Antipathogenic Properties of Green Tea Polyphenol Epigallocatechin Gallate at Concentrations below the MIC against Enterohemorrhagic Escherichia coli O157:H7

Abstract

The inhibitory effects of green tea polyphenol epigallocatechin gallate (EGCG) on virulence phenotypes and gene expression regulated by quorum sensing (QS) in Escherichia coli O15TH7 were demonstrated at concentrations of 1 to 100 mu g/ml, which are lower than the MIC (539 +/- 22 mu g/ml). At 25 mu g/ml, the growth rate was not affected, but autoinducer 2 concentration, biofilm formation, and swarm motility decreased to 13.2, 11.8, and 50%, respectively. Survival at 5 days of nematodes (Caenorhabditis elegans) that were fed the pathogen without and with EGCG were 47.1 and 76%, respectively. Real-time PCR data indicated decreased transcriptional level in many quorum sensing-regulated virulence genes at 25 mu g/ml. Our results suggest that EGCG at concentrations below its MIC has significant antipathogenic effects against E. coli O157:H7.