Targeting E. Coli Bacteria at Their
Source By Luis
August 4, 2004
Service scientists and colleagues are looking inside the cow in order to
spot--and to stop-- bacteria that cause a particularly nasty E.
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
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
Safety and Enteric Diseases Research Unit, while Stoffregen works in the
center's Bacterial Diseases of Livestock Research Unit.
about the research in the August issue of Agricultural Research
ARS is the U.S. Department of
Agriculture's chief scientific research agency.