Lecture%209

Lecture%209 - Viruses Viruses Much less is known about the...

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Viruses
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Viruses Much less is known about the incidence of viruses in food Obligate parasites, therefore do not grow on culture media Tissue culture and chick embryo techniques Viruses do not replicate in food Numbers expected to be low relative to bacteria Extraction and concentration necessary for recovery Any food can serve as a vehicle for virus transmission Viral gastroenteritis is second only to common cold frequency
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Incidence in food and environment Most common food source: shellfish Molluskan shellfish (filter feeders) No relationship between coliforms and viruses Persist in ground beef None found in vegetable samples tested Failed to survive on surface of fruits None found in vegetable processing plant Market foods examined Conclusion: viruses in US food supply are very low
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Food and Water-borne Viral Disease Viruses are not cells Reproduce inside cells, and rely on cell metabolism to supply their needs Disrupt host cell functions and cause symptoms very similar to those produced by bacteria attacking the same host cells There are viruses that infect intestinal cells and cause gastroenteritis symptoms No different than symptoms of staphylococcal enterotoxin attaching to intestinal cells
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Food and Water-borne Viral Disease Viruses that pass through the intestines and cause damage in liver Symptoms similar to those caused by bacteria attacking the same organs Major differences between bacterial and viral diseases Differences between the two kinds of microbes
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Properties shared by all food-borne viruses A. Food-borne viruses grow only inside host cells, very host specific: Most viruses which infect humans are found only in humans Viruses that infect intestinal cells unable to multiply elsewhere in the host Lab: viruses must be cultured in cell tissue cultures
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Lecture%209 - Viruses Viruses Much less is known about the...

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