The production and evaluation of a buffered plate antigen for use in a presumptive test for brucellosis.

A buffered Brucella plate antigen, pH 4.0, was developed for testing bovine and porcine sera which markedly reduced the number of "nonspecific" plate agglutination test reactions. Use of this antigen in a presumptive test decreased testing costs by lowering the amount of "nonspecific" reaction obtained on the standard plate agglutination test and reducing the use of the card test. The test is slightly more sensitive than the card test. Specificity and sensitivity were evaluated using sera collected from experimentally vaccinated and/or infected animals and from animals at slaughter. The antigen is currently being used in a presumptive test for brucellosis in the United States.