Antibacterial characteristics and activity of Vaccinium macrocarpon proanthocyanidins against diarrheagenic Escherichia coli

This research investigated the antibacterial properties of American cranberry (Vaccinium macrocarpon) proanthocyanidins against enteropathogenic and enterotoxigenic Escherichia coli by determining the minimum inhibitory concentrations (MIC) and minimum bactericidal (MBC) concentrations and the effect of pH of proanthocyanidins as well as examining the integrity of cell membrane of treated bacteria. The results of MIC and MBC of proanthocyanidins for antibacterial investigation were 18 and 36 mg/ml, respectively. The MBC of proanthocyanidins showed an inhibitory effect with a 6-log CFU/ml reduction of all E. coli strains tested. Proanthocyanidins demonstrated better inhibitory action than organic acids with a 6-log CFU/ml reduction at the same pH (4). The cell membrane permeability of the tested E. coli revealed significant increase in the uptake of PI after treating with different concentrations of proanthocyanidins. The damage of cell membranes was observed using transmission electron microscopy. Accordingly, cranberry proanthocyanidins may be used as natural diarrhea preventative.