Mechanism of the combined anti-bacterial effect of green tea extract and NaCl against Staphylococcus aureus and Escherichia coli O157:H7

Motokazu Nakayama, Naofumi Shigemune, Takashi Tsugukuni, Hitomi Jun, Tomoyo Matsushita, Yoko Mekada, Masahiro Kurahachi, Takahisa Miyamoto

Research output: Contribution to journalArticle

31 Citations (Scopus)

Abstract

The mechanism of the combined anti-bacterial effect of green tea extract (GTE) and NaCl against Staphylococcus aureus NBRC 13276 and Escherichia coli O157:H7 was investigated. After treatment for 1 h, GTE was more effective against S. aureus than E. coli O157:H7, and combined GTE/NaCl treatment caused greater cellular damage in S. aureus NBRC 13276, where it was bactericidal, than E. coli O157:H7. Compared to treatment with 1.0 mg/mL GTE, which had no effect on the survival rate of E. coli O157:H7 after 48 h, treatment with 4% NaCl alone caused greater cellular damage. Moreover, bacteria pretreated with NaCl showed delayed growth in the presence of GTE. It is therefore likely that susceptibility of E. coli O157:H7 to GTE was increased by exposure to NaCl. E. coli O157:H7 pretreated with GTE and NaCl did not multiply in the presence of GTE. Visualization of the catechin components of GTE-treated bacteria using an electron microscope and SDS-PAGE analysis of cell proteins showed that GTE attached to proteins on the surface of the bacteria to form high-molecular weight complexes, suggesting the possibility that GTE inhibits the uptake and secretion of substrates and inhibits enzyme activity. Notably, after the GTE treatment for 1 h, both bacterial strains suffered injury but recovered by cultivation in rich medium. The damage and aggregation of proteins caused by GTE treatment were repaired upon treatment with LP diluent.

Original languageEnglish
Pages (from-to)225-232
Number of pages8
JournalFood Control
Volume25
Issue number1
DOIs
Publication statusPublished - May 1 2012
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Biotechnology
  • Food Science

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