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Animal producers know that the current trend is to discourage the continued use of antibiotics in livestock. However, recent Food Safety Consortium-supported research at Iowa State University shows that antibiotics may be helpful in reducing the pathogen Escherichia coli O157:H7 in swine.
Nancy Cornick, the Iowa State associate professor of veterinary microbiology who conducted the study, said a 2001 survey showed that 80% of producers treated their swine with antibiotics, mostly for disease prevention and growth promotion. In her study, Cornick examined the usage of three particular antibiotics — tylosin, chlortetracycline and bacitracin methylene disalicylate — that are generally used at dosages to encourage growth promotion.
Cornick's project showed that the pigs fed the diet supplemented with chlortetracycline and tylosin shed significantly less E. coli O157:H7 than pigs fed antibiotic-free diets.
"The antibiotics I chose were the ones that were most commonly added at subtherapeutic doses, which is what they're usually looking for with growth promotion," Cornick said.
Even without E. coli O157:H7 being a widespread occurrence in pigs, Cornick believes the potential makes it a problem worth investigating. With low level fecal shedding, the pigs can transmit the pathogen among each other. If usage of antibiotics drops off, Cornick wonders if there would be a corresponding increase of E. coli O157:H7.
"Maybe there would be or if I can find another reason why E. coli O157:H7 isn't in swine then maybe that's something cattle producers can use as a management strategy," she said.
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