title: The bactericidal effect of 470-nm light and hyperbaric oxygen on methicillin-resistant Staphylococcus aureus (MRSA).
abstract: It has been shown that, in vitro, hyperbaric oxygen (HBO) suppresses 28 % bacterial growth, while 470-nm blue light alone suppresses up to 92 % methicillin-resistant Staphylococcus aureus (MRSA) in one application in vitro. Therefore, we determined if combined 470-nm light (55 J/cm(2)) and HBO will yield 100 % bacterial suppression in experimental simulation of mild, moderate or severe MRSA infection. We cultured MRSA at 3 × 10(6), 5 × 10(6), 7 × 10(6), 8 × 10(6), or 12 × 10(6) CFU/ml and treated each concentration in four groups as follows: (1) control (no treatment) (2) photo-irradiation only, (3) photo-irradiation then HBO, (4) HBO only, and (5) HBO then photo-irradiation. Bacteria colonies were then quantified. The results showed that at each bacterial concentration, HBO alone was significantly less effective in suppressing MRSA than photo-irradiation or combined HBO and photo-irradiation (p < 0.0001). Similarly, at no bacterial concentration did combined HBO and 470-nm light treatment yield a statistically better result than 470-nm light alone (p > 0.05), neither did HBO treatment either before or after irradiation make a difference. Furthermore, at no bacterial concentration was 100 % MRSA suppression achieved. Indeed, the maximum bacterial suppression attained was in the mild infection model (3 × 10(6) CFU/ml), with blue light producing 97.3 ± 0.2 % suppression and HBO + 55 J/cm(2) yielding 97.5 ± 2.5 % suppression. We conclude that (1) HBO and 470-nm light individually suppress MRSA growth; (2) 470-nm blue light is more effective in suppressing MRSA than HBO; and (3) HBO did not act synergistically to heighten the bactericidal effect of 470-nm light.
authors.affiliation: College of Health Sciences, University of Wisconsin-Milwaukee, 2400 East Hartford Avenue, Milwaukee, WI, 53211, USA.
authors.forename: Violet Vakunseh
authors.initials: VV
authors.lastname: Bumah
authors.forename: Harry Thomas
authors.initials: HT
authors.lastname: Whelan
authors.forename: Daniela Santos
authors.initials: DS
authors.lastname: Masson-Meyers
authors.forename: Brendan
authors.initials: B
authors.lastname: Quirk
authors.forename: Ellen
authors.initials: E
authors.lastname: Buchmann
authors.forename: Chukuka Samuel
authors.initials: CS
authors.lastname: Enwemeka
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D008027:Light; D055624:Methicillin-Resistant Staphylococcus aureus / Q000502:physiology / Q000528:radiation effects*; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability; D010100:Oxygen / Q000494:pharmacology*; D011312:Pressure
chemical_list: D000900:Anti-Bacterial Agents; D010100:Oxygen