of cross-reacting antibodies in cattle inoculated by the oral route with live organisms. Only Y. enterocolitica 0:9 was effective in evoking cross-reacting antibodies to Brucella in pigs inoculated by the same route. Differentiation of cross-reacting and homologous antibodies to Brucella was difficult and was not accomplished consistently by any single test.