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 per cent 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.