Frequencies of resistance to Melaleuca alternifolia (tea tree) oil and rifampicin in Staphylococcus aureus, Staphylococcus epidermidis and Enterococcus faecalis

Int J Antimicrob Agents. 2008 Aug;32(2):170-3. doi: 10.1016/j.ijantimicag.2008.03.013. Epub 2008 Jun 20.


This study was conducted to determine the frequencies at which single-step mutants resistant to tea tree oil and rifampicin occurred amongst the Gram-positive organisms Staphylococcus aureus, Staphylococcus epidermidis and Enterococcus faecalis. For tea tree oil, resistance frequencies were very low at <10(-9). Single-step mutants resistant to tea tree oil were undetectable at two times the minimum inhibitory concentration (MIC) for S. aureus RN4220 and derivative mutator strains or at 3 x MIC for the remaining S. aureus strains, including a clinical meticillin-resistant S. aureus isolate. Similarly, no mutants were recovered at 2x MIC for S. epidermidis or at 1x MIC for E. faecalis. Resistance frequencies determined in vitro for rifampicin (8 x MIC) ranged from 10(-7) to 10(-8) for all isolates, with the exception of the S. aureus mutator strains, which had slightly higher frequencies. These data suggest that Gram-positive organisms such as Staphylococcus and Enterococcus spp. have very low frequencies of resistance to tea tree oil.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / pharmacology*
  • Drug Resistance, Bacterial* / genetics
  • Enterococcus faecalis / drug effects
  • Enterococcus faecalis / genetics
  • Gram-Positive Cocci / drug effects*
  • Gram-Positive Cocci / genetics
  • Humans
  • Melaleuca / chemistry
  • Microbial Sensitivity Tests
  • Mutation
  • Rifampin / pharmacology*
  • Staphylococcus aureus / drug effects
  • Staphylococcus aureus / genetics
  • Staphylococcus epidermidis / drug effects
  • Staphylococcus epidermidis / genetics
  • Tea Tree Oil / pharmacology*


  • Anti-Bacterial Agents
  • Tea Tree Oil
  • Rifampin