Tannins Found in Cranberries Act as Antibacterial Agents

A Cranberry a Day Keeps Bacteria Away

Researchers are now proving what doctors have known for years. Cranberries contain antibacterial qualities that are effective in treating urinary tract infections, stomach ulcers, and more. Worcester Polytechnic Institute (WPI) researchers have found that tannins in cranberries have the ability to alter E. coli bacteria. These tannins, called proanthocyanidins or PACs, prevent E. coli from adhering to cells in the body thereby preventing infection. These PACs are present in cranberry juice and other cranberry products.

It has long been know that cranberry juice is effective at preventing urinary tract infections (UTIs). The conventional, though unproven, thought was that the cranberry juice caused the E. coli bacteria to lose its stickiness and get washed away in urine. However, the mechanisms which underlie the health benefits of cranberries and its products have been unknown. Now, through the use of atomic force microscopes and other tools it is becoming clear that PACs interact with E. coli on a molecular level.

Terri Camesano, Associate Professor of Chemical Engineering at WPI, headed the cranberry research team which found that cranberry juice causes an energy barrier that keeps bacteria from getting close to the urinary tract lining. This reduction in adhesion is found when at least a five percent solution of cranberry juice cocktail is present. In addition, E.coli grown in cranberry juice are unable to form biofilms. Biofilms are clusters of high concentrations of bacteria and are required for infections to develop, especially with indwelling catheters and other biomedical devices. Cranberry juice also inhibits the ability of E.coli to produce a molecule, IAA, which is used by bacteria as a way to communicate their location to other bacteria. The presence of IAA enables bacteria to sense whether their population is large enough to form a biofilm or initiate an infection.