of humanity’s worst nightmares. But thanks to advances in genetic
research, scientists are finally beginning to understand why.
Americans first became acquainted with this deadly pathogen in 1993,
when several people, mostly children, died from exposure to the
pathogen after consuming undercooked ground beef at a chain
restaurant in the Pacific Northwest. Hundreds of others survived the
ordeal after enduring days of excruciatingly severe nausea, cramping
and bloody diarrhea.
Since then, the pathogen, known by the unwieldy name
E.coli O157:H7, has triggered hundreds of illnesses throughout the
world, ranging from bloody diarrhea to kidney failure.
While food scientists have been aware of the deadly
pathogen since the early 1980’s, they have not understood what
genetic properties distinguished it from other, more common strains
of E.coli. Even more important, they couldn’t understand what made
it so deadly.
Now they do.
"The greatest problem associated with O157:H7
was that it simply was an unknown organism," Weese says.
"Although E.coli is an ancient organism, this particular one
was only discovered less than a couple of decades ago," says
Dr. Jean Weese, a food scientist with the Alabama Cooperative
"We’ve known for a long time that E.coli
O157:H7 acquired some genetic traits from other toxins. But we
simply weren’t aware of how extensive this was until
recently," she says.
After comparing more than 5,000 genes of this
dreaded pathogen with other, less harmful E.coli strains, scientists
uncovered what has been described as a "host of unexpected
Indeed, compared with other E.Coli strains,
scientists have determined O157:H7 possesses more than 1,000
additional genes, some of which appear to contribute directly to the
horrific human suffering that often accompanies exposure to the
Scientists already had identified two E.coli toxins
that appeared to cause fatal kidney damage. But based on preliminary
testing, they believe several more genes also are likely
Antibiotics are effective in killing the pathogens.
However, even while succumbing to the antibiotics, the bacteria, in
their death throes, release harmful toxins, wreaking havoc
throughout the body.
Now that scientists have uncovered the genetic
makeup of these bacteria, they will be better prepared to deal with
E.coli outbreaks in the future.
"We’ve been constantly working to develop new
antiseptics, but now that we know how this pathogen functions, we’ll
be better equipped to focus on chemicals that can be targeted to
specific genes, either changing them into nonpathogenic agents or
killing them outright," Weese says.
In fact, research already is under way at Auburn
University to identify chemicals that can eliminate the pathogens in
food, she says.
Jean Weese, Extension food scientist, Alabama Cooperative
Extension System, 334-844-3269.