Comparison of the efficacy of polymerase chain reaction in the diagnosis of brucellosis by serological methods and detection of virulence genes

Aim: Brucellosis is a zoonotic infection that progress with multiorgan involvement. The classical diagnostic methods, including culture and serological tests, require long time to be completed and may yield false negative results. In this study, the performance of PCR, as a rapidly-developing method that is able to give results within hours, was aimed to be evaluated on the diagnosis of brucellosis. Material and Method: A total 60 patients and 60 control patients' samples which were assessed between January 1st, 2018 and July 31th, 2018 in our hospital were included. Brucella spp. DNA was investigated in the clinical samples with real-time PCR method, and species typing and virulence genes were studied with PCR. The diagnostic efficacy of PCR method was analyzed. Results: Brucella spp. growth occurred in eight of the patients' blood cultures. Fifty out of 60 patient samples which were found positive for antibody were determined as having ≥1/160 serum titer, and 32 of them having acute disease. Resting 18 patients were accepted as the patients who were currently under treatment. In the real-time PCR analysis, DNA of Brucella spp. were found positive in 19 samples in the patient group. Brucella melitensis were identified in all PCR-positive samples, and all these samples were also found positive for all the studied virulence genes including omp19, wbkA, manA, mviN, ure and perA. Of the PCR method, the sensitivity for patients group and acute patients were found as 31.6% and 59.3%, respectively; specificity and Positive Predictive values were determined as 100%, and Negative Predictive Value for acute patients was found as 87.1%. Conclusion: In this study, it was determined that Brucella PCR could diagnose almost 60% of acute patients, the specificity of this test was excellent, B. melitensis was the causative agent in all patients and all these strains were carrying all substantial virulence genes. It is concluded that more sensitive PCR kits having lower detection limit are required, and sampling from the patients in appropriate time will increase the efficacy of PCR in the diagnosis of brucellosis. Key Words: Brucella spp., Brucellosis, Serological Tests, PCR, Virulence.