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Targeting E. Coli Bacteria at Their Source

By Luis Pons
August 4, 2004

Agricultural Research Service scientists and colleagues are looking inside the cow in order to spot--and to stop-- bacteria that cause a particularly nasty E. coli-related disease.

Microbiologist Evelyn Dean-Nystrom and veterinary medical officer William Stoffregen of the ARS National Animal Disease Center (NADC) in Ames, Iowa, are pinpointing where microbes called enterohemorrhagic Escherichia coli O157:H7 lurk in calves.

Also, Nystrom is helping researchers at the Uniformed Services University of the Health Sciences in Bethesda, Md., develop and test an oral vaccine that eliminates these bacteria from cattle.

E. coli O157:H7 is the most common infectious cause of bloody diarrhea in people in the United States. Hemolytic uremic syndrome, a potential consequence of its infection, is the primary cause of acute kidney failure in U.S. children.

Undercooked or raw ground beef has been implicated in many E. coli O157:H7 outbreaks in humans. However, the causative bacteria have almost no discernable effect in cattle, making them hard to detect there.

Nystrom and Stoffregen found that, in addition to intestines, calves' gall bladders may be a good place to check whether an E. coli O157:H7 infection has taken place. This finding indicates that including gall bladders in samples cultured for E. coli O157:H7 may help identify infected cattle at slaughter.

The oral vaccine, developed at the Bethesda university by graduate student Nicole A. Judge, uses intimin, a protein on the outer membrane of the O157:H7 strain that the E. coli bacteria need for attaching themselves to intestinal tissue. Nystrom assisted with development of the vaccine--supervised by microbiologist and department chair Alison O'Brien--early on, by showing that calves injected with purified bacterial intimin would develop antibodies against it.

Nystrom works in NADC's Preharvest Food Safety and Enteric Diseases Research Unit, while Stoffregen works in the center's Bacterial Diseases of Livestock Research Unit.

Read more about the research in the August issue of Agricultural Research magazine.

ARS is the U.S. Department of Agriculture's chief scientific research agency.