Brucellosis relapse: Rate, patient characteristics, and clinical outcomes in an endemic region

Brucellosis is the most common zoonotic disease worldwide, with significant heterogeneity in the literature regarding the risk factors and rate of relapse, we reviewed cases of confirmed brucellosis in Saudi Arabia, looking at the rate of relapse, characteristics of relapse cases, and compared it to the existing literature.

A retrospective analysis was conducted on confirmed cases of brucellosis. Cases with suspected relapse, as noted in medical charts, were identified. A detailed review of clinical and laboratory findings, along with associated outcomes, was performed to confirm instances of brucellosis relapse. Descriptive analysis was then undertaken to characterize confirmed relapse cases.

Of the 1,049 confirmed brucellosis cases over eight years, 73 cases were initially suspected of potential relapse. After excluding misdiagnosis and repeat exposures cases, there were 37 cases confirmed as relapses, resulting in a relapse rate of 3.53%. When considering only cases where patients adhered to the full treatment regimen, 10 patients were considered as "true relapse" cases, reducing the relapse rate to 0.95%. Among the 10 true relapse cases, four initially presented with bacteremia, and all ten patients had elevated Brucella titers. None had focal infection initially. All true relapse patients received Doxycycline as the core agent, with rifampin or streptomycin as a second agent. Upon relapse, four patients developed spondylitis, and three had bacteremia. Eight patients received an extended duration and/or triple therapy, and only one patient relapsed for a third time with an infected cardiac device. No mortalities were recorded within 90 days of completing relapse treatment.

The relapse rate observed in this study is lower than previously reported in the literature. Further research on brucellosis relapse should prioritize investigating treatment adherence and establishing a standardized definition, which might help address the current discrepancies in reported data.