Hammer KA, Carson CF, Riley TV
American Journal of Infection Control, 1996
The purpose of this study was to determine the susceptibility of a range of transient and commensal skin flora to the essential oil of Melaleuca alternifolia, or tea tree.
A modified broth microdilution method was used. Polyoxyethylene sorbitan mono-oleate detergent was added to the test medium to enhance solubility of the tea tree oil.
Serratia marcescens had the lowest minimum inhibitory concentration (MIC90) of 0.25%. The highest MIC90 was 3% for Pseudomonas aeruginosa. The lowest minimum bactericidal concentration (MBC90) was 0.25% for S. marcescens and Klebsiella pneumoniae, whereas the highest was 8% for Staphylococcus capitis.
S. aureus and most of the gram-negative bacteria tested were more susceptible to tea tree oil than the coagulase-negative staphylococci and micrococci. These results suggest that tea tree oil may be useful in removing transient skin flora while suppressing but maintaining resident flora.
Hammer KA, Carson CF, Riley TV. Susceptibility of transient and commensal skin flora to the essential oil of Melaleuca alternifolia (tea tree oil). Am J Infect Control. 1996;24(3):186-189.