Phage therapy could remove foodborne disease from livestock

A bacteria-killing virus found in the feces of some sheep could help remove the dangerous foodborne bacteria Escherichia coli O157:H7 from livestock. Researchers from Evergreen State College in Olympia, Washington present their research today at the 103rd General Meeting of the American Society for Microbiology.

“Here we report a promising new natural way of reducing pathogen concentrations in livestock. This takes advantage of bacteriophages – bacteria-killing viruses, harmless to humans and other animals, which have been used extensively as antibiotics in Eastern Europe and the former Soviet Union for over 50 years,” says Michael Dyen, one of the study researchers.

Dyen and his colleagues report on a new bacteriophage (CEV1) that they isolated from the feces of sheep naturally resistant to gut colonization by E. coli O157:H7. Preliminary trials of CEV1 in the lab have shown that it can be produced easily and can efficiently infect and kill the bacteria under proper conditions. In model systems reflecting the cow/sheep gut, CEV1 completely eliminated the bacteria in 11 days.

“CEV1 and other carefully-selected phages against E. coli O157:H7 could be used to develop an effective management strategy to eradicate this pathogen from livestock,” says Dyen.

Outbreaks of Escherichia coli O157:H7 have been linked to the consumption of hamburger meat, alfalfa sprouts, unpasteurized fruit juice, and even drinking water; more than 75% of the cases can be directly traced to contamination from carrier ruminants. The most recent data suggest that about 28% of the cattle presented for slaughter in the US harbour O157:H7, and similar numbers have been reported in Canada and Europe. The livestock show no signs of illness and the levels are generally low, making contaminated animals hard to identify. Current prevention methodologies have centered on reducing meat contamination in the slaughterhouse and testing all products for human consumption as they leave.

“At present, there are few therapeutic treatments for victims of this potentially deadly infectious agent except supportive therapy to manage the complications of cellular damage,” says Dyen. “Our work focuses on removing O157:H7 from the food chain.”

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This release is a summary of a presentation from the 103rd General Meeting of the American Society for Microbiology, May 18-22, 2003, in Washington, DC. Additional information on these and other presentations at the 103rd ASM General Meeting can be found online at http://www.asm.org/Media/index.asp?bid=17053 or by contacting Jim Sliwa (jsliwa@asmusa.org) in the ASM Office of Communications. The phone number for the General Meeting Press Room is (202) 249-4064 and will be active from 12:00 noon EDT, May 18 until 12:00 noon EDT, May 22.