Comparison of the tests polymerase chain reaction, serology, and blood culture with respect to sensitivity and specificity for detection of Brucella spp in human samples

The aim of this study was to evaluate the sensitivity and specificity of polymerase chain reaction for detection of Brucella spp in human blood samples compared with the serological tests and blood culture. In 2005, a total of 92 people were sampled from the towns of Anahuac and Sabinas Hidalgo, Nuevo Leon, where an outbreak of human cases had taken place in the same year as this study. The sera collected were analyzed by serological tests according to the NOM 022-SS2-1994. DNA was obtained using CTAB extraction method and it was used to amplify a fragment of 223 bp of the coding sequence for a protein of 31 kDa present in all Brucella species. The polymerase chain reaction test detected 23 positive samples. The sensitivity and specificity compared with RB was 44.68 and 95.56%, respectively. Compared with mouse antibody production, it was 51.61 and 88.52%, and 2-mercaptoethanol was 53.57 and 87.50%. When isolation (positives cultures) was compared with polymerase chain reaction, we obtained 100.0% sensitivity and 80.23% specificity, taking into account people with positive and negative serology. The polymerase chain reaction test can be an alternative tool to bacterial culture in human brucellosis diagnosis.