title: Photodynamic UVA-riboflavin bacterial elimination in antibiotic-resistant bacteria.
abstract: BACKGROUND
  To evaluate the bactericidal effect of clinical ultraviolet A (UVA) settings used in photoactivated chromophore for infectious keratitis (PACK)-collagen cross-linking (CXL) in antibiotic-resistant and non-resistant bacterial strains.
  
  
  METHODS
  Well-characterized bacterial strains from clinical isolates, without and with antibiotic resistance, were studied in a pairwise comparison. The evaluated pathogens were Staphylococcus epidermidis, Staphylococcus aureus, Pseudomonas aeruginosa, and Enterococcus faecalis. Bacteria were dispersed in PBS and diluted to a concentration of approximately 4 × 105/ml. Riboflavin was added to a concentration of 0.01%. By spreading the solution on a microscope slide, a fluid film layer, with a thickness of around 400 mm, was formed and UVA exposure followed. Eight separate exposures were made for each strain (n = 8). The degree of elimination in resistant and non-resistant pathogens was compared.
  
  
  RESULTS
  The bactericidal efficacy of exposure differed between the tested microorganisms, and the mean elimination ranged between 60 and 92%, being most extensive in both of the evaluated Pseudomonas strains and least in the E. faecalis strains. Similar reductions were seen in antibiotic-resistant and non-resistant strains, with the exception of S. aureus, in which the resistant strain metchicillin-resistant Staphylococcus aureus (MRSA) was eradicated in a greater extent than the non-resistant strain (P = 0.030).
  
  
  CONCLUSIONS
  UVA-riboflavin settings used in PACK-CXL are effective in reducing both antibiotic-resistant and non-resistant bacteria. Antibiotic resistance does not appear to be protective against the photooxidative exposure.
authors: Department of Ophthalmology, Faculty of Medicine and Health, Örebro University, Örebro, Sweden. karim.makdoumi@regionorebrolan.se.
authors: Karim
authors: K
authors: Makdoumi
authors: Clinical Research Centre, Faculty of Medicine and Health, Örebro University, Örebro, Sweden.
authors: Anders
authors: A
authors: Bäckman
mesh_terms: D001419:Bacteria / Q000187:drug effects* / Q000528:radiation effects*; D015169:Colony Count, Microbial; D003131:Combined Modality Therapy; D024881:Drug Resistance, Bacterial; D013293:Enterococcus faecalis / Q000187:drug effects / Q000528:radiation effects; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000494:pharmacology*; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000528:radiation effects; D012256:Riboflavin / Q000494:pharmacology*; D013211:Staphylococcus aureus / Q000187:drug effects / Q000528:radiation effects; D013212:Staphylococcus epidermidis / Q000187:drug effects / Q000528:radiation effects; D014466:Ultraviolet Rays; D014467:Ultraviolet Therapy
chemical_list: D017319:Photosensitizing Agents; D012256:Riboflavin
keywords: UVA; bacteria; resistance; riboflavin; ultraviolet