The antimicrobial activity of alpha-bisabolol and tea tree oil against Solobacterium moorei, a Gram-positive bacterium associated with halitosis

Arch Oral Biol. 2013 Jan;58(1):10-6. doi: 10.1016/j.archoralbio.2012.08.001. Epub 2012 Aug 29.


Objective: To investigate the antimicrobial effect of alpha-bisabolol and tea tree oil alone and in combination against the halitosis-associated Gram-positive bacillus Solobacterium moorei.

Design: The inhibitory activity of alpha-bisabolol and tea tree oil against the reference strain S. moorei CCUG39336 and four clinical S. moorei isolates was investigated by a direct exposure test. Additionally, the ability of alpha-bisabolol to increase the sensitivity of S. moorei was tested by pretreating the bacteria with sublethal concentrations prior to the administration of tea tree oil.

Results: A dose-dependent killing was observed for the antimicrobial agents in a direct exposure test with the reference strain S. moorei CCUG39336. Concentrations of ≥0.5% tea tree oil caused decreases in viability of >5 log colony forming units/ml even after short incubation periods, while bacterial viability was less affected by alpha-bisabolol. The combination of 0.1% alpha-bisabolol plus 0.05% tea tree oil showed a synergistic effect on S. moorei strain CCUG39336 and on two of the four clinical S. moorei isolates tested. However, incubation of S. moorei with a sublethal concentration of 0.1% alpha-bisabolol for three days prior to the administration of 0.05% tea tree oil did not enhance the antibacterial effect of tea tree oil.

Conclusion: Halitosis-associated bacterium S. moorei is susceptible to the antimicrobial agents tea tree oil and alpha-bisabolol, suggesting that these compounds might be beneficial in oral healthcare products.

Publication types

  • Comparative Study

MeSH terms

  • Anti-Bacterial Agents / administration & dosage
  • Anti-Bacterial Agents / pharmacology*
  • Anti-Infective Agents, Local / administration & dosage
  • Anti-Infective Agents, Local / pharmacology
  • Bacterial Load / drug effects
  • Chlorhexidine / analogs & derivatives
  • Chlorhexidine / pharmacology
  • Dose-Response Relationship, Drug
  • Drug Combinations
  • Drug Synergism
  • Gram-Positive Bacteria / drug effects*
  • Halitosis / microbiology*
  • Humans
  • Materials Testing
  • Microbial Sensitivity Tests
  • Microbial Viability / drug effects
  • Monocyclic Sesquiterpenes
  • Sesquiterpenes / administration & dosage
  • Sesquiterpenes / pharmacology*
  • Tea Tree Oil / administration & dosage
  • Tea Tree Oil / pharmacology*


  • Anti-Bacterial Agents
  • Anti-Infective Agents, Local
  • Drug Combinations
  • Monocyclic Sesquiterpenes
  • Sesquiterpenes
  • bisabolol
  • Tea Tree Oil
  • chlorhexidine gluconate
  • Chlorhexidine