An enzyme-labelled immunosorbent assay for Brucella abortus antibodies.

An enzyme-linked immunosorbent assay (ELISA) for Brucella abortus antibody was compared with direct agglutination, complement fixation and Coombs tests in studies of 112 sera. Of these, 15 gave positive results by ELISA tests which included the 13 sera that gave positive results in the other tests. The assay aided recognition of four groups: (i) sera with very high levels of specific IgG and significant levels of IgM and IgA from patients with acute brucellosis; (ii) sera with high levels of IgG only from patients with chronic brucellosis; (iii) sera with low levels of IgG only, representing residual antibody; (iv) sera with little or no brucella-specific antibody. ELISA was antibody-class specific, and the results were more readily interpreted than conventional seological data. Moreover, ELISA was more sensitive, more rapid and simpler than the battery of agglutination, Coombs and complement-fixation tests commonly used.