title: Inhibition of quorum sensing regulated bacterial functions by plant essential oils with special reference to clove oil.
abstract: OBJECTIVE
  To evaluate quorum sensing (QS) inhibitory activity of plant essential oils using strains of Chromobacterium violaceum (CV12472 and CVO26) and Pseudomonas aeruginosa (PAO1).
  
  
  RESULTS
  Inhibition of QS-controlled violacein production in C. violaceum was assayed using disc diffusion and agar well diffusion method. Of the 21 essential oils, four oils showed varying levels of anti-QS activity. Syzygium aromaticum (Clove) oil showed promising anti-QS activity on both wild and mutant strains with zones of pigment inhibition 19 and 17 mm, respectively, followed by activity in cinnamon, lavender and peppermint oils. The effect of clove oil on the extent of violacein production was estimated photometrically and found to be concentration dependent. At sub-MICs of clove oil, 78.4% reduction in violacein production over control and up to 78% reduction in swarming motility in PAO1 over control were recorded. Gas chromatography-mass spectrometry analysis of clove oil indicated presence of many phytocompounds. Eugenol, the major constituent of clove oil could not exhibit anti-QS activity.
  
  
  CONCLUSIONS
  Presence of anti-QS activity in clove oil and other essential oils has indicated new anti-infective activity. The identification of anti-QS phytoconstituents is needed to assess the mechanism of action against both C. violaceum and Ps. aeruginosa.
  
  
  CONCLUSIONS
  Essential oils having new antipathogenic drugs principle because of its anti-QS activity might be important in reducing virulence and pathogenicity of drug-resistant bacteria in vivo.
authors.affiliation: Department of Agricultural Microbiology, Faculty of Agricultural Sciences, Aligarh Muslim University, Aligarh, India.
authors.forename: M S A
authors.initials: MS
authors.lastname: Khan
authors.forename: M
authors.initials: M
authors.lastname: Zahin
authors.forename: S
authors.initials: S
authors.lastname: Hasan
authors.forename: F M
authors.initials: FM
authors.lastname: Husain
authors.forename: I
authors.initials: I
authors.lastname: Ahmad
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002861:Chromobacterium / Q000187:drug effects / Q000502:physiology*; D045783:Clove Oil / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D008401:Gas Chromatography-Mass Spectrometry; D007211:Indoles / Q000378:metabolism; D008124:Locomotion / Q000187:drug effects; D009822:Oils, Volatile / Q000302:isolation & purification / Q000494:pharmacology*; D010944:Plants / Q000737:chemistry*; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000502:physiology*; D053038:Quorum Sensing / Q000187:drug effects*
chemical_list: D000900:Anti-Bacterial Agents; D045783:Clove Oil; D007211:Indoles; D009822:Oils, Volatile; C063155:violacein