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The mechanism of action of a citrus oil blend against Enterococcus faecium and Enterococcus faecalis
Author(s) -
Fisher K,
Phillips C
Publication year - 2009
Publication title -
journal of applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.889
H-Index - 156
eISSN - 1365-2672
pISSN - 1364-5072
DOI - 10.1111/j.1365-2672.2008.04102.x
Subject(s) - enterococcus faecalis , intracellular , enterococcus faecium , extracellular , membrane permeability , antimicrobial , microbiology and biotechnology , chemistry , essential oil , bacteria , biochemistry , biology , biophysics , membrane , food science , escherichia coli , gene , antibiotics , genetics
Aims: The aim was to explore the mechanisms by which a blend of orange ( Citrus sinensis ) : bergamot ( Citrus bergamia ) (1 : 1 v/v) EO (essential oil) (2% v/v) and its vapour (15 mg l −1 air) brings about its antimicrobial effect against Enterococcus faecium and Enterococcus faecalis . Methods and Results: Cells were exposed to the blend in oil or vapour form in a sealed unit. Membrane permeability was measured using an NPN assay and intra and extracellular ATP concentrations were assessed using luminescence. Assays using 3,3‐dipropylthiacarbocyanine and carboxyfluorescein diacetate succinimidyl ester measured membrane potential and intracellular pH changes. TEM images of treated cells indicate morphological differences and show the possible uptake of the EO into the cell. After cells were exposed to EO or vapour, cell permeability increased by ×2 and ×40 respectively. A decrease of 1·5 in intracellular pH, 20 a.u. in membrane potential and 18 pmol mg −1 protein of intracellular ATP occurred. Conclusions: The EO blend affects the cell membrane and cell homeostasis resulting in inhibition of growth or cell death. Significance and Impact of the Study: Understanding the mechanisms by which EOs bring about their antibacterial effect could lead to an alternative to chemical‐based bactericides for use against Enterococcus sp.