title: The effects of nitric oxide on Staphylococcus aureus biofilm growth and its implications in chronic rhinosinusitis.
abstract: BACKGROUND
  The relationship between sinonasal nitric oxide (NO) levels and the pathogenic organism Staphylococcus aureus is yet to be established. High NO levels measured in healthy sinuses likely contribute to maintenance of relative sterility. Lower concentrations such as is found in the sinuses of chronic rhinosinusitis (CRS) patients may decrease this effect. S. aureus in biofilm form has recently been implicated in recalcitrant CRS, its isolation predicting a higher risk of posttreatment reinfection. This in vitro study aims to characterize the changes in S. aureus biofilm formation when exposed to different NO levels mimicking the normal and diseased NO sinus concentrations reported in previous literature in an in vitro setting.
  
  
  METHODS
  S. aureus ATCC 25923 and 7 clinical isolates were cultured in biofilm form using the MBEC device and the established biofilms exposed to 1 to 1000 μM NO concentrations. Biofilms were visualized using Live/Dead Baclight stain and confocal scanning laser microscopy, and quantified using Comstat2, a biofilm quantification software.
  
  
  RESULTS
  Biofilm biomass decreases from an average of 0.105 to 0.057 μm(3) /μm(2) at higher NO concentrations (125-1000 μM), but is increased to 0.470 μm(3) /μm(2) at lower NO concentrations (0.9-2.0 μM). The average biomass at high vs low concentrations are statistically significant (p < 0.001).
  
  
  CONCLUSIONS
  S. aureus biofilm formation varies across exposure to different NO levels, with antibiofilm effects at higher concentrations, and enhanced biofilm formation at lower or subphysiologic concentrations. These results coincide with the often dualistic function of NO, and have implications in its future use in the treatment of CRS.
authors.affiliation: Department of Surgery-Otorhinolaryngology Head and Neck Surgery, The Queen Elizabeth Hospital, and the University of Adelaide, Adelaide, South Australia.
authors.forename: Camille
authors.initials: C
authors.lastname: Jardeleza
authors.forename: Andrew
authors.initials: A
authors.lastname: Foreman
authors.forename: Leonie
authors.initials: L
authors.lastname: Baker
authors.forename: Sathish
authors.initials: S
authors.lastname: Paramasivan
authors.forename: John
authors.initials: J
authors.lastname: Field
authors.forename: Lor Wai
authors.initials: LW
authors.lastname: Tan
authors.forename: Peter-John
authors.initials: PJ
authors.lastname: Wormald
mesh_terms: D018441:Biofilms / Q000187:drug effects*; D002908:Chronic Disease; D006801:Humans; D009569:Nitric Oxide / Q000008:administration & dosage / Q000494:pharmacology*; D012220:Rhinitis / Q000188:drug therapy*; D012852:Sinusitis / Q000188:drug therapy*; D013203:Staphylococcal Infections / Q000188:drug therapy; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000502:physiology
chemical_list: D009569:Nitric Oxide