Effects of Epigallocatechin Gallate on Viability and Cellular Proteins of Staphylococcus aureus

This study investigated the effect of epigallocatechin gallate (EGCg) on Staphylococcus aureus to determine its mechanism of antibacterial action. Adsorption of EGCg on the cell envelope of S. aureus after EGCg treatment was demonstrated using a FITC-labeled antibody specific to EGCg. After EGCg treatment of S. aureus for 4 h, abnormalities in septum formation and cell segregation were observed at concentrations greater than 250 mg/L, and debris presumed to arise from cell destruction or leakage of cytoplasmic materials was observed around the cells at 500 mg/L. Two-dimensional electrophoresis of proteins prepared from EGCg-treated S. aureus cells revealed the presence of 18 protein spots that disappeared or showed markedly decreased intensity compared to those from control cells. These proteins included DnaK, elongation factor G, DNA-directed RNA polymerase, L-lactate dehydrogenase, pyruvate dehydrogenase, and acetate kinase. Furthermore, S. aureus showed decreased glucose uptake after EGCg treatment. These results suggest that EGCg inhibits the functions of cell-envelope proteins, and it causes cellular damage and disruption of the cells in S. aureus.