Abstract:
Background: A prototype solid-state Ultraviolet-C device may be useful in the treatment of corneal microbial infections, as Ultraviolet-C is commonly used for eradicating microbes in other settings. This study assessed the efficacy of a 265nm Ultraviolet-C device on four bacterial strains, and investigated the consequences of corresponding exposures on human corneal epithelial cells in vitro. Design: Prospective university-based in vitro interventional controlled study. Samples: Agar plate lawns of Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Streptococcus pyogenes, and human corneal epithelial cells cultured on glass cover slips. Methods: Bacterial plates and human corneal epithelial cultures were exposed to a 4.5mm diameter 265nm beam at a fixed intensity and distance, for 30, 5, 4, 2 and 1 seconds, with four repeated measures at each exposure. Main Outcome Measures: Bacterial growth inhibition was assessed with a BioRad Gel imager, and the diameter of lucent areas recorded. Live/dead staining was quantified for exposed corneal epithelium. Results: There was 100% inhibition of growth for all bacteria tested, at all exposure times. Human corneal epithelium 30-second exposure versus no exposure (control), showed no difference in the ratio of live-to-dead cells (p = 0.877). Conclusions: The results confirmed that a 1-second exposure to germicidal Ultraviolet-C was sufficient to inhibit microbial proliferation in the four bacterial strains tested in vitro. Combined with the large safety margin established for human corneal epithelium exposed to Ultraviolet-C, the results suggest that low dose Ultraviolet-C could potentially be beneficial in treating corneal surface infections.