title: The antimicrobial activity of alpha-bisabolol and tea tree oil against Solobacterium moorei, a Gram-positive bacterium associated with halitosis.
abstract: 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.
  
  
  METHODS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Institute of Preventive Dentistry and Oral Microbiology, School of Dental Medicine, University of Basel, Basel, Switzerland.
authors.forename: Marcel
authors.initials: M
authors.lastname: Forrer
authors.forename: Eva M
authors.initials: EM
authors.lastname: Kulik
authors.forename: Andreas
authors.initials: A
authors.lastname: Filippi
authors.forename: Tuomas
authors.initials: T
authors.lastname: Waltimo
mesh_terms: D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000494:pharmacology*; D000891:Anti-Infective Agents, Local / Q000008:administration & dosage / Q000494:pharmacology; D058491:Bacterial Load / Q000187:drug effects; D002710:Chlorhexidine / Q000031:analogs & derivatives / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D004357:Drug Synergism; D006094:Gram-Positive Bacteria / Q000187:drug effects*; D006209:Halitosis / Q000382:microbiology*; D006801:Humans; D008422:Materials Testing; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability / Q000187:drug effects; D000081222:Monocyclic Sesquiterpenes; D012717:Sesquiterpenes / Q000008:administration & dosage / Q000494:pharmacology*; D020947:Tea Tree Oil / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D000891:Anti-Infective Agents, Local; D004338:Drug Combinations; D000081222:Monocyclic Sesquiterpenes; D012717:Sesquiterpenes; C004497:bisabolol; D020947:Tea Tree Oil; C010882:chlorhexidine gluconate; D002710:Chlorhexidine