Detection of Brucella melitensis DNA in the milk of sheep after abortion by PCR assay

Laboratory diagnosis of brucellosis is generally performed by microbiological and serological methods. PCR assay is a specific and sensitive choice for the detection of different bacterial agents. An evaluation of this test was carried out for the detection of Brucella melitensis DNA in sheep milk. 102 milk samples from sheep after abortion were taken and studied using bacteriological culture, PCR and milk ring test (MRT). PCR found B. melitensis DNA in 24 (23.5%) out of 102 milk samples, while only 8 (7.8%) of the samples were positive to B. melitensis through direct culture. MRT found 28 (27.4%) positive milk samples. The detection limit for PCR in sheep milk inoculated with B. melitensis strain 16 M was 1.7 x 10(3) - 1.7 x 10(4) cfu/ml. PCR and MRT coincidence was 96%. The diagnostic sensitivity and specificity were determined as 100% and 81.3% respectively for PCR assay and 75% and 75% for MRT. PCR is a useful tool for a fast diagnosis of B. melitensis in sheep milk.