Serum is the preferred clinical specimen for diagnosis of human brucellosis by PCR.

Human brucellosis poses a significant public health problem in many developing countries and requires fast and accurate diagnosis. A PCR assay amplifying part of the 31-kDa Brucella abortus antigenic protein gene sequence was developed and applied to whole-blood and serum samples from 31 brucellosis patients and 45 healthy individuals. All patients except one had detectable Brucella DNA in either whole blood or serum (combined sensitivity, 97%), but the assay sensitivity was higher with serum samples (94%) than with whole-blood samples (61%). The assay specificity was excellent (100%). A confirmatory PCR assay targeting another Brucella gene region (omp-2) was also developed but lacked sensitivity. Serum is the optimal specimen for the diagnosis of brucellosis by PCR, a choice that leads to assay simplification and shortens turnaround time.