Several Cranberry Extracts Act to Prevent Infection by Reducing Bacterial Adhesion

Proanthocyanidins (PACs) comprise of one of the major classes of phytochemicals found in cranberry, which have been extensively studied and found effective in combating adhesion of pathogenic bacteria. The ability of other cranberry constituents to prevent bacterial adhesion remains to be determined.

Investigators at Worcester Polytechnic Institute (MA, USA) and the University of Massachusetts, Dartmouth (USA) used advanced atomic force microscopy techniques to evaluate the effect of various cranberry extracts on bacterial adhesion.

For this purpose the investigators used two strains of Escherichia coli: the pathogenic clinical bacterial strain E. coli B78 and the non-pathogenic control E. coli HB101. The preparations tested included crude cranberry juice extract (CCE); three fractions containing flavonoid classes including proanthocyanidins, anthocyanins and flavonols; selected sub-fractions, and the commercially available flavonol glycoside, quercetin-3-O-galactoside.

Results published in the May 13, 2016, online edition of the journal Food & Function revealed that adhesion forces of the non-pathogenic HB101 lab strain were small and did not change with cranberry treatments, whereas the adhesion forces of the pathogenic E. coli strain B78 showed a significant decrease when treated with cranberry juice extract or fractions. In particular, the fractions that contained flavonols in addition to PACs were more efficient at lowering the force of adhesion.

The sub-fractions containing flavonol glycosides (from juice, fruit, and commercial quercetin) all resulted in reduced adhesion of the pathogenic bacteria to the model probe. This strongly suggested that there was an anti-adhesive role for other classes of cranberry compounds in conjunction with already known PACs, and this finding may have implications for development of alternative anti-bacterial treatments.

"With the emergence of new superbugs that are resistant to current antibiotics, our hope is to better understand the mechanisms of bacterial infection so we can identify potential new antibiotic drug targets," said senior author Dr. Terri Camesano, professor of chemical engineering at Worcester Polytechnic Institute. ""This is an excellent collaboration that pairs what we do on the biophysical side at Worcester Polytechnic Institute with the work that University of Massachusetts, Dartmouth does on the biochemical side."

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Worcester Polytechnic Institute
University of Massachusetts, Dartmouth