The mechanism of action of a citrus oil blend against Enterococcus faecium and Enterococcus faecalis

Kimberly Fisher, Ceri Phillips

Research output: Contribution to journalArticleResearchpeer-review

Abstract

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.
Original languageEnglish
Pages (from-to)1343-1349
Number of pages6
JournalJournal of Applied Microbiology
DOIs
Publication statusPublished - 9 Mar 2009
Externally publishedYes

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Enterococcus faecium
Citrus
Enterococcus faecalis
Oils
Volatile Oils
Membrane Potentials
Permeability
Adenosine Triphosphate
Enterococcus
Luminescence
Homeostasis
Cell Death
Air
Cell Membrane
Membranes
Growth
Proteins

Cite this

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title = "The mechanism of action of a citrus oil blend against Enterococcus faecium and Enterococcus faecalis",
abstract = "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.",
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The mechanism of action of a citrus oil blend against Enterococcus faecium and Enterococcus faecalis. / Fisher, Kimberly; Phillips, Ceri.

In: Journal of Applied Microbiology, 09.03.2009, p. 1343-1349.

Research output: Contribution to journalArticleResearchpeer-review

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