Detection of Escherichia coli O157:H7 in meat by an enzyme-linked immunosorbent assay, EHEC-Tek.

Investigation of the specificity of an enzyme-linked immunosorbent assay (ELISA) for detection of Escherichia coli O157:H7 in raw meats (EHEC-Tek; Organon Teknika Corp.) revealed that the target antigens of the detection reagent, monoclonal antibody 4E8C12, were present in numerous serotypes of E. coli and that their ELISA reactivity was influenced by bile salts, acriflavine, and heat. The specificity of the ELISA was improved by a modified test protocol incorporating immunocapture.

Monoclonal antibodies which identify a genus-specific Listeria antigen.

Fifteen murine monoclonal antibodies (MAbs) which react specifically with a protein antigen found in all species of Listeria were developed and characterized. These MAbs were tested extensively by both enzyme-linked immunosorbent assay and Western blot (immunoblot) analyses for cross-reaction with non-Listeria organisms, such as Staphylococcus, Streptococcus, Citrobacter, Pseudomonas, and Salmonella species, and were found to be nonreactive. The genus-specific antigen was identified as a heat-stable protein with a molecular weight in the range of 30,000 to 38,000 (under both reducing and nonreducing conditions), depending on the species of Listeria tested. In Listeria monocytogenes, L. innocua, L. ivanovii, and L. seeligeri the antigen has a molecular weight of approximately 30,000 to 34,000. In L. grayi and L. murrayi it has a molecular weight of approximately 35,000 to 38,000. In addition, several of the MAbs recognize lower-molecular-weight protein bands. There appear to be at least two groups of Listeria-specific MAbs based upon isotype and results of enzyme-linked immunosorbent assay and Western blot analyses. These MAbs have proven to be useful in the development of a diagnostic assay for Listeria species in food products.

Rapid monoclonal antibody-based enzyme-linked immunosorbent assay for detection of Listeria in food products.

A rapid diagnostic test for the detection of Listeria in food products has been created. This test, known as Listeria-Tek, uses 2 monoclonal antibodies specific for Listeria in an enzyme-linked immunosorbent assay (ELISA) format. The test requires only 40 h of broth enrichment with no culturing on solid media. It is extremely simple to perform and easy to interpret, and is at least as sensitive and accurate as the best of the culture methods. The test can be used with dairy products, meat products, and environmental samples. The ELISA test is safely performed on the open bench of the laboratory because no live cultures, no radioactivity, no phage, etc., are necessary. There is no need for special licenses or reserved laboratory space, and no waste disposal problems are encountered. If necessary, one technician could easily perform hundreds of assays per day. A printed data sheet is available for permanent records.