An Immunomagnetic Bead-Based Sandwich ELISA for the Detection of Brucella in Milk

Brucellosis is an important zoonotic disease caused by Brucella spp., posing significant impacts on animal health, livestock production, and public health. Infected dairy animals can shed the pathogen in milk, making milk a noninvasive and readily accessible sample for disease surveillance. Therefore, detection of Brucella in milk can be used for monitoring brucellosis in dairy herds. In this study, polyclonal antibodies were produced by immunizing camels with lipopolysaccharide (LPS) derived from Brucella abortus vaccine strain 19 (A19). These antibodies were subsequently conjugated to magnetic beads to develop immunomagnetic beads (IMBs). The IMBs were combined with a sandwich ELISA for the enrichment and detection of Brucella in milk samples. The IMB-sELISA showed a limit of detection (LOD) of 1 × 10⁴ CFU/mL. The method reduced matrix interference and showed satisfactory analytical performance. This approach can be applied for on-farm sample screening and herd-level surveillance to support the diagnosis and control of brucellosis in dairy animals.