Susceptibility of oral bacteria to Melaleuca alternifolia (tea tree) oil in vitro

Authors

  • K. A. Hammer,

    1. Discipline of Microbiology, School of Biomedical and Chemical Sciences, The University of Western Australia, Crawley, Western Australia, Australia,
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  • L. Dry,

    1. Discipline of Microbiology, School of Biomedical and Chemical Sciences, The University of Western Australia, Crawley, Western Australia, Australia,
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  • M. Johnson,

    1. Division of Microbiology and Infectious Diseases, Western Australian Centre for Pathology and Medical Research, Queen Elizabeth ΙΙ Medical Centre, Nedlands, Western Australia, Australia
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  • E. M. Michalak,

    1. Discipline of Microbiology, School of Biomedical and Chemical Sciences, The University of Western Australia, Crawley, Western Australia, Australia,
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  • C. F. Carson,

    1. Discipline of Microbiology, School of Biomedical and Chemical Sciences, The University of Western Australia, Crawley, Western Australia, Australia,
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  • T. V. Riley

    1. Discipline of Microbiology, School of Biomedical and Chemical Sciences, The University of Western Australia, Crawley, Western Australia, Australia,
    2. Division of Microbiology and Infectious Diseases, Western Australian Centre for Pathology and Medical Research, Queen Elizabeth ΙΙ Medical Centre, Nedlands, Western Australia, Australia
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Katherine A. Hammer, Discipline of Microbiology (M502), School of Biomedical and Chemical Sciences, The University of Western Australia, 35 Stirling Hwy, Crawley, Western Australia, 6009, Australia
Tel.: +61 8 9346 4730; fax: +61 8 9346 2912;
e-mail: khammer@cyllene.uwa.edu.au

Abstract

The in vitro activity of Melaleuca alternifolia (tea tree) oil against 161 isolates of oral bacteria from 15 genera was determined. Minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) ranged from 0.003 to 2.0% (v/v). MIC90 values were 1.0% (v/v) for Actinomyces spp., Lactobacillus spp., Streptococcus mitis and Streptococcus sanguis, and 0.1% (v/v) for Prevotella spp. Isolates of Porphyromonas, Prevotella and Veillonella had the lowest MICs and MBCs, and isolates of Streptococcus, Fusobacterium and Lactobacillus had the highest. Time kill studies with Streptococcus mutans and Lactobacillus rhamnosus showed that treatment with ≥0.5% tea tree oil caused decreases in viability of >3 log colony forming units/ml after only 30 s, and viable organisms were not detected after 5 min. These studies indicate that a range of oral bacteria are susceptible to tea tree oil, suggesting that tea tree oil may be of use in oral healthcare products and in the maintenance of oral hygiene.

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