Comparative Evaluation of Nested Polymerase Chain Reaction for Rapid Diagnosis of Human Brucellosis.

Brucellosis is recognized as a zoonotic disease with high morbidity in the absence of treatment. The primary diagnosis of brucellosis can be effective in the achievement of satisfying treatment results and prevention of chronic infections. The present study aimed to compare the efficiency of conventional microbiological and serological approaches with nested Polymerase chain reaction (nested PCR) for rapid diagnosis of human brucellosis. A total of 120 subjects with symptoms of brucellosis were included in the study. The sensitivity and specificity of nested PCR for the detection of Brucella bacteria were compared with serological and blood culture methods. Out of 120 patients enrolled, brucellosis was detected in 73 (60.83%) cases based on serological tests with a blood culture confirmation in 8.33% of participants. Based on the obtained results, 55% of cases were positive in serum agglutination test (SAT≥1:160), and Coombs (C-SAT≥1:160) tests. Furthermore, seven negative SAT cases were positive in C-SAT as evidence of chronic brucellosis. The results of the 2-mercaptoethanol (2-ME) ≥ 1:80 test were negative in six SAT-positive cases. Based on nested PCR results, 68.18% and 56.06% SAT positive samples were also detected by blood nested PCR and serum nested PCR, respectively. The sensitivity of blood nested PCR was significantly more than serum nested PCR, SAT≥1:160, and blood culture (p <0.001). Moreover, the specificity of blood and serum nested PCR was obtained at 100%, compared to blood culture and SAT≥ 1:160. In the present study, the nested PCR was able to identify chronic brucellosis in SAT negative patients. As evidenced by the obtained results, the nested PCR showed higher efficiency for rapid diagnosis of human brucellosis, as compared to the blood culture method. Furthermore, the findings pointed to the high performance of nested PCR for rapid diagnosis of both chronic and acute brucellosis.