Separation and detection of salmonellae using immunomagnetic particles

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Abstract
Purified immunoglobulin G (IgG) raised against Salmonella typhimurium flagellin was coupled to a range of magnetic particles. Binding of cells to the immunomagnetic particles was quantified using a bioluminescence technique. Based on the results obtained, Dynabeads were selected for further study. Various factors including the bacterial growth medium and the time and temperature of incubation affected cell binding. A 10 min incubation at ambient temperature was selected to maximise immunological binding and to minimise non‐specific interactions. Using these optimised separation parameters, S. typhimurium was enriched from a range of mixed cultures by between 3‐ and 2,700‐fold. Several commercially available genus‐specific Salmonella antisera were coupled to Dynabeads and screened for efficacy of cell binding. The optimum immunomagnetic particle system was used to separate viable Salmonella enteritidis from artificially contaminated egg yolk and detected down to a level of about 105 cfu.g‐1 in 20 min using the firefly bioluminescent assay. Further applications of the immunomagnetic particle technique are discussed.