Combined Immunomagnetic Separation and Detection ofSalmonella enteritidisin Food Samples

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Abstract
A model system for immunochemical detection of Salmonella enteritidis has been developed, using immunomagnetic separation (IMS) with both commercially‐available and laboratory‐prepared antibodies, followed by an enrichment stage and end‐point detection by ELISA. IMS alone gave an average of 77% recovery of cells artificially inoculated into the food, and a range of 20–110% recovery, depending on food type. The combined model system (IMS‐ELISA) enables detection of either < 10 cells m−1 whole egg extract (using overnight enrichment after IMS), or > 10 cells ml−1 (3 h enrichment after IMS). Cross‐reactivity of antibodies with Citrobacter was decreased by using two different immunochemical steps: IMS with monoclonal antibody‐coated beads, and a ‘sandwich’ ELISA with polyclonal capture antibody and monoclonal detector antibody. Discussion is presented on the best food preparation method, optimal substrate type for the ELISA and on the potential of IMS.