Photodynamic inactivation of pathogens causing infectious keratitis

Abstract

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 cm 2 ). 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.

Chlorin e6 mediated photodynamic inactivation for multidrug resistant Pseudomonas aeruginosa keratitis in mice in vivo

“…Our current study assessed the effectivity of corneal PDI by the photosensitizer Ce6 and red light (λ = 670 nm) against MDR-PA keratitis in a murine infection model. We observed that a single PDI treatment with this photosensitizer/light combination significantly decreased the bacterial load in infected eyes by more than 90% at one h post PDI when Ce6 concentrations of 0.01% and 0.05% were utilized, indicating that this PDI procedure exhibits a bactericidal effect in the mouse cornea in vivo as it does in vitro 41 42 43 44 50 .…”