The polyphenol (-)-epicatechin gallate disrupts the secretion of virulence-related proteins by Staphylococcus aureus

Aim: (-)-Epicatechin gallate (ECg) modifies the morphology, cell wall architecture and beta-lactam antibiotic susceptibility of Staphylococcus aureus. As these effects result primarily from intercalation into the bacterial cytoplasmic membrane, the capacity of ECg to modulate the secretion of two key staphylococcal virulence factors, coagulase and alpha-toxin, was examined. Methods and Results: Bioassays were used to determine coagulase and haemolysin activity in culture supernatants of a number of S. aureus isolates grown in the presence and absence of ECg; alpha-toxin secretion was also evaluated by immunoblotting. Growth in ECg reduced the levels of activity of both proteins in culture supernatants; the effects could only be partly explained by ECg-mediated inhibition of bioactivity and by induction of secreted proteases. Conclusion: ECg suppresses the secretion of coagulase and alpha-toxin by clinical isolates of S. aureus. Significance and Impact of the Study: The observation that secretion of key components of staphylococcal virulence can be compromised by a naturally occurring polyphenol supports the notion that ECg and related compounds may have therapeutic utility for the control of infections that are currently difficult to treat due to the propensity of methicillin-resistant S. aureus to accumulate antibiotic resistance genes.