Background: Brucellosis is prevalent in Saudi Arabia and Brucella melitensisis a leading cause of zoonosis worldwide. Therefore, accurate diagnosis of brucellosis is a key to itstreatment and control. Material/Methods: Twenty patients presented with symptoms of brucellosis wereexamined before and after antibiotic treatment for the diagnosis of brucellosis. Sequential blood samplescollected monthly from each patient were tested for the diagnosis of brucellosis by serum plate agglutinationtest (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 byculture and PCR, respectively. After the course of antibiotic treatment, the culture rate and PCR resultswere positive in 10% of the samples. In contrast, anti-brucella antibodies of the treated patients werepositive in 20% and 45% by STA and SPA tests, respectively. Furthermore, agglutinating antibodies inthe presence of 2-mercaptoethanol were positive in 60% of the enrolled patients and negative in all patientsafter the antibiotic treatment. Conclusions: The present study revealed that the expression of anti-brucellaantibodies does not correlate with the status of the disease condition. Further, completion of antibiotictherapy hampered the appearance of brucella-specific IgM antibodies, but did not eliminate the appearanceof residual IgG antibodies in the treated patients. Therefore, for effective therapy, detection of theBrucella organisms by PCR or culture is an important attribute in the evaluation of the treatment regimenagainst brucellosis.

Keywords: Adolescent, Antibodies, Bacterial - blood, Antigens, Bacterial - genetics, Brucella melitensis - isolation & purification, Brucellosis - diagnosis, DNA, Bacterial - blood, Hemagglutination Tests, Polymerase Chain Reaction