Development and comparative evaluation of a competitive ELISA with rose bengal test and a commercial indirect ELISA for serological diagnosis of brucellosis.

The development of a competitive ELISA for the detection of brucella-specific antibodies in bovines is described. Anti-brucella guinea pig serum was used as a source of competing antibodies. Lipo-polysaccharide purified from inactivated B. abortus S19 culture was used as antigen for the development of the assay. Sera from cattle were used in the competitive ELISA, rose bengal test and a commercial indirect ELISA. The following cattle sera were tested: (i) known positive sera (n = 80) (ii) known negative sera (n = 100) and (iii) field sera (n = 1184). Based on the receiver operating characteristics curve analysis and frequency distribution of the percentage of inhibition, 30% inhibition was considered the cut-off for positive and negative results. The sensitivity and specificity estimate on comparison with the commercial indirect ELISA was 94.87 and 92.12% respectively. The competitive ELISA described is a simple method for the routine screening of animal sera for detecting Brucella-specific antibodies.