Unlike many so-called health foods, the purported ability of cranberries to fight infections — especially urinary tract infections — is actually backed up by science. Now, a team of chemical engineers from McGill University has demonstrated that cranberry-derived compounds could be incorporated into catheters and other implantable materials to fight off bacterial pathogens.
Traditionally, the anti-bacterial activity of cranberries has been ascribed to a class of compounds called proanthocyanidins (PACs). But a team led by McGill chemical engineering professor Nathalie Tufenkji has shown that pure cranberry powder has a higher inhibition effect than can be explained by PACs alone. “We think there are other compounds in the whole fruit that we’re missing out on by just working with PACs,” says Tufenkji. Additional experiments by Tufenkji’s team have shown that PACs and other cranberry-derived compounds work via multiple mechanisms. In some bacteria, they interfere with iron metabolism, while in others they impair the expression of a gene called fliC, which is needed to produce the flagella bacteria use to swim and crawl along surfaces.
In their most recent paper, published in Colloids and Surfaces B: Biointerfaces, the team showed that both PACs and cranberry powder can be incorporated into polymers like silicone, commonly used for implants. Disks of silicone impregnated with cranberry-derived materials resisted colonization by the bugs by interfering with their motility. Of course, the same effect can be obtained with antibiotics, but Tufenkji says cranberry has certain advantages. “There’s the public acceptance aspect; having a natural material versus silver nanoparticles or antibiotics,” says Tufenkji. “As well, we’re not killing the cells, we’re not even hurting the cells. That means they’re less prone to developing resistance.”