11. Antibacterial and Antifungal Activities of Essential Oils

  1. Halldor Thormar
  1. Katherine A. Hammer and
  2. Christine F. Carson

Published Online: 14 DEC 2010

DOI: 10.1002/9780470976623.ch11

Lipids and Essential Oils as Antimicrobial Agents

Lipids and Essential Oils as Antimicrobial Agents

How to Cite

Hammer, K. A. and Carson, C. F. (2011) Antibacterial and Antifungal Activities of Essential Oils, in Lipids and Essential Oils as Antimicrobial Agents (ed H. Thormar), John Wiley & Sons, Ltd, Chichester, UK. doi: 10.1002/9780470976623.ch11

Editor Information

  1. Faculty of Life and Environmental Sciences, University of Iceland, Reykjavik, Iceland

Author Information

  1. Discipline of Microbiology and Immunology (M502), School of Biomedical, Biomolecular and Chemical Sciences, The University of Western Australia, Crawley, Western Australia, Australia

Publication History

  1. Published Online: 14 DEC 2010
  2. Published Print: 25 JAN 2011

ISBN Information

Print ISBN: 9780470741788

Online ISBN: 9780470976623

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Keywords:

  • antibacterial and antifungal activities of essential oils;
  • methods, for quantifying antimicrobial activity;
  • factors influencing activity - microorganism-related factors;
  • mechanisms of action - membrane and membrane-related actions;
  • other antimicrobial effects - toxins, enzymes and virulence factors;
  • synergy between essential oils - or with other compounds;
  • clinical efficacy of essential oils and components;
  • ketones, commonly encountered ketone essential-oil components - menthone, carvone, pulegone and piperitone;
  • other antimicrobial effects - toxins, enzymes and virulence factors;
  • toxicity of essential oils - ‘natural’, essential oils, far from nontoxic

Summary

Essential oils are bactericidal and fungicidal agents that are typically active at concentrations of 5% or less. Oils rich in aldehydes, phenols or alcohols generally show the greatest antimicrobial activity, since these component groups tend to be the most antimicrobially active. Lethal action is directly related to the solubility of oil components in microbial membranes and disruption of associated functions. More subtle mechanisms such as changes in metabolic or biosynthetic processes or enzyme function have not been investigated to any great extent. However, a range of effects occurring at non-lethal concentrations such as inhibition of virulence, adhesion and biofilm and the up- and down-regulation of numerous genes have been shown. On the basis of these actions, end-use applications such as food and crop preservation and as medicinal agents for humans and domesticated animals have been investigated for a selection of oils. Essential oils have demonstrated clinical efficacy for the treatment of otitis media, dermatophyte infections and oral and vaginal candidiasis in animals in addition to oral and vaginal infections, acne, MRSA colonisation, dandruff, nail infections and tinea in humans. There is therefore broad scope for utilising essential oils as antimicrobial agents in an array of settings, providing that critical issues such as effective delivery systems and potential toxicity to humans and the environment are addressed.