Understanding why C. difficile causes disease -- it's Hungry
- From: rpautrey2 <rpautrey2@xxxxxxxxx>
- Date: Wed, 30 Jul 2008 08:41:17 -0700 (PDT)
Understanding why C. difficile causes disease -- it's Hungry
May 24, 2007
Researchers studying the genetics behind why C. difficile causes
disease have come to a simple conclusion -- the bacteria do it because
they are starving. That just might help them find a new treatment for
what can sometimes be a very difficult disease to treat.
"The genes responsible for toxin production only seem to be expressed
during periods of nutrient deprivation. This is consistent with the
view that most disease-causing bacteria express their pathogenicity
when they are hungry," says Abraham Sonenshein, professor at the
Sackler School of Graduate Biomedical Sciences at Tufts University and
at Tufts University School of Medicine, at the 107th General Meeting
of the American Society for Microbiology (ASM) on May 24, 2007.
C. difficile bacteria are everywhere — in soil, air, water, human and
animal feces, and on most surfaces in hospital wards. The bacteria
don't cause problems until they grow in abnormally large numbers in
the intestinal tract. This can happen when the benign bacteria that
normally inhabit the intestinal tract are reduced such as when people
take antibiotics or other antimicrobial drugs. Then, C. difficile can
cause symptoms ranging from diarrhea to life-threatening inflammations
of the colon.
In 2002 a new, more virulent strain began appearing in hospitals in
the United States and Canada. Recently, this strain was shown to be
responsible for more than half of all cases in a representative
sampling in Quebec. The highly virulent strain has a much higher toxin
production which leads to more destructive and deadly disease, says
Vivian Loo of McGill University.
Sonenshein is studying a five-gene region of the bacterium’s
chromosome known as the tcd locus. Two of the genes code for the
toxins the bacterium produces that cause disease and a third gene
codes for a protein that makes a hole in the organism’s cell envelope
to let the toxins out. The last two genes are of greatest interest to
Sonenshein and his colleague, Bruno Dupuy from the Institut Pasteur.
One codes for a protein, known as R, that is necessary for the
expression of the first three genes and the other codes for a protein
called C that prevents R from acting.
A mutation in the C protein gene, leaving R unchecked, is the cause of
the hypervirulent strain. Sonenshein and his colleagues are currently
working to identify a protein that might shut down the gene that codes
for R. By identifying such a protein, Sonenshein hope to find a way to
change the appetite of the bacteria. "If we find a way to shut down
toxin production in the hypervirulent strain, we might have a new way
to treat the disease," says Sonenshein.
Source: American Society for Microbiology
This news is brought to you by PhysOrg.com
http://www.physorg.com/news99220113.html
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