14 April 2014 Photodynamic inactivation of pathogens causing infectious keratitis
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The increasing prevalence of antibiotic resistance requires new approaches also for the treatment of infectious keratitis. Photodynamic Inactivation (PDI) using the photosensitizer (PS) Chlorin e6 (Ce6) was investigated as an alternative to antibiotic treatment. An in-vitro cornea model was established using porcine eyes. The uptake of Ce6 by bacteria and the diffusion of the PS in the individual layers of corneal tissue were investigated by fluorescence. After removal of the cornea’s epithelium Ce6-concentrations < 1 mM were sufficient to reach a penetration depth of 500 μm. Liquid cultures of microorganisms were irradiated using a specially constructed illumination chamber made of Spectralon(R) (reflectance: 99 %), which was equipped with high power light emitting diodes (λ = 670 nm). Clinical isolates of Staphylococcus aureus (SA) and Pseudomonas aeruginosa (PA) from keratitis patients were tested in liquid culture against different concentrations of Ce6 (1 - 512 μM) using 10 minutes irradiation (E = 18 J/cm2 ). This demonstrated that a complete inactivation of the pathogen strains were feasible whereby SA was slightly more susceptible than PA. 3909 mutants of the Keio collection of Escherichia coli (E.coli) were screened for potential resistance factors. The sensitive mutants can be grouped into three categories: transport mutants, mutants in lipopolysaccharide synthesis and mutants in the bacterial SOS-response. In conclusion PDI is seen as a promising therapy concept for infectious keratitis.
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Carole Simon, Carole Simon, G. Wolf, G. Wolf, M. Walther, M. Walther, K. Winkler, K. Winkler, M. Finke, M. Finke, D. Hüttenberger, D. Hüttenberger, Markus Bischoff, Markus Bischoff, B. Seitz, B. Seitz, J. Cullum, J. Cullum, H.-J. Foth, H.-J. Foth, "Photodynamic inactivation of pathogens causing infectious keratitis", Proc. SPIE 8931, Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy XXIII, 89310T (14 April 2014); doi: 10.1117/12.2037704; https://doi.org/10.1117/12.2037704

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