Aim and Background. Brucella spp. is a gram negative coco bacillus which has different hosts including human, cow, sheep and goat. 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 determination of the hemi nested PCR technique sensitivity for detection of Brucella spp. in raw milk and cheese.

Materials and methods. In this study 15 raw milk samples, 15 pasteurized cheese samples and 15 traditional cheese samples were collected from Tehran and suburbs. DNA was extracted using DNP kit from samples. After optimization of first and second round of PCR, sensitivity and specificity of reactions were examined. Then all samples were tested using developed PCR.

Results. The PCR product which was obtained from first PCR round had 443 bp length, and the second round fragment had 225bp. The PCR sensitivity up to 100 particles was observed. Among 15 samples of raw milk, 10 cases were PCR positive. In 15 pasteurized cheese samples only 6 cases were PCR positive, and finally from 15 traditional cheese samples 8 were PCR positive.

Conclusion. With respect to this result, it could be said that in comparison with conventional detection technique for Brucella spp. diagnosis, PCR has a significant sensitivity and accuracy. Furthermore, it seems that using molecular detection technique as confirmative tests for detection of Brucella spp. is inevitable.