Aim and Background: Brucella spp. is a gram negative coco bacillus which has different hosts including human, cow, goat, sheep and horse. Brucella spp. is transferred via milk and dairy products causing a Malta fever in human. Serological methods for Brucella spp. detection do not have sufficient sensitivity and accuracy in addition, they have great false positive and negative results. The aim of this study is to assess the prevalence of Brucella spp. in dairy products with Nested PCR technique and evaluation of specification and sensitivity of this technique.

Material and methods: In this study 208 samples from dairy products including: 57 raw cow milk, 34 pasteurized cow milk, 28 pasteurized cheese, 23 traditional cheese, 33 raw goat milk and 33 raw sheep milk samples, were collected from Tehran and suburbs. DNA was extracted using DNP kit (Cinnagene, Iran) from samples. After optimization of first and second round of PCR for Nested, with the help of each specific primer, sensitivity and specificity technique was evaluated.

Results: The studies showed, Among 57 samples of raw cow milk, 19 cases were PCR positive. In 34 pasteurized milk samples 10 cases were PCR positive, from 28 pasteurized cheese samples only 8 cases, from 23 traditional cheese DNA samples 14 cases, out of 33 samples of raw goat milk 21 cases and finally from 33 samples of raw sheep milk 19 cases were PCR positive.

Conclusion: With respect to this result, Nested PCR technique investigated in this study, has significant sensitivity and accuracy therefore, the molecular technique as a confirmatory method in detection of Brucella spp. seems necessary and inevitable for serological methods.