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Bacteria killing rate in vitro after cross-linking

Session Details

Session Title: Cross-linking

Session Date/Time: Monday 07/10/2013 | 14:30-16:30

Paper Time: 15:02

Venue: Elicium 2 (First Floor)

First Author: : F.Hoogewoud SWITZERLAND

Co Author(s): :    O. Richoz   F. Hafezi           

Abstract Details


To demonstrate the antimicrobial efficacy of corneal crosslinking in vitro and to evaluate three different intensities of treatment.


Infectious corneal ulceration is a common cause of visual loss. The final outcome is influenced by early diagnosis and traditionally by intensive treatment with topical antibiotics. Today, corneal collagen crosslinking (CXL) represents another therapeutic approach; however, the standard protocol (3 mW/cm2 during 30 min) has not been optimized for this new indication. Our study investigates the effect of CXL on two common pathogenic bacteria, meticillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa, at three different power and time settings.


A porous polymer 300 ?m thick, containing 96% of water, not toxic for the bacteria and not UV-absorbing was used as a support for the experiment.  Two solutions of 106 bacteria, one of methicillin-resistant Staphylococcus aureus and one of Pseudomonas aeruginosa, combined with 0.1% Riboflavin solution were instilled in the polymer. Three different protocols of UV-irradiation (365nm) using the same energy (5.4 mJ) at different time and power settings were tested (3 mW/cm2 during 30 min; 9 mW/cm2 during 10 min; 18 mW/cm2 during 5 min). After irradiation, the solution was cultured on a blood agar plate and the CFU (colony forming units) were counted  after 24h of incubation. Controls without riboflavin and with riboflavin but without irradiation were performed.


At the three different power settings, the number of bacteria was reduced by 2 log(10) scales compared with both control groups. No significant differences were detected between the three protocols.


CXL is an efficient bacteriosidal method in vitro.  The killing rate of bacteria is equally high with the three protocols tested suggesting that in clinical practice the time-sparing protocol (18 mW/cm2 during 5 min) should provide as good results as the standard protocol (3 mW/cm2 during 30 min). Clinical trials should be conducted to confirm this hypothesis.

Financial Interest:


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