title: In vitro bactericidal effects of 405-nm and 470-nm blue light.
abstract: OBJECTIVE
  The aim of this study was to determine the bactericidal effect of 405- and 470-nm light on two bacteria, Staphylococcus aureus and Pseudomonas aeruginosa, in vitro.
  
  
  BACKGROUND
  It is well-known that UV light kills bacteria, but the bactericidal effects of UV may not be unique since recent studies indicate that blue light produces a somewhat similar effect. The effects of blue light seem varied depending on wavelength, dose and the nature of the bacteria, hence this study.
  
  
  METHODS
  Two common aerobes, Staphylococcus aureus and Pseudomonas aeruginosa, and anaerobic Propionibacterium acnes were tested. Each organism was treated with Super Luminous Diode probes with peak emission at 405 and 470 nm. Treatment was timed to yield 1, 3, 5, 10, and 15 Jcm2 doses. Colony counts were performed and compared to untreated controls.
  
  
  RESULTS
  The 405-nm light produced a dose dependent bactericidal effect on Pseudomonas aeruginosa and Staphylococcus aureus (p < .05), achieving as much as 95.1% and nearly 90% kill rate for each, respectively. The 470-nm light effectively killed Pseudomonas aeruginosa at all dose levels, but only killed Staphylococcus aureus at 10 and 15 J cm2. With this wavelength, as much as 96.5% and 62% reduction of Pseudomonas aeruginosa and Staphylococcus aureus was achieved, respectively. Neither of the two wavelengths proved bactericidal with anaerobic Propionibacterium acnes.
  
  
  CONCLUSIONS
  The results indicate that, in vitro, 405- and 470-nm blue light produce dose dependent bactericidal effects on Pseudomonas aeruginosa and Staphylococcus aureus but not Propionibacterium acnes.
authors.affiliation: Physical Therapy Plus, Bauxite, Arkansas 72011, USA. drguffey@earthlink.net
authors.forename: J Stephen
authors.initials: JS
authors.lastname: Guffey
authors.forename: Jay
authors.initials: J
authors.lastname: Wilborn
mesh_terms: D015169:Colony Count, Microbial; D006801:Humans; D066298:In Vitro Techniques; D010789:Phototherapy / Q000379:methods*; D011425:Propionibacterium acnes / Q000528:radiation effects*; D011550:Pseudomonas aeruginosa / Q000528:radiation effects*; D013211:Staphylococcus aureus / Q000528:radiation effects*