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Scientists Look to Vaccines in the War on E. Coli --NYTimes [View All]

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Demeter Donating Member (1000+ posts) Send PM | Profile | Ignore Tue May-01-07 10:33 AM
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Scientists Look to Vaccines in the War on E. Coli --NYTimes
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May 1, 2007
Scientists Look to Vaccines in the War on E. Coli

Shousun C. Szu, a scientist at the National Institutes of Health, says the best way to prevent people from being poisoned by deadly E. coli would be to vaccinate all infants against the bacteria... so their immune systems could dispense with the bacteria before they had a chance to multiply and release their toxin in the bloodstream. She and colleagues have developed a vaccine made of the complex sugar that is on the surface of the bacteria, the very O-type polysaccharide that gives O157 its name. The sugar is linked to a protein taken from another bacterium to make it more potent in stimulating the immune system. Dr. Szu and collaborators have tested the vaccine on adult volunteers and on children 2 to 5. The volunteers were not exposed to O157 that would be unethical but they developed antibodies to it. Moreover, when the bacteria were exposed in the laboratory to blood samples from vaccinated people, the microbes were killed. Dr. Szu said the next test would be in infants.

The vaccine is years from the market. As with drugs, testing effectiveness would be difficult, and some experts say it may not make sense to vaccinate every child to protect a small number.
A lot of the economics of it would not be very favorable, said James B. Kaper, an expert on O157 at the Center for Vaccine Development at the University of Maryland. Dr. Szu disagreed, saying, All human lives are precious, especially if you talk to parents who lost their children.

Graeme McRae, a Canadian biotechnology executive, says it would be more practical to inoculate cows instead... a vaccine for cattle developed by Mr. McRaes company, Bioniche Life Sciences, was approved in December for distribution to veterinarians in Canada. Studies have shown that the vaccine can reduce but not eliminate the E. coli shed into manure. Not only does that make the cows cleaner as they go into the slaughterhouse, but it could also conceivably reduce the risk that the germ will spread from a feedlot to a nearby produce field though water or wild animals. Tests at the University of Nebraska found that the vaccine reduced by 70 percent the number of cows shedding O157 into their manure, said Rodney A. Moxley, a professor of veterinary science there. Cows and their manure are considered the major sources of the pathogen. One big potential barrier is that ranchers and feedlots may have little incentive to pay for such treatments, because they do not make the cows grow faster. Nor do they keep the cows healthy, because O157 does not sicken the cows that harbor it. Mr. McRae, president of Bioniche in Belleville, Ontario, said the company would begin to distribute the vaccine in Canada in June or July after it increases manufacturing capacity. The approval there is conditional, and the company has to provide more data showing that the vaccine works. Mr. McRae said he hoped to obtain approval to sell the vaccine in the United States from the Agriculture Department this year. He said feedlots would be charged no more than $2.20 a dose, with two doses needed.

The cattle industry is within pennies of making a profit or not, said Carolyn Hovde Bohach, a professor of microbiology at the University of Idaho who is working on a different E. coli vaccine for cattle. Would it be their responsibility to protect vegetables?

Right now, scientists can do little medically to fight the pathogen, which was responsible for two severe outbreaks last fall, one from contaminated bagged spinach and a second from tainted lettuce served in chain taco restaurants. The main approach has been to try to prevent contamination through careful handling, rigorous inspections and government regulation. Slaughterhouses have already sharply reduced contamination through practices like washing carcasses with hot water, steam or acids. Now the focus is on new procedures and regulations for the fresh-produce industry.


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