title: Effects of Epigallocatechin gallate against Enterococcus faecalis biofilm and virulence.
abstract: OBJECTIVE
  Epigallocatechin-3-gallate (EGCG), the most abundant polyphenol in green tea (Camellia sinesis) has been shown to exert antimicrobial effects on numerous bacterial pathogens. However its efficacy against Enterococcus faecalis biofilm, which is associated with persistent root canal infection is unknown. The aims of this study were to investigate the effects of EGCG against E. faecalis biofilm and virulence.
  
  
  METHODS
  Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of EGCG on E. faecalis were determined. The efficacy of EGCG on E. faecalis biofilms was tested by exposing 7-day old E. faecalis biofilm to EGCG. Flow cytometry analysis of hydroxyphenyl fluorescein (HPF) labelled E. faecalis was used to determine if EGCG induced intracellular hydroxyl radical formation. Co-treatment of EGCG with the iron chelator 2,2-dipyridyl (DIP) was carried out to determine if hydroxyl radical generated through Fenton reaction played a role in EGCG-mediated killing of E. faecalis. Furthermore, the effects of EGCG on the expression of virulence genes in E. faecalis were evaluated by quantitative polymerase chain reaction.
  
  
  RESULTS
  EGCG exhibited a MIC and MBC of 5 μg/mL and 20 μg/mL respectively and effectively eradicated E. faecalis biofilms. EGCG induced the formation of hydroxyl radicals in E. faecalis. The addition of DIP protected E. faecalis against EGCG-mediated antibacterial effects. At sub-MIC, EGCG induced significant down-regulation of E. faecalis virulence genes.
  
  
  CONCLUSIONS
  EGCG is an effective antimicrobial agent against both the planktonic and biofilm forms of E. faecalis, inhibiting bacterial growth and suppressing the expression of specific genes related to virulence and biofilm formation. The antimicrobial action of EGCG on E. faecalis occurred through the generation of hydroxyl radical.
authors.affiliation: Faculty of Dentistry, National University of Singapore, Singapore.
authors.forename: Pei
authors.initials: P
authors.lastname: Lee
authors.affiliation: Faculty of Dentistry, National University of Singapore, Singapore. Electronic address: denkst@nus.edu.sg.
authors.forename: Kai Soo
authors.initials: KS
authors.lastname: Tan
mesh_terms: D015082:2,2'-Dipyridyl / Q000494:pharmacology; D000975:Antioxidants / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects*; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology; D013293:Enterococcus faecalis / Q000187:drug effects* / Q000472:pathogenicity*; D005434:Flow Cytometry; D008826:Microbial Sensitivity Tests; D016133:Polymerase Chain Reaction; D014774:Virulence
chemical_list: D000975:Antioxidants; D015082:2,2'-Dipyridyl; D002392:Catechin; C045651:epigallocatechin gallate
keywords: Biofilm; Enterococcus faecalis; Epigallocatechin gallate; Hydroxyl radical; Virulence