Serum specimens
Bovine whole blood (for serum) was obtained by collecting jugular venous
blood into glass tubes during routine brucellosis surveillance in
Armenia. Serum was transferred into separate tubes and tested by rose
bengal test (RBT). Positive samples were confirmed by complement
fixation test (CFT) and enzyme-linked immunosorbent assays (ELISA), and
stored at -20oC. Several negative and positive sera
were pooled together to produce negative and positive batches. In order
to limit the risk of bacterial contamination, all the sera used were
filtered through 0.22µm PVDF low protein binding filter (Millipore,
Sigma) before the preparatory step. Pooled serum was tested by RBT
before and after filtration.