title: Antibacterial efficacy of accelerated photoactivated chromophore for keratitis-corneal collagen cross-linking (PACK-CXL).
abstract: OBJECTIVE
  To investigate whether optimized photoactivated chromophore for keratitis-corneal collagen cross-linking (PACK-CXL) treatment settings allow accelerating treatment while maintaining antibacterial efficacy.
  
  
  METHODS
  Staphylococcus aureus and Pseudomonas aeruginosa strains were irradiated with ultraviolet-A light of equal fluence but different intensity settings (18 mW/cm² for 5 minutes and 36 mW/cm² for 2.5 minutes). The killing rate was determined by comparing the number of colony-forming units between cross-linked specimens and non-irradiated controls. The potential additional effect of 0.001% benzalkonium chloride was also investigated.
  
  
  RESULTS
  The killing rates for Staphylococcus aureus were 92.5% ± 5.5% (5 minutes at 18 mW/cm²) and 94.4% ± 2.9% (2.5 minutes at 36 mW/cm²). For Pseudomonas aeruginosa, the killing rates were 93.2% ± 8.3% (5 minutes at 18 mW/cm²) and 92.9% ± 5.0% (2.5 minutes at 36 mW/cm²). The presence of benzalkonium chloride in the riboflavin solution did not increase the killing rate significantly.
  
  
  CONCLUSIONS
  The antibacterial efficacy of PACK-CXL follows the Bunsen-Roscoe law of reciprocity and can be maintained even when the irradiation intensity is considerably increased. These optimized settings may allow a shortened treatment time in the future for PACK-CXL and thus help facilitate the transition from the operating room to the slit lamp for treatment.
authors.forename: Olivier
authors.initials: O
authors.lastname: Richoz
authors.forename: Sabine
authors.initials: S
authors.lastname: Kling
authors.forename: Florence
authors.initials: F
authors.lastname: Hoogewoud
authors.forename: Arthur
authors.initials: A
authors.lastname: Hammer
authors.forename: David
authors.initials: D
authors.lastname: Tabibian
authors.forename: Patrice
authors.initials: P
authors.lastname: Francois
authors.forename: Jacques
authors.initials: J
authors.lastname: Schrenzel
authors.forename: Farhad
authors.initials: F
authors.lastname: Hafezi
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology / Q000627:therapeutic use*; D001548:Benzalkonium Compounds / Q000494:pharmacology; D015169:Colony Count, Microbial; D003320:Corneal Ulcer / Q000188:drug therapy* / Q000382:microbiology; D015818:Eye Infections, Bacterial / Q000188:drug therapy* / Q000382:microbiology; D017319:Photosensitizing Agents / Q000627:therapeutic use*; D011552:Pseudomonas Infections / Q000188:drug therapy* / Q000382:microbiology; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000302:isolation & purification / Q000528:radiation effects; D012256:Riboflavin / Q000494:pharmacology / Q000627:therapeutic use*; D013203:Staphylococcal Infections / Q000188:drug therapy* / Q000382:microbiology; D013211:Staphylococcus aureus / Q000187:drug effects / Q000302:isolation & purification / Q000528:radiation effects; D013552:Swine; D014466:Ultraviolet Rays
chemical_list: D000900:Anti-Bacterial Agents; D001548:Benzalkonium Compounds; D017319:Photosensitizing Agents; D012256:Riboflavin