Combined serology and antibiotic residue detection in a Luminex assay

Serum of slaughter pigs is being used for routine testing of antibodies against pathogens and can also be used for detection of antibiotic residues. Since the assay formats differ (direct detection of antibodies vs. inhibition assays for residues), these tests are performed in parallel, not in a multiplex set-up. For this study, a protocol for testing both antibodies and residues in one sample was investigated using the dedicated multiplex xMAP platform of Luminex. The results suggest that direct detection of antibodies combined with an inhibition assay for antibiotic residues is possible. Although the required sensitivities are not yet met, the results are promising and further optimizations to successfully combine the two detection methods in one multiplex assay are ongoing. Introduction Slaughter pigs are tested for several types of hazards, such as zoonotic pathogens like Salmonella or Trichinella and antibiotic residues. Pathogen detection can be done by the detection of serum antibodies with immunoassays like ELISA. For the detection of antibiotic residues, a microbial inhibition test in renal pelvis fluid (pre-urine) is being used. As a faster alternative, these (small) residues can also be detected in serum with an immunoassay, i.e. an inhibition test. The purpose of the research described here is to combine these different assay principles (Fig. 1) in one protocol using the bead-based multiplex technology of Luminex. Figure 1 Assay principles. For each type of assay Luminex beads are depicted that are either conjugated with sulfonamide (top) or Trichinella antigen (bottom). All ingredients required for the respective assays are described in the legend. Abbreviations: PE: phycoerythrin.