Evaluation of culture, tube agglutination, and PCR methods for the diagnosis of brucellosis in humans.

BACKGROUND: Brucellosis is prevalent in Saudi Arabia and Brucela melitensis is a leading cause of zoonosis worldwide. Therefore, accurate diagnosis of brucellosis is a key to its treatment and control. MATERIAL/METHODS: Twenty patients presented with symptoms of brucellosis were examined before and after antibiotic treatment for the diagnosis of brucellosis. Sequential blood samples collected monthly from each patient were tested for the diagnosis of brucellosis by serum plate agglutination test (SPA), standard tube agglutination test (STA), culture, and polymerase chain reaction (PCR). RESULTS: While most of the samples were positive by the agglutination tests, only 40% and 70% were positive by culture and PCR, respectively. After the course of antibiotic treatment, the culture rate and PCR results were positive in 10% of the samples. In contrast, anti-brucella antibodies of the treated patients were positive in 20% and 45% by STA and SPA tests, respectively. Furthermore, agglutinating antibodies in the presence of 2-mercaptoethanol were positive in 60% of the enrolled patients and negative in all patients after the antibiotic treatment. CONCLUSIONS: The present study revealed that the expression of anti-brucella antibodies does not correlate with the status of the disease condition. Further, completion of antibiotic therapy hampered the appearance of brucella-specific IgM antibodies, but did not eliminate the appearance of residual IgG antibodies in the treated patients. Therefore, for effective therapy, detection of the Brucella organisms by PCR or culture is an important attribute in the evaluation of the treatment regimen against brucellosis.