title: Evaluation of antibacterial efficacy of photo-activated riboflavin using ultraviolet light (UVA).
abstract: BACKGROUND
  To evaluate the antibacterial efficacy of photo-activated riboflavin using Ultraviolet A (UVA) on three bacterial strains commonly detected in keratitis.
  
  
  METHODS
  Three bacterial strains (Staphylococcus epidermidis, Staphylococcus aureus and Pseudomonas aeruginosa) were cultured on blood/hematin-agar plates and dispersed in PBS. Dispersion was done of 10 microl of bacterial stock-solutions in 90 microl of RPMI, where different riboflavin molarities had been added, to achieve a bacterial concentration of 1-4 x 10 (4)/ml. Riboflavin end molarities before illumination were 0, 100, 200, 300 and 400 microM. Each solution had a negative control. The solutions were illuminated with UVA (365 nm) for 30 minutes (5.4 J/cm(2)) and then continued for a total time of 60 minutes (10.8 J/cm(2)). A count of CFU was conducted after incubation and results compared.
  
  
  RESULTS
  In all tested strains, a slight decrease of bacteria was seen when exposed to UV for 30 minutes. A doubling of the UV dose showed a marked decrease of bacterial count in all bacteria tested. The combination of UV and riboflavin showed a more extensive reduction of CFU, confirming an interaction effect between UV and riboflavin.
  
  
  CONCLUSIONS
  Riboflavin photo-activation using UVA (365 nm) can achieve an extensive eradication of bacteria, and the combination is more potent in reducing bacterial number than UV alone.
authors.affiliation: Department of Ophthalmology, Orebro University Hospital, Orebro, Sweden. karim.makdoumi@orebroll.se
authors.forename: Karim
authors.initials: K
authors.lastname: Makdoumi
authors.forename: Anders
authors.initials: A
authors.lastname: Bäckman
authors.forename: Jes
authors.initials: J
authors.lastname: Mortensen
authors.forename: Sven
authors.initials: S
authors.lastname: Crafoord
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D015169:Colony Count, Microbial; D006801:Humans; D007634:Keratitis / Q000188:drug therapy / Q000382:microbiology*; D017319:Photosensitizing Agents / Q000494:pharmacology*; D011552:Pseudomonas Infections / Q000188:drug therapy / Q000382:microbiology; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000528:radiation effects; D012256:Riboflavin / Q000494:pharmacology*; D013203:Staphylococcal Infections / Q000188:drug therapy / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000187:drug effects / Q000528:radiation effects; D013212:Staphylococcus epidermidis / Q000187:drug effects* / Q000528:radiation effects*; D014466:Ultraviolet Rays
chemical_list: D000900:Anti-Bacterial Agents; D017319:Photosensitizing Agents; D012256:Riboflavin