Rose Bengal-Mediated Photodynamic Antimicrobial Treatment of Acanthamoeba Keratitis

ABSTRACT

Purpose: To evaluate the in vivo efficacy of rose bengal (RB)-mediated photodynamic antimicrobial therapy (PDAT) for treatment of Acanthamoeba castellanii keratitis (AK).

Materials and Methods: An animal (rabbit) AK model was successfully achieved via intrastromal inoculation of a suspension of A. castellanii cells and trophozoites. Prior to RB-PDAT (pre-treatment, day-5), the severity of the induced corneal infection was graded numerically for epithelial defects, stromal edema, neovascularity, and stromal opacity/infiltration. The right eyes of rabbits (n = 18) were divided equally into three groups (n = 6/group): control (no treatment); 0.1% RB+518 nm irradiation (5.4 J/cm²); and 0.2% RB+518 nm irradiation (5.4 J/cm²). On post-treatment day-5, animals were euthanized, after which corneal buttons were excised and submitted for real-time polymerase chain reaction (RT-PCR) analysis.

Results: Post-treatment clinical scores of the 0.1 and 0.2% RB groups indicated significant improvement compared to control group scores (pre-treatment clinical scores; 5.17 ± 0.98, 7.50 ± 0.62, and 6.17 ± 0.70 and post-treatment clinical scores; 4.50 ± 0.56, (p = .043), 3.50 ± 0.99 (p = .039), 6.83 ± 1.66 (p = .34), respectively). RT-PCR analysis revealed that the mean cycle threshold (Ct) values were significantly higher in treated-group corneas compared to control-group corneas, with no significant differences between treated-groups (Mean Ct values; 34.33, 34.5, and 29.67 for 0.1 and 0.2% RB, and control groups). There was a statistically significant negative correlation between post-treatment clinical scores and Ct values (r = −0.474, p-value 0.047).

Conclusions: Our results demonstrate that RB-PDAT is effective in decreasing the parasitic load and clinical severity of AK.

KEYWORDS:

• Rose Bengal (RB)
• 0.1% and 0.2% RB
• RB-mediated photodynamic antimicrobial therapy (RB-PDAT)
• Acanthamoeba castellanii keratitis

Acknowledgments

We are thankful to Professor Zübeyde Akın Polat, Department of Medical Parasitology, School of Medicine, Cumhuriyet University, Sivas, Turkey, for providing the A. castellanii T4 genotype strain.

Declaration of interest

No conflict of interest is reported by the author(s).