Isolation and identification of Brucella in two dairies and comparison of four serological tests.

Four kinds of serological tests, i.e. rose bengal plane test (RBT), standard agglutination test (SAT), indirect enzyme linked immunosorbent assay (iELISA) and competitive enzyme linked immunosorbent assay (cELISA) were used to detect the presence of Brucella in 600 dairy milk cows from two dairies in east China and Xinjiang area. And 120 milk samples taken from the dairy milk cows with positive serological reactions to Brucella infection were selected to perform the isolation of the etiological agents and their identification by means of Gram and Kozlowski staining as well as PCR assay. With these methods of testing, 17 strains of Brucella abortus were isolated in these two dairies with an average positive rate of 14.17%, while the average positive rates of the 4 serological tests, RBT, SAT, iELISA and cELISA were 46.33%, 41.00%, 48.17% and 40.50% respectively. Meanwhile, the sensitivities and specificities of RBT, SAT, iELISA and cELISA tests were 86.36% and 85.71%, 84.09% and 92.06%, 86.36% and 96.83%, 95.45% and 98.41% respectively. It is evident that the sensitivities and specificities of iELISA and cELISA are higher than those of RBT and SAT test , and these two methods can be used as alterative method of testing for Brucella in cow milk to replace the RBT and SAT tests usually used in the detection of Brucella.