Worcester Polytechnic Institute
WORCESTER, Mass., Sept. 10 /PRNewswire/ -- Compounds in cranberry juice have the ability to change E. coli
bacteria, a class of microorganisms responsible for a host of human
illnesses (everything from kidney infections to gastroenteritis
to tooth decay), in ways that render them unable to initiate an
infection. The results of this new research by scientists at Worcester
Polytechnic Institute (WPI) suggest that the cranberry may provide
an alternative to antibiotics, particularly for combating E. coli
bacteria that have become resistant to conventional treatment.
The new findings, which will be presented on Sunday, Sept. 10,
at the annual meeting of the American Chemical Society in San Francisco,
for the first time begin to paint a detailed picture of the biochemical
mechanisms that may underlie a number of beneficial health effects
of cranberry juice that have been reported in other studies over
the years.
Many of those studies have focused on the ability of cranberry
juice to prevent urinary tract infections (UTIs), which each year
affect eight million people -- mostly women, the elderly, and infants
-- resulting in
$1.6 billion in health care costs. Until now, scientists have not
understood exactly how cranberry juice prevents UTIs and other
bacterial infections, though they have suspected that compounds
in the juice somehow
prevent bacteria from adhering to the lining of the urinary tract.
The new findings reveal how the compounds interfere with adhesion
at the molecular level.
The new results will be incorporated in two presentations during
a session that runs from 8:30 to 11:40 a.m. PDT in the Windsor
Room of the Sir Francis Drake Hotel.
The research, by Terri Camesano,
associate professor of chemical engineering at WPI, and graduate
students Yatao Liu and Paola Pinzon-Arango, and funded, in part,
by the National Science Foundation, shows that a group of tannins
(called proanthocyanidins) found primarily in cranberries affect
E. coli in three devastating ways, all of which prevent the bacteria
from adhering to cells in the body, a necessary first step in all
infections:
* They change the shape of the bacteria from rods to spheres.
* They alter their cell membranes.
* They make it difficult for bacteria to make contact with cells,
or from latching on to them should they get close enough. For most
of these effects, the impact on bacteria was stronger the higher
the concentration of either cranberry juice or the tannins, suggesting
that whole cranberry products and juice that has not been highly
diluted may have the greatest health effects.
The new results build on previously published work, in which Camesano
and her team showed that cranberry juice causes tiny tendrils (known
as fimbriae) on the surface of the type of E. coli bacteria responsible
for
the most serious types of UTIs to become compressed. Since the
fimbriae make it possible for the bacteria to bind tightly to the
lining of the urinary tract, the change in shape greatly reduces
the ability of the
bacteria to stay put long enough to initiate an infection.
More recently, Camesano and Liu have shown that chemical changes
caused by cranberry juice also create an energy barrier that keeps
the bacteria from getting close to the urinary tract lining in
the first place.
New work by Camesano and Pinzon-Arango shows that cranberry juice
can transform E. coli bacteria in even more radical ways. The researchers
grew E. coli over extended periods in solutions containing various
concentrations of either cranberry juice or tannins. Over time,
the normally rod-shaped bacteria became spherical -- a transformation
that has never before been observed in E. coli.
Remarkably, the E. coli bacteria, all of which fall into a class
called gram-negative bacteria, began behaving like gram-positive
bacteria -- another never-before-seen phenomenon. Since gram-negative
and gram-positive bacteria differ primarily in the structure of
their cell membranes, the results suggest that the tannins in cranberry
juice can alter the membranes of E. coli.
A final, more preliminary result that will be presented at the
ACS meeting suggests that E. coli bacteria exposed to cranberry
juice appear to lose the ability to secrete indole, a molecule
involved in a form of
bacterial communication called quorum sensing. E. coli use quorum
sensing to determine when there are enough bacteria present at
a certain location to initiate a successful infection.
"We are beginning to get a picture of cranberry juice and, in particular,
the tannins found in cranberries as, potentially potent antibacterial
agents," Camesano says. "These results are surprising and intriguing,
particularly given the increasing concern about the growing resistance
of certain disease-causing bacteria to antibiotics."
About Worcester Polytechnic Institute
Founded in 1865 in Worcester, Mass., WPI was one of the nation's
first engineering and technology universities. WPI's 18 academic
departments offer more than 50 undergraduate and graduate degree
programs in science, engineering, technology, management, the social
sciences, and the humanities and arts, leading to the BA, BS, MS,
ME, MBA and PhD. WPI's world-class faculty work with students in
a number of cutting-edge research areas, leading to breakthroughs
and innovations in such fields as biotechnology, fuel cells, nanotechnology,
and information security. Students also have the opportunity to
make a difference to communities and organizations around the world
through the university's innovative Global Perspective Program.
There are more than 20 WPI project centers throughout North America
and Central America, Africa, Australia, Asia, and Europe.
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