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Taiichiro Chikama, Kentaro Sueoka, Ji-Ae Ko, Takemasa Sakaguchi, Yoshiaki Kiuchi; Clinical and Histopathologic Evaluation of the Efficacy of Photodynamic Antimicrobial Chemotherapy for Experimental Keratitis. Invest. Ophthalmol. Vis. Sci. 2018;59(9):3660.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the efficacy of photodynamic antimicrobial chemotherapy (PACT) for treatment of infectious keratitis.
We developed a rabbit model of infectious keratitis caused by Staphylococcus aureus. PACT with a cationic chlorin derivative (TONS504; Porphyrin Lab, Okayama, Japan) and a light-emitting diode (LED) device (CCS, Kyoto, Japan) that delivers light at a single wavelength (660 nm) was applied to one cornea of male Japanese white rabbits in vivo. TONS504 was administered at a concentration of 1 mg/mL, and light was delivered at an energy of 30 J/cm2. The antibacterial activity of PACT was assessed with the following treatment groups: (1) three eyes subjected to PACT twice at 6 and 9 h after infection (P2); (2) five eyes subjected to PACT three times at 6, 12, and 24 h after infection (P3); (3) three eyes that received no treatment; (4) three eyes that received TONS504 alone at 6, 12, and 24 h after infection; and (5) three eyes subjected to LED irradiation alone at 6, 12, and 24 h after infection. Corneal stromal opacity, cell infiltration into the cornea, and corneal epithelial defects as revealed by fluorescein staining were all evaluated daily for 6 days after infection by slitlamp microscopy. The rabbits were then killed for histopathologic analysis of the infected cornea.
Slitlamp examination revealed that all nine eyes in the three control groups developed severe infectious keratitis by 24 h after bacterial exposure. All three eyes in the P2 group started to manifest signs of infection by 48 h after bacterial exposure. In contrast, the extents of stromal opacity and cell infiltration in four of the five eyes in the P3 group were markedly reduced compared with those in the other groups for up to 6 days. Histopathologic evaluation revealed a thickened cornea with a large number of infiltrating neutrophils and disordered collagen fibers in the stroma for the eyes in both the three control groups and the P2 treatment group. In contrast, four of the five corneas in the P3 treatment group were of almost normal thickness and showed a smaller number of infiltrating neutrophils and regular alignment of stromal collagen fibers.
PACT with TONS504 attenuated the development of corneal infection with S. aureus in a rabbit model in vivo, with repeated application of PACT improving its efficacy.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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