Iron sequestration is not the main mechanism in the inhibition of Staphylococcus aureus growth by cranberry phytochemicals

Abstract

Some edible berries such as cranberry have been shown to process antimicrobial activity. One of the antimicrobial actions is hypothesized to be sequestration of iron required for bacterial growth as berry phytochemicals contain strong iron binding groups. Cranberry phytochemicals obtained by solid phase extracts (SPE) from a commercial cranberry juice were studied for their inhibition of Staphylococcus aureus. At 100 µg gallic acid equivalents/mL of phenolic materials, cranberry SPE inhibited bacteria growth by about 0.82-1.1 log units based on the number of colony forming units/mL. However, supplementation of growth media containing cranberry phytochemicals with added iron at levels high enough to overcome media iron deficiency failed to restore bacteria growth. These would indicate that sequestration of iron is not a major antimicrobial mechanism ofcranberry phytochemicals.