Research Project: MOLECULAR BIOLOGY AND GENOMICS OF FOODBORNE PATHOGENS
Location: Produce Safety and Microbiology Research
Title: The Olive Compound 4-Hydroxytyrosol Inactivates Staphyloccoccus aureus Bacteria and Staphylococcal Enterotoxin A (SEA)
Authors
Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 25, 2011
Publication Date: N/A
Interpretive Summary: Staphylococcus aureus is a major bacterial pathogen that develops resistance to medical antibiotics. It has been reported to cause clinical infections and contamination of a broad variety of foods, including canned mushroom, breaded chicken products, cheese, and raw milk as well on handles of shopping carts causing 185 000 cases of foodborne illnesses in the United States each year. Staphylococcus aureus produces the virulent staphylococcal enterotoxin A, a single chain protein which consists of 233 amino acid residues. It has been estimated that the toxin that is secreted by the bacteria is associated with 78% of staphylococcal outbreaks. The results of the present study show that the pure olive compound 4-hydroxytyrosol inactivated both Staphylococcus aureus pathogens and the toxin produced by these pathogens. A commercial organic olive powder donated by the producer, the CreAgri Company, Hayward, California, also inactivated the pathogens. However, because it was cytotoxic to the spleen cells used in the assay, it was not possible to separate the antimicrobial from the antitoxin effects. The described findings suggest that olive compounds have the potential to counteract adverse effects caused by Staphylococcus aureus bacteria and the virulent toxin produced by these pathogens. To our knowledge, this is the first report on the potential of a safe, edible plant compound to inactivate both pathogens and toxins. Technical Abstract: The foodborne pathogen Staphylococcus aureus produces the virulent staphylococcal enterotoxin A (SEA), a single chain protein which consists of 233 amino acid residues with a molecular weight of 27,078 Da. SEA is a superantigen that is reported to contribute to animal (mastitis) and human (emesis, diarrhea, atopic dermatitis, arthritis, toxic shock) syndromes. Changes of the native structural integrity may inactivate the toxin by preventing molecular interaction with cell membrane receptor sites of their host cells. In the present study, we evaluated the ability of the pure olive compound 4-hydroxytyrosol and a commercial olive powder called Hidrox-12 prepared by freeze-drying olive juice to inhibit S. aureus bacteria and SEA"s biological activity. Dilutions of both test substances inactivated the pathogens. Two independent cell assays (BrdU incorporation into newly synthesized DNA and glycyl-phenylalanyl-aminofluorocoumarin (GF-AFC) proteolysis) demonstrated that the olive compound also inactivated the biological activity of SEA at concentrations that were not toxic to the spleen cells as determined in the MTT assay. However, efforts to determine inhibition of the toxin by Hidrox-12 were not successful because the olive powder was cytotoxic to the spleen cells at concentrations found to be effective against the bacteria. The results suggest that food-compatible and safe anti-toxin olive compounds can be used to inactivate both pathogens and toxins produced by the pathogens.
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