Cranberry's
in plaats van antibiotica.*
Uit eerdere onderzoeken is al gebleken dat cranberry's goed zijn bij en tegen infecties van de urinewegen en andere bacteriële infecties. Uit een nieuwe studie nu blijkt hoe de bacteriën door cranberry's worden aangepakt. Het zijn de bioactieve tanninen (proanthocyanen) in de cranberry's die de bacterie, in het bijzonder de E.coli, aanpakken. Zij veranderen de vorm van de bacterie, van staafjes in rondjes. Verder veranderen ze de celmembranen van de bacterie en verhinderen ze dat bacteriën zich aan andere cellen vasthechten. De meeste tanninen worden gevonden in de cranberry's zelf of in zeer geconcentreerd sap.
Compounds
In Cranberry Juice Show Promise As Alternatives To Antibiotics For Treating.
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 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 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.
(Sept.
2006)