Abstract
Purpose: :
In a previous work, we have demonstrated the efficacy of riboflavin/UVA light combination as an antimicrobial agent for corneal infections. The purpose of this work is to assess the optimal settings required to achieve antimicrobial activity against common pathogens.
Methods: :
Five isolates (P. aeruginosa, S. aureus, S. epidermidis, Methicillin-Resistant S. aureus - MRSA, and S. pneumoniae) were tested using a modified Kirby-Bauer disks-test in the following fashion: a) control empty discs; b) UV-A exposure alone; c) riboflavin 0.1% /UV-A exposure, and d) "pre-activated" riboflavin 0.1%/UV-A. Exposure time was 15, 20, 25 and 30 min. Mean growth inhibition zone (GIZ) in mm2 was measured around disks. The larger the GIZ, the better the antimicrobial effect.
Results: :
No GIZ was measurable in any of the groups when the UV-A exposure time was 15 minutes in all isolates. Mean GIZ was 47 mm2 (3.64 SD) using "d" for 20 min in S. aureus, S. epidermidis. For P. aeruginosa, the best result was a GIZ of 32 mm2 (3.74 SD) in "d" for 30 min, and for MRSA, a GIZ of 36 mm2 (2.82 SD) in "d" for 25 min.
Conclusions: :
Riboflavin/UV-A with "pre-activated" riboflavin treatment was the most effective approach as antimicrobial therapy. The optimal duration of exposure was 30 min for all pathogens, which seems to be similar to what is currently used in crosslinking studies.
Keywords: cornea: epithelium • keratitis