Treatment of Keratitis? A Modell For The Possibility To Evaluate Bacterial Eradication Using UVA + Riboflavin(B2)

Purpose

To evaluate bacterial eradication using UVA + Riboflavin(B2) used in Collagen Cross-Linking.

Methods

See Fig 1

S. epidermidis(ATCC 12228)were cultured, counted and suspended  to approx. 2 x 104/mL in Riboflavin(B2). The 100 mL mixture were placed in sterile cork creating a layer of about 8.5 mm wide and 1.76 mm thick. This was exposed to UVA (365nm), for 0, 30 and 60 minutes, at 5 cm distance using an UV-XTM (Peschke Meditrade, Switzerland).
After each exposure, 10 mL were withdrawn and diluted 1/10 in PBS and plated onto blood-agar plates for CFU-counts.
Every solution had a non-illuminated negative control. All experiments were performed in triplicates and results were analysed statistically by unpaired t-test.

Results

See Fig 2
Almost complete eradication(approx. 83 %) was achived using B2 at 500 uM and UVA for 60 minutes(10.8 J/m2).
At higher concentrations of B2,  the eradication was only around 40-60%.
The thickness of the reaction-fluid could influence the UVA-exposure time for eradication as well as high B2-concentrations.
Controls were significantly different. Increased UVA-dose was more efficient then higher B2-koncentration.

Conclusions

The UVA/B2 combination used in Collagen Cross-Linking can eradicate bacteria in fluid solutions.

The combined effect was more efficient than UVA alone.
The variations of B2- concentration seems to be of importance for the degree of bacterial reduction and a rather low dose seemed to be more efficient than a higher one.
Excess B2 might inhibit UVA penetration, thus reducing antibacterial effect.

This experimental exposure-model for possible treatment of keratitis, could be used to examine the possible eradication of other bacteria using UVA and B2.