Human brucellosis: do we need to revise our therapeutic policy?

Objective: To identify risk factors of relapse among patients with osteoarticular brucellosis.

Methods: In a prospective cohort study, we investigated 90 patients with diagnosis of brucellosis, as established by clinical picture and at least 4-fold rise in antibody titer. Osteoarticular involvement was defined by inflammatory signs and radiographic changes. Thirty-five patients received combination therapy of 2 drugs (rifampicin + cotrimoxazole or doxycycline), while 55 patients received a combination of 3 drugs (streptomycin + rifampicin + doxycycline). Monthly followup comprised clinical and laboratory examinations (seroagglutination, IgG, IgM antibody titers). Recovery of patients was based on clinical improvement and seroagglutination antibody titer < or = 1:80, as well as negative results for IgG and IgM antibody titers. Incidence of relapse was recorded during the 2 year period of followup after finishing the course of treatment.

Results: All patients continued treatment beyond the usual 6 week period previously recommended. Relapse occurred in 59.3% in patients who received treatment for 5 months or less, while relapse occurred in 7.9% among those who received treatment for more than 5 months (p < 0.001). Sixty percent of patients who received combination therapy of 2 drugs had relapse, while there was no relapse in patients who received 3 drugs in combination (p < 0.001). Logistic regression analysis identified duration of treatment < 5 months and IgG level (above 50 U/ml) as independent predictors for relapse; the predictivity of the model was 85.6%.

Conclusion: Extending treatment for longer than previously recommended (6 weeks) resulted in an incidence of relapse significantly lower than for shorter courses of treatment. IgG antibody in addition to seroagglutinating antibody titers are useful for serological followup of patients with brucellosis.