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Salmonella
and campylobacter are bacteria
pathogenic to humans and are some of the leading causes of food-borne
illness around the world. According to ongoing research of the University
of Arizona (UA) shellfish, such as oysters and clams
are increasingly becoming harbingers of these creatures and pose serious
risk, especially since they are often eaten raw.
Although these bacteria are part of the normal and
healthy flora in some animals such as chickens, they can cause disease
in humans.
Shellfish do not usually harbor these organisms,
but they can acquire them by filtering water through their systems by
which the bacteria concentrates in their meat. Researchers state that
the shellfish are becoming contaminated because they
often reside in estuaries where fecal runoff from sewage can pollute the
water. Because shellfish feed by filtering water to gather
nutrients, they also pick up fecal pathogens that can thrive in their
tissues without killing them.
Researchers are trying to determine the extent of
shellfish contamination with salmonella and campylobacter across the U.S.
and they have begun collecting clams and oysters from several bays and
rivers in Oregon and North Carolina.
So far they have found salmonella
in 50% to 70% percent and campylobacter
in 10%-15% of the clams and oysters tested.
Each state regulates its own oyster farms, but most
states only require the water be tested for E. coli. Testing the water
for salmonella and campylobacter is not feasible since the bacteria concentrate
in the tissues. The only way to test for contamination is to test the
meat.
In order to reduce E. coli levels at the farms,
the water in the tanks are changed often. However, since
salmonella and campylobacter concentrate in the tissues, this method does
nothing to reduce levels.
The researchers want to bring attention to the contaminated
waters by testing oyster meat from different locations for the presence
of the two pathogens, attempting to locate the sources of the pollution,
and then reporting their findings to the FDA so that they can clean up
the contamination sources.
Salmonella and Campylobacter
Both campylobacter and salmonella species can survive
in meat products and in fresh and salt water for days.
In Arizona, where the researchers are based, salmonella
is the number one cause of food-borne illness and campylobacter is third,
although campylobacter food poisonings have been increasing recently.
Researchers note that most people pick both of these
bacteria up by eating poultry placed on contaminated cutting boards and
counter tops.
"People will trim the raw chicken on the cutting
board, transfer it to a plate, take it to the barbecue, cook it, and then
put it back on the same unwashed plate and cutting board the raw
chicken was on," says Lynn A. Joens, a UA veterinary microbiologist
says. "Salmonella in particular is on both the skin of the poultry
and in the meat, and doesn't just wash off. Only cooking to the proper
temperature of 160 degrees gets rid of it."
Dr. Joens says the prevalence of campylobacter and
salmonella food poisoning may be higher than current figures show because
a lot of cases probably go unreported.
University of Arizona
- Ongoing Studies - 12/1/2000
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