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2021 OMIG Abstract
Evaluation of a Clinical Grade Rose Bengal for
Photodynamic Antimicrobial Therapy
Katherine D. Leviste1, Paula A. Sepulveda-Beltran1, Heather Durkee1, Keenan Mintz3, Braulio Ferreira3, Esdras Arrieta1, Roger Leblanc3, Jean-Marie Parel1,4, Darlene Miller4,5, Guillermo Amescua1,4
1Ophthalmic Biophysics Center, Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida; 2 Department of Biomedical Engineering, College of Engineering, University of Miami, Coral Gables, Florida; 3Department of Chemistry, College of Arts and Science, University of Miami, Coral Gables, Florida; 4Anne Bates Leach Eye Hospital, Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida; 5Ocular Microbiology Laboratory, Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida
Purpose: To evaluate the efficacy of a clinical grade Rose Bengal (RB) photosensitizer on ocular Candida spp. isolates treated with photodynamic antimicrobial therapy (PDAT).
Methods: Two Candida albicans and two Candida parapsilosis isolates were tested in (1) 0.9% NaCl, (2) 0.1% research grade Rose Bengal (RB-1) and (3) 0.1% clinical grade Rose Bengal (RB-2) solutions. 1 mL aliquots of fungal concentrations at 1.5 × 107 CFU/mL were plated on Sabourad-Dextrose plates in triplicate. The following treatment groups were assigned: (1) Control (No photosensitizer/ No Irradiation); (2) Photosensitizer/No Irradiation; (3) Photosensitizer/Irradiation. Group 3 was irradiated with a custom green-light source for 15 minutes at 5.4 J/cm2. Plates were protected from light, incubated at 37℃ for 72 hours, then photographed. Spatial analysis of percent inhibition is in progress using ImageJ software, and an independent t-test will be performed for statistical analysis. In a separate experiment, the inert fungicidal activity of RB mediums on Candida spp. was evaluated and compared to Tryptic Soy Broth (TSB), NaCl controls. The rate of colony proliferation in solution was analyzed by optical densitometry over 7 days.
Results: There was significant growth inhibition of all Candida spp. strains in the groups exposed to RB-PDAT. No inhibitory effect was seen in the groups that did not receive RB-PDAT. Growth curve analysis of Candida spp. showed the beginning of the log growth phase at 6 hours of incubation in their preferred medium. CA-1 did not proliferate, unlike CA-2, CP-1, and CP-2 strains which started their exponential growth at 6 hours of incubation in RB-1 and RB-2 solutions. The presence of RB may have suppressed isolate growth when compared to control, with CA-1 reaching 2x optical density (OD) in preferred TSB medium (400→800 OD), CA-2 3x (400→1200 OD with a peak at 96 hours), CP-1 3x (400→1200 OD plateaued at 48 hours), CP-2 3x (400→1200 OD plateaued at 96 hours). The slopes of colony growth during the log phase was highly congruent between experimental RB-1 and RB-2 suspensions, with no growth observed in CA-1, 1.75x, 2x, >2x average OD growth between RB-1 and RB-2 mediums for CA-2, CP-1, and CP-2, respectively. Proliferation susceptibility appears to be strain-dependent among Candida spp. grown in RB suspension without PDAT.
Conclusions: There was comparable efficacy and no significant difference between research grade RB-1 and clinical grade RB-2 when combined with PDAT inhibit the growth of Candida spp. isolates in vitro. RB-PDAT may be an effective adjunct treatment for Candida spp. infections.
Disclosure: N (KDL, PSB, KM, BF, EA, RL, DM; P (HD, JMP, GA)
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