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- That underdone chicken sandwich that made you sick long
ago might also give you trouble long after you've forgotten you ever ate
it. Researchers are finding that there might a reason to think food poisoning
could be linked to cancer.
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- Yale University scientists have found that certain bacteria,
including the most common cause of food poisoning, kill intestinal cells
by scrambling their genetic instructions during replication. While no evidence
exists yet to support the claim, the researchers speculate that this deadly
mechanism might pose a cancer risk for organisms, including people, infected
by germs that use it.
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- The notion isn't unheard of: Chronic infection with Helicobacter
pylori, a leading cause of ulcers in humans, is believed to increase the
risk of at least one form of gastric tumor.
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- The study, which appears in this week's issue of the
journal Science, focused on Campylobacter jejuni, the most common form
of bacterial food poisoning in the United States.
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- Campylobacter causes 10,000 reported cases of food poisoning
a year in the United States, but is believed to be linked to as many as
2 million sickenings, health officials say.
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- The germ, which is picked up through contact with raw
or undercooked poultry, leads to severe diarrhea, and while it's generally
not fatal, the Centers for Disease Control and Prevention still says that
up to 500 people a year die from campylobacter infections.
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- Campylobacter belongs to a group of bugs that produce
a poison called CDT. Other members of this clan include strains of Escherichia
coli and shigella, both causes of other food-borne illness. Scientists
have long known about CDT and its ability to destroy gastrointestinal cells,
particularly epithelial, or lining, tissue. But they haven't understood
precisely how the toxin works.
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- Led by Jorge Galan, a specialist in harmful microbes,
the researchers isolated three sub-units of CDT -- "a", "b",
and "c" -- and put them into dishes of human gastric tissue.
Neither a nor c seemed to affect the cells, but the b sub-unit wreaked
havoc, essentially melting down the cell nuclei.
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- In other words, says Galan, CDT "causes DNA damage
and genome instability" that prevent the epithelial cells from replicating.
Although CDT can intoxicate cells at any stage of their life cycle, its
deadly effects come during a particularly vulnerable point during cell
division.
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- Understanding how CDT works, and its effects on DNA,
"should be something that makes us think about the possibility"
that food poisoning might promote tumors, Galan says. Cancers occur when
cells lose their reproductive brakes and begin to divide unchecked.
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- David Schauer, a bacteria expert at the Massachusetts
Institute of Technology, says the link between campylobacter toxin and
cancer is "not off the wall. But it's speculation" until proven
otherwise, he adds.
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- Scientists will have trouble connecting the germ with
tumors, however, since campylobacter and most other gut-loving pathogens
tend to have short tenures in the intestines before they're flushed out,
Schauer says. On the other hand, he notes, "There is some evidence
from animal models that even self-limiting diarrheal disease, if it occurs
at time of exposure to carcinogens, might increase the risk of cancer later
in life."
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- However, Jenifer Coburn, a Tufts University microbiologist
and co-author of a commentary on the journal article, says CDT might be
too effective a killer to be a cancer threat. In lab studies, the toxin
"ultimately does cause cell death. The nuclei aren't dividing, cells
swell up and blow up" rather than multiply out of control. Even so,
she says, what happens in a living person isn't well understood.
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- What To Do
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- To avoid infection by campylobacter and other food-borne
germs, take care handling and preparing your meals. Cook meats thoroughly,
and clean all surfaces and utensils -- including your hands -- well.
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