Chronic brucellosis and persistence of Brucella melitensis DNA

After acute brucellosis infection, symptoms persist in a minority of patients for more than 1 year. Such patients are defined as having chronic brucellosis. Since no objective laboratory methods exist to confirm the presence of chronic disease, these patients suffer delays in both diagnosis and treatment. The aim of the current study was to evaluate the usefulness of quantitative real-time PCR (Q-PCR) in the diagnosis and follow-up of these patients. Thirty-five subjects with a well-documented history of brucellosis that had been diagnosed between 2 and 33 years previously were screened by Q-PCR for the presence of Brucella melitensis DNA and by serological tests and blood culture. Subjects were divided into three groups: 8 (23%) focal-disease subjects, 9 (26%) nonfocal-disease subjects with subjective complaints, such as fatigue, malaise, arthralgia, and/or myalgia, and 18 (51%) asymptomatic subjects. All (100%) focal-disease patients and symptomatic nonfocal-disease patients had at least one positive Q-PCR sample. Only six (33%) of the asymptomatic subjects had Q-PCR-positive samples (P < 0.05). Eleven patients (five focal-disease patients and six nonfocal-disease patients with subjective complaints) received therapy during the study. For those patients who completed treatment, six (60%) still had Q-PCR-positive samples at the posttreatment follow-up. The proportion of individuals with B. melitensis DNA was significantly higher for symptomatic nonfocal-disease patients than for asymptomatic subjects. Therefore, Q-PCR appears to be a useful method for identifying chronic brucellosis patients.