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Chapter 9 : Staphylococcus aureus
Category: Applied and Industrial Microbiology; Food Microbiology
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Although there is an obvious advantage to a pathogen that can disrupt the host immune system, there is a gap in knowledge as to the exact etiology of the disease. First, Staphylococcus aureus that harbors enterotoxin genes was determined to reside in the healthy gut of more than 50% of the nonenteritis-associated patients examined in a recent study, suggesting that the pathogenicity is dictated in part by "to be determined" host factors that lead to pathogen spread and heavy enterotoxin production. Second, there is a lack of evidence for the exact origin of symptoms. There are over 20 known staphylococcal proteins that share high similarity to the staphylococcal enterotoxins (SEs). The SEs have classically been organized into families based on their percentage identity or similarity. Methicillin-resistant S. aureus (MRSA) was first identified in food-producing animals in the 1970s, being identified as a cause of mastitis in dairy cattle. A logical extension of concerns regarding MRSA in food animals was investigation of MRSA contamination of food products. There are three main areas of concern relating to the potential routes of transmission: MRSA as a cause of classical enterotoxin-associated food poisoning, contaminated food as a source of nasal colonization, and contaminated food as a source of extraintestinal infection. Nasal passages are the most common site of MRSA colonization in humans, and the nose is a frequent hand-contact site. Good food handling and hygiene practices could minimize the risks for food handlers.
Phylogram of SE proteins. Signal sequences were not included in the analysis. The phylogram was generated at the European Bioinformatics Institute (EBI), part of the European Molecular Biology Laboratory (EMBL) (http://www.ebi.ac.uk/Tools/clustalw2/).
SE protein properties and genetic location a