Red Meat Helps Spur a
Food Poison Germ
Wednesday, October 29, 2008; 12:00 AM
WEDNESDAY, Oct. 29 (HealthDay News) -- Researchers say they have found a bacterium that causes food poisoning by targeting a non-human molecule that's absorbed into the body through red meat.
Subtilase cytotoxin, a potent bacterial toxin produced by certain kinds of E. coli bacteria, zeroes in on human cells with a non-human, cellular molecule on their surface. One of its favorite targets appears to be N-glycolylneuraminic acid (Neu5Gc), a type of glycan, or sugar molecule, found in high levels in red meat and dairy products.
Subtilase cytotoxin causes bloody diarrhea and can lead to a potentially fatal disease called haemolytic uraemic syndrome (HUS), which can be contracted by consuming contaminated red meat.
The findings were to be published online Oct. 29 in the journalNature.
Since humans lack the gene responsible for production of Neu5Gc, it was previously thought that they should be resistant to the toxin. However, the researchers discovered that places where Neu5Gc becomes incorporated into the human body coincide with toxin binding.
"Ironically, humans may set themselves up for an increased risk of illness from this kind of E. coli bacteria present in contaminated red meat or dairy, because these very same products have high-levels of Neu5Gc," research team member Dr. Ajit Varki, a professor of the University of California, San Diego School of Medicine, said in a news release issued by his university. "The Neu5Gc molecule is absorbed into the body, making it a target for the toxin produced by E. coli."
The researchers said that people should eat only well-cook meat or pasteurized dairy products, because both processes destroy contaminating bacteria.
More information
The U.S. National Institute of Diabetes and Digestive and Kidney Diseases has more about bacterial or food-borne illness.
SOURCE:
washingtonpost.com
Eating Red Meat Sets
Up Target For Disease Causing Bacteria
Main Category: Infectious Diseases / Bacteria / Viruses
Also Included In: Nutrition / Diet
Article Date: 30 Oct 2008 - 0:00 PDT
Source:
Offering another reason why eating red meat could be bad for
you, an international research team, including University of California, San
Diego School of Medicine professor Ajit Varki, M.D., has uncovered the first example of a bacterium
that causes food poisoning in humans when it targets a non-human molecule
absorbed into the body through red meats such as lamb, pork and beef.
In findings to be published on line October 29th in advance
of print in the journal Nature, the scientists discovered that a potent
bacterial toxin called subtilase cytotoxin
specifically targets human cells that have a non-human, cellular molecule on
their surface. The molecule N-glycolylneuraminic acid
(Neu5Gc) is a type of glycan, or sugar molecule, that
humans don't naturally produce.
Subtilase cytotoxin
is produced by certain kinds of E. coli bacteria, causing bloody diarrhea and a
potentially fatal disease called haemolytic uraemic syndrome (HUS) in humans. Humans usually become
infected after eating contaminated red meat, which is why this is also known as
"hamburger" disease.
Varki, UC San Diego School of
Medicine distinguished professor of medicine and cellular and molecular
medicine, and co-director of the UCSD Glycobiology
Research and Training Center, previously discovered that humans don't produce
Neu5Gc because they lack the gene responsible for its production. Therefore, it
was thought that humans should be resistant to the toxin.
"Ironically, humans may set themselves up for an
increased risk of illness from this kind of E. coli bacteria present in contaminated
red meat or dairy, because these very same products have high-levels of
Neu5Gc," Varki explained. "The Neu5Gc
molecule is absorbed into the body, making it a target for the toxin produced
by E. coli."
In the Nature study, the researchers discovered that sites
where the Neu5Gc has been incorporated into the human body coincide with toxin
binding. "When the toxin binds to the non-human Neu5Gc receptors, it can
result in serious food-poisoning and other symptoms in humans," said Varki. The research emphasizes the need for people to eat
only well-cook meat or pasteurized dairy products, processes that destroy
contaminating bacteria.
Five years ago, Varki and his
colleagues at the UC San Diego School of Medicine published a paper in the
Proceedings of the National Academy of Sciences describing how Neu5Gc is
absorbed into human tissues including the surface of cells lining the
intestines and blood vessels as a result of eating red meat and milk products.
At the time, the researchers also showed that this foreign molecule generates
an immune response that could potentially lead to inflammation in human
tissues. The UC San Diego study was the first to investigate human dietary
absorption of the Neu5Gc glycans which, while not
produced in humans, does occur naturally in red meats. Levels are very low or
undetectable in fruits, vegetables, eggs, poultry and fish. The researchers
proved that people who ingest Neu5Gc incorporate some of it into their tissues,
and demonstrated that many generated an immune response against the molecule,
conjecturing that a lifetime of gradual incorporation of this glycan "invader" could result in disease.
The UC San Diego team included postdoctoral fellow Jonas C. Löfling and professor of pathology Nissi
M. Varki. The international research collaborators
included Jamie Rossjohn and Dr. Travis Beddoe, as well as Emma Byres and Matthew C.C. Wilce from Monash University in
Victoria, Australia; Adrienne W. Paton, James C. Paton, Ursula M. Talbot and
Damien C. Chong of the University of Adelaide, South Australia; David F. Smith,
Emory University School of Medicine, Atlanta, Georgia; and Hai
Yu, Shengshu Huang and Xi Chen, UC Davis Department
of Chemistry.
The research was funded by the National Institutes of
Health, and by
CA 92103
http://www.sandiego.edu
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