Detection and analysis of Staphylococcal enterotoxin A in food by Western immunoblotting.
Western blotting has the potential to overcome some of the major problems associated with enzyme-linked immunosorbent assay (ELISA) detection of toxins in food, such as cross-reactivity with unrelated antigens and insensitivity with heat-treated foods, because the Western procedure solubilizes denatured protein and allows characterization of the antigen that reacts with the antibody. A simple Western immunoblotting protocol was developed to identify and measure the level of Staphylococcus aureus enterotoxin A (SEA) in food. Test samples are merely homogenized with no additional solubilization or pretreatment steps. The immunoblots detect SEA at levels as low as 100 pg/ml. Using the simplified sample preparation, both native and heat-denatured SEA were identified in a variety of foods including mushrooms, milk, potato salad and meat products. Our data suggest that SEA is being secreted at mid-log growth in BHI media as well as in mushrooms. These results suggest that Western blotting is a useful tool for determining the presence of SEA in foods because it allows characterization of the antigen reacting with the antibody and can be used for heat-treated foods, thus overcoming some of the limitations of the ELISA test.
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U.S. Food and Drug Administration, Division of Microbiological Studies, Washington, DC 20204, USA. Axr@vm.cfsan.fda.gov
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D000818:Animals; D015153:Blotting, Western / Q000379:methods*; D005516:Food Microbiology; D008461:Meat Products / Q000382:microbiology; D008892:Milk / Q000382:microbiology; D011198:Solanum tuberosum / Q000382:microbiology; D013205:Staphylococcal Protein A / Q000302:isolation & purification*; D013211:Staphylococcus aureus / Q000254:growth & development; D013997:Time Factors
D013205:Staphylococcal Protein A