Evaluation of B. melitensis whole-cell lysate antigen-based indirect ELISA for the serodiagnosis of caprine brucellosis

Different fractions of Brucella (B) abortus or Brucella melitensis have been used as antigens for the detection of anti-Brucella antibodies in goat sera, being their accomplishment cumbersome and time consuming. In an attempt to achieve a simpler enzyme-linked immunosorbent assay (ELISA) antigen preparation method for serodiagnosis of caprine brucellosis, we developed and evaluated a B. melitensis whole-cell lysate antigen-based indirect ELISA (Bm-WCL iELISA). A total of 162 serum samples from female crossbred goats collected from non-vaccinated herds against brucellosis were classified according to the buffered plate antigen (BPA) screening test and the complement fixation (CF) test and used for the indirect ELISA (iELISA) evaluation. The Bm-WCL iELISA showed a high Se and Sp [95.7% (CI 88.1% - 98.8%), and 92.4% (CI 83.4% - 96.7%), respectively] to detect the serological response against Brucella in commercial goat herds, and an almost perfect agreement with combined official tests results (κ = 0.88), when goat sera with concordant results in both official serological tests (BPA and CF; n = 136) were used. However, the agreement dropped to substantial (k > 0.73) when 26 goat serum samples with BPA and CF not concordant results were incorporated for the iELISA performance evaluation and the comparison was made for each test independently. Comparison of the Bm-WCL iELISA results with Brucella abortus sLPS iELISA showed almost perfect agreement (κ > 0.83). Even when a larger number of samples are needed to validate this test, these preliminary results encourage the optimization of the Brucella melitensis whole cell lysate antigen-based iELISA.