RESUMEN
Background: Brucellosis is a major zoonotic disease that is endemic in Saudi Arabia and it remains a major health problem that has not been eradicated in the country yet. Place and Duration of Study: This retrospective study was conducted in a Saudi Hospital at Al Madinah city during the period of 1 November, 2010 to 31 October, 2011. Methodology: All sera of patients suspected to have brucellosis (n= 65) and 18 healthy subjects were tested for brucella antibody using slide latex agglutination (SAT) and ELISA. Quantitation of IFN-ɣ was also done using ELISA. Results: Brucellosis was detected in all age groups but the incidence was higher and reached 33.3% in age group (40- <50) years with average of 43.9±2.53 years. Male to female ratio in infected patients was 2:1 by using SAT. The incidence of seropositive cases was high (80.1%) in the three months (April, May and June), with the highest peak in May (46.7%). Drinking raw milk was the most encountered risk factor with a prevalence of 66.1% followed by consumption of milk products (11.9%). The most prevalent species among the examined cases was B. melitensis (93.3%). Among the studied cases, 60 cases (92.3%) were serologically positive for brucellosis by SAT. Among the 60 cases yielding significant titers against brucella, 14 sera (23.3%) had agglutinin levels of 1:80, 34 sera (56.7%) had titers of 1:160 and 12 sera (20%) had titers of 1:320. By estimating IgM and IgG levels in the sera of examined cases using ELISA, 52 cases (80%) had brucellaIgM while 42 cases (64.6%) had brucella IgG. Sensitivities of SAT, IgM ELISA and IgG ELISA were 91.5%, 88.1% and 71.2%, respectively compared with combined ELISA. Mean IFN-ɣ levels ± SD in the subacute phase was 136.7±70.07pg/ml, 120.2±54.25pg/ml in the acute phase, and 121.3±51.09 pg/ml in the chronic phase of brucellosis. Conclusion: The sensitivity and specificity of ELISA to diagnose human brucellosis was higher when combined ELISA (IgM/IgG or both) was used. Mean IFN-ɣ levels were lower, but not significantly, in the chronic phase of the disease than in the sub acute phase and healthy subjects.