UA
researchers are finding a new way to reduce food-borne illness in humans
Oct
28, 2008 10:08 AM, By Source of Article: http://westernfarmpress.com/news/foodborne-illness-1028/ Most people are familiar with Salmonella and its potential to make people
ill. But fewer know about Campylobacter jejuni
– even though it makes more people sick. Raw chicken is one of the most
common carriers of the bacteria, often encountered when cooked meat is placed
on unwashed cutting boards previously used for trimming raw chicken, or when
chicken is not cooked to 165 degrees Fahrenheit. "Campylobacter is now the
No. 1 food-borne pathogen in the A new poultry vaccine in
development at UA offers a unique approach in controlling Campylobacter jejuni infection in chickens before it reaches the
dinner table. In research trials the vaccine has significantly reduced the
pathogen's ability to colonize young chickens' intestines, where the
infection begins. The goal is to halt the contamination before it spreads and
survives on raw chicken sold in stores. "Yet chickens don't
actually cause the disease (nor does it make them ill). It's the organism
they carry that makes people sick," Joens
said. "Right now you can go to any grocery store, get a raw chicken,
test it in a laboratory and find Campylobacter jejuni.
Twenty percent to 80 percent of all broiler houses become contaminated with
Campylobacter." The most common symptoms of
human Campylobacter poisoning, which mimic those of Salmonella and other
gastrointestinal pathogens, include fever, cramps, watery diarrhea and
sometimes dysentery. More severe infections can lead to peritonitis,
autoimmune disease or death. Funded by the U.S. Department of
Agriculture, Joens and UA graduate students started
analyzing Campylobacter's infection process about four years ago, looking for
a way to interrupt it. The laboratory team, which included James Theoret, graduate research associate, and Bibiana Law, assistant research professor, eventually
discovered that the pathogen first attached itself to the surface of the
chick's intestines and then began to multiply. Attacking the
"sticking" mechanism seemed to be the key. When UA researchers sequenced
the intestinal surface protein they identified the gene responsible for
producing Campylobacter’s adherence protein. Then they built a trial vaccine
around it using Salmonella bacteria as a vector, with the assistance of Roy
Curtiss, professor and director of the Center for Infectious Diseases and Vaccinology at Curtiss’ group inserted the
adherence gene into Salmonella bacteria, which is nonpathogenic for poultry.
The resulting live vaccine – containing Salmonella programmed to make the
Campylobacter adhering protein – was fed to young chickens to protect them. “Once the Salmonella in the
vaccine produced the Campylobacter protein, the chicks made antibodies
against it in their intestines,” Joens says.
"In our first study of 15 birds we got a very significant reduction – 98
percent – in Campylobacter infection, compared with a control group. We're
now repeating the trial on a larger scale." The vaccination process is
simple, easy to produce and protective to the chick, according to Joens. The Salmonella lives four to five days, enough
time to stimulate antibody production, and dies. Chickens need to be
vaccinated early because they become infected at just two to three weeks of
age. Joens'
preliminary figures show that 270 million Campylobacter organisms were present
in non-vaccinated birds, compared with 67,000 organisms in the vaccinated
birds. "You need at least 500
organisms to produce disease in humans," he explained. "The
chlorine in the packinghouse chillers usually reduces numbers of bacteria by
1,000 to 100,000 organisms, so the chickens should be free of Campylobacter
after processing." The UA group was the first to
discover the adherence protein, which is only produced when Campylobacter jejuni colonizes certain surfaces, like chicken
intestine and skin. They have a patent pending in both the "If everything goes right
we could have a commercial vaccine in three to five years," Joens said. The vaccine's effect could be
significant: About 8.9 billion broilers go to market annually in the "The vaccine would be a
great intervention method for Campylobacter when the USDA and FDA (Food and
Drug Administration) mandate reduced numbers of food-borne pathogens in
chicken – probably in two to three years," Joens
said. "Once it becomes available, the vaccine should cost about a penny
per chick. More importantly, it should greatly reduce the number of cases of
human Campylobacter gastroenteritis." |
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