Production of penicillin-specific polyclonal antibodies for a group-specific screening ELISA

Polyclonal penicillin-specific antibodies were obtained after the immunization of three rabbits with physiological penicillin-protein conjugates. The broad-specificity of the antisera was improved by alternate immunizations using immunogens with different penicillins as hapten. For the three antisera, the detection of ampicillin, amoxicillin, benzylpenicillin, oxacillin, cloxacillin and dicloxacillin was more sensitive in a competitive ELISA coated with the antibodies (antibody cELISA) compared to a competitive ELISA coated with a penicillin-protein conjugate (antigen cELISA). The detection of all penicillins in buffer solutions at concentrations below the MRL was achieved in the antibody cELISA when the penicillins were hydrolyzed with Penicillinase I. A simple extraction procedure was developed for the detection of penicillins in incurred porcine tissues using the antibody cELISA. Tissue fluids were used instead of the whole meat matrix, which simplified the sample preparation. Before analysis, the fluids were treated with kaolin to reduce the background signals in ELISA. The specificity, sensitivity, repeatability, decision limit (CC alpha) and detection capability (CC beta) were determined. The suitability of the antibody cELISA and the respective extraction procedure for screening purposes was demonstrated by comparison of the analysis of incurred samples using different screening assays. Almost 100% correlation (r=0.96) was found between the ELISA and a commercial immunochemical method, the Parallux (TM) assay.