Introduction: The most common primers used to identify the genus Brucella are B4-B5 and F4- R2 that their targets are genes BCSP31 and 16S rRNA respectively. In clinical samples such as whole blood and serum, substances are present that inhibit DNA amplification and reduce the sensitivity of primers. The aim of this study was to evaluate and compare whole blood and serum samples in PCR for diagnosis of brucellosis by using primers B4-B5 and F4-R2. Material and Methods: 25 human blood samples and 25 serum related to them that were positive with serological tests, were collected in acute phase of brucellosis. DNA was isolated from blood samples using DNA extraction kit (Denazist Asia) and from serum samples by boiling method. DNA isolated from Serum samples were diluted 1/200. Then PCR were performed on blood and serum samples using the two primers. With each PCR, a positive control and a negative control was also set up. Finally, the sensitivity of these two primers for both blood and serum samples was evaluated. Result: From 25 whole blood samples which were tested by PCR, 19 samples (76%) with primer B4-B5 and 9 samples (36%) with primer F4-R2 were positive. From 25 serum samples, 21 samples (84%) with primer B4-B5 and 14 samples (56%) with primer F4-R2 were positive. Conclusion: In previous studies by the same researcher to evaluate different primers, primer F4- R2 had the highest sensitivity for diagnosis of brucellosis from purified bacteria. But by using blood and serum samples, PCR inhibitors affect on primers that reduce its sensitivity. Therefore for diagnosis of brucellosis from serum and blood, using the primers B4-B5 is preferred. Also with regard to DNA isolation from serum was boiling method, which has quality lesser than kit method, but use of serum instead of whole blood samples in detection of brucella is preferred.

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