Ocular Microbiology and Immunology Group
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2024 OMIG Abstract

Rose Bengal Photodynamic Therapy (PDAT) for Mycobacterium abscessus Keratitis: In Vitro Efficacy and Clinical Outcomes

Salomon Merikansky³, Nhon Le³, Heather Durkee¹, Brandon Chou¹,Juan Carlos Navia¹, Alexander Alfonso², Jorge Maestre², Guillermo Amescua^1-3, Darlene Miller², Jean Marie Parel<sup>2

1</sup>Ophthalmic Biophysics Center, University of Miami Health System Bascom Palmer Eye Institute, Miami, FL; ²Ocular Microbiology Laboratory, University of Miami Health System Bascom Palmer Eye Institute, Miami, FL; ³Ophthalmology, University of Miami Health System Bascom Palmer Eye Institute, Miami, FL

Purpose: Evaluate the efficacy of RB PDAT to inhibit Mycobacterium abscessus clinical strains. The clinical outcomes of seven patients with culture proven Mycobacterium abscessus keratitis who underwent RB-PDAT are also presented.

Methods: In vitro: Five clinical isolates (Mycobacteria abscessus) were isolated and prepared in NaCl for a final concentration of 1.5 x10*8 CFU/mL. Isolates were tested against five experimental groups: (1) no photosensitizer/no irradiation, (2) photosensitizer/no irradiation, (3) photosensitizer/irradiation (6mW), (3) photosensitizer/irradiation(12mW), and (3) photosensitizer/irradiation(18mW). Each isolate was prepared in suspension to a concentration of 1.5 x10*8 CFU/mL. Bacterial suspensions were mixed with water or prepared 0.1% rose bengal solution for a final bacterial concentration of 1.5 x10*7 CFU/mL. Aliquots of 1 mL were plated on 5% sheep blood agar in triplicate. Plates were further separated into three groups based on light intensity (6, 12, 18 mW) and energy (5.4, 10.8, 16.2 J/cm2) irradiated with a custom-made LED green (518nm) light for 15 minutes. Plates were incubated for 48 hours and then photographed to quantify percent inhibition using ImageJ software. Clinical: Charts of seven patients with culture-positive Mycobacterium abscessus isolates who underwent treatment with RB-PDT were reviewed to qualify the disease curse and clinical outcomes

Results: In vitro: Growth inhibition to RB PDAT was strain dependent. Minimal inhibition was observed in the 5.4 J/cm2 fluence group as compared to the 10.8 and 16.2 J/cm2 fluence groups. No inhibition was observed in the rose bengal dark group. Clinical: Mycobacterium abscessus was isolated in all clinical samples. Most common risk factor was prior ocular surgery. Resolution of the infection was observed in 5 of the 7 patients. All eyes required one surgery and the mean time of infection resolution after RB-PDAT was 46 days. Only one eye required a second RB-PDAT for resolution. Two eyes were enucleated.

Conclusions: These in vitro results show greater growth inhibition with increased fluence of green light with RB-PDAT. On the clinical setting, resolution of the infection was observed in the majority of patients, especially when treated promptly. RB-PDAT is a feasible option to halt the progression of non-tuberculoid mycobacteria and could halt the need of enucleation. Higher fluence RB-PDAT should be explored as well as higher concentration of rose bengal to treat these recalcitrant strains of Mycobacterium abscessus. Nonetheless, further safety studies are crucial to assess the potential impacts of green light exposure on the cornea.


Disclosure:

N (SM, NL, BC, JCN, AA, JM); P (HD, DM, JMP, GA)