title: Preliminary assessment of photoactivated antimicrobial collagen on bioburden in a murine pressure ulcer model.
abstract: OBJECTIVE
  Overcoming bacterial antibiotic resistance requires alternative strategies. The ability of photoactivated collagen-embedded flavins (PCF) to reduce bioburden in infected pressure ulcers was investigated.
  
  
  METHODS
  Two pressure ulcers were created on the dorsum of female BALB/C mice (n=40, 35 g) maintaining a 5 mm skin bridge between lesions. Ulcers and surrounding skin were covered with Tegaderm™ and inoculated with 0.1 mL of 1 × 10(5) colony-forming units (CFU)/mL methicillin-resistant Staphylococcus aureus (MRSA). Fluid was permitted to reabsorb for 10 min. In experiment 1, one wound from each animal was treated using PCF and photoradiation (PCF+R, n=12) or photoradiation alone (R, n=11). Composite dressing-treated wounds received 1 × 1 cm PCF discs. Overlying Tegaderm was excised, and PCF was placed over the wound and again covered with Tegaderm. Wounds were irradiated at 455 ± 5 nm (350 mW, 1 cm spot diameter, 15 min) using a diode laser 10 min after placement. Controls received no PCF or photoradiation (C, n=12). Animals were euthanized 24 h post-therapy. Quantitative bacterial counts (CFU/g tissue) were determined. In experiment 2, composite dressing-treated wounds were irradiated at 455 ± 5 nm (350 mW, 1 cm spot diameter, 15 min) using a diode laser 10 min after daily PCF placement (0, 1, 2, or 3 treatments, n=8/group). Controls received no treatment. Wounds were cultured daily. Animals were euthanized on day 7 post-infection. Quantitative bacterial counts were determined.
  
  
  RESULTS
  PCF+R significantly reduced bacterial counts at 24 h (experiment 1, p<0.0001; experiment 2, p<0.05). The bacterial counts in rats receiving photoradiation alone were no different from those of untreated controls (experiment 1, p=0.24). PCF+R produced a 2-3 log reduction in bacterial counts (experiment 2, p<0.001). Antibacterial effects increased with number of treatments, and persisted for several days post-therapy (p<0.002).
  
  
  CONCLUSIONS
  PCF+R inhibited bacterial growth in this model. This effect increased with successive treatments, persisting several days post-therapy. Further studies to optimize this treatment modality are warranted.
authors.affiliation: 1 Raymond J. Lanzafame, MD, PLLC , Rochester, New York.
authors.forename: Raymond J
authors.initials: RJ
authors.lastname: Lanzafame
authors.forename: Istvan
authors.initials: I
authors.lastname: Stadler
authors.forename: Ryan
authors.initials: R
authors.lastname: Cunningham
authors.forename: Aaron
authors.initials: A
authors.lastname: Muhlbauer
authors.forename: Jacob
authors.initials: J
authors.lastname: Griggs
authors.forename: Robert
authors.initials: R
authors.lastname: Soltz
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Soltz
mesh_terms: D000818:Animals; D003094:Collagen / Q000494:pharmacology* / Q000528:radiation effects; D015169:Colony Count, Microbial; D005260:Female; D005415:Flavins / Q000494:pharmacology*; D055624:Methicillin-Resistant Staphylococcus aureus; D008807:Mice, Inbred BALB C; D009779:Occlusive Dressings; D010778:Photochemotherapy / Q000379:methods*; D003668:Pressure Ulcer / Q000382:microbiology* / Q000628:therapy*; D013203:Staphylococcal Infections / Q000188:drug therapy*
chemical_list: D005415:Flavins; D003094:Collagen