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A shrimp cocktail is
a culinary delight, but scientists warn that cooked and ready-to-eat
shrimp bought at supermarkets may still harbor dangerous food pathogens.
Douglas Marshall, a professor
of food science at Mississippi State University was surprised that
he could isolate so many pathogens on a popular ready-to-eat product.
The pathogens should have been killed when the shrimp were processed
as ready-to-eat food, he said.
Marshall speculated that
the problem could be caused by inadequate cooking of shrimp at plants,
poor sanitation, contamination by workers or poor water quality
in Third World countries where some of the products were processed.
Some of the pathogens
he found, he explained, are not normally found in seafood, but are
commonly found carried by humans or animals.
The Institute of Food
Technologists earlier this year warned that supermarket trends towards
ready-to-eat products could lead to outbreaks of food-borne diseases.
Some scientists recommend that, as a precaution, prepared foods
be re-cooked to kill any pathogens that might have developed.
Marshall and graduate
student Gianna Duran launched their study to see if shrimp might
have antibiotic-resistant bacteria. They purchased 13 packages of
ready-to-eat shrimp from different manufacturers at local grocery
stores. Some were refrigerated products, and others frozen. The
frozen shrimp were then thawed for the study.
The scientists concluded
that 42 percent of the bacteria cultured from the shrimp were drug-resistant.
Marshall said fish and shrimp farms use drugs to treat diseases
in their stock, and that it is not surprising there should be drug-resistant
strains in the shrimp sold at supermarkets.
But the study also found
pathogens that should have been killed in the preparation process,
including a waterborne agent called vibrio vulnificus. Cases of
diarrhea and even death have been linked to raw oysters and clams
tainted with the pathogen.
Other pathogens, like
E. coli, staphylococcus and shigella, were also found in the shrimp,
although they are carried in the intestines of warm-blooded animals.
The study said that this suggests fecal contamination of shrimp,
probably after cooking by workers using unsanitary practices.
Marshall suggested that
people with compromised immune systems should re-heat prepared foods
before consuming them.
Annual
Meeting of the American Society for Microbiology in Salt Lake
City May 2002
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