A competitive enzyme immunoassay for detection ofSalmonellasp. was developed in order to provide a sensitive assay for same‐day identification ofSalmonellasp. the assay could be performed in about 90 min and consisted of the following steps. Lipopolysaccharide derived fromSalmonella typhimuriumwas used to passively coat polystyrene 96‐well plates and tubes. A titrated amount of monoclonal antibody specific for an outer lipopolysaccharide core epitope commonly found inSalmoneilasp. was mixed with the prepared test sample prior to adding the mixture to the antigen coated matrix. Antibody bound to the immobilized antigen was detected with horseradish peroxidase labelled goat antimouse IgG (H&L chain).The analytical sensitivity of the assay was 3.1 ng and 5.6 ng of lipopolysac‐charide per ml for the plate and tube formats, respectively, if 25% inhibition or less was considered negative. This cutoff level was based on reactivity of unrelated monoclonal antibodies withS. typhimuriumlipopolysaccharide and lipopolysac‐charide fromE. coliwith theSalmonellaspecific monoclonal antibody in th
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