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http://www.grist.org/industrial-agriculture/2011-05-31-you-want-superbugs-with-that1
by Barry Estabrook
2 Jun 2011
Stuart Levy once kept a flock of chickens on a farm in the rolling countryside west of Boston. No ordinary farmer, Levy is a professor of molecular biology and microbiology and of medicine at Tufts University School of Medicine. This was decades ago, and his chickens were taking part in a never-before-conducted study. Half the birds received feed laced with a low dose of antibiotics, which U.S. farmers routinely administer to healthy livestock -- not to cure illness, but merely to increase the animals' rates of growth. The other half of Levy's flock received drug-free food.
Results started showing up almost instantly. Within two days, the treated animals began excreting feces containing E. coli bacteria that were resistant to tetracycline, the antibiotic in their feed. (E. Coli, most of which are harmless, normally live in the guts of chickens and other warm-blooded animals, including humans.) After three months, the chickens were also excreting bacteria resistant to such potent antibiotics as ampicillin, streptomycin, carbenacillin, and sulfonamides. Even though Levy had added only tetracycline to the feed, his chickens had somehow developed what scientists now call "multi-drug resistance" to a host of antibiotics that play important roles in treating infections in people. More frightening, although none of the members of the farm family tending the flock were taking antibiotics, they, too, soon began excreting drug-resistant strains of E. coli.
When Levy's study was published in The New England Journal of Medicine in 1976, it was met with skepticism. "The other side -- industry -- could not believe that this would have happened. The mood at the time was that what happens in animals does not happen in people," said Levy, who serves as president of the Alliance for the Prudent Use of Antibiotics, in a telephone interview from his office at Tufts. "But we had the data. It was obvious to us even then that using antibiotics this way was an error and should be stopped."
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