Rose Bengal and Riboflavin Mediated Photodynamic Antimicrobial Therapy Against Selected South Florida Nocardia Keratitis Isolates.

Abstract

Purpose:

To examine and compare the efficacy of in vitro growth inhibition using rose bengal and riboflavin photodynamic antimicrobial therapy (PDAT) for Nocardia keratitis isolates.

Methods:

Nocardia asteroides complex, Nocardia amikacinitolerans, and Nocardia farcinica species were isolated from patients with confirmed Nocardia keratitis. Isolates were tested against three experimental groups: (1) no photosensitizer/no irradiation, (2) photosensitizer/no irradiation, and (3) photosensitizer/irradiation. Each isolate was prepared in suspension to a concentration of 1.5 × 108 CFU/mL. Bacterial suspensions were mixed with water or prepared 0.1% photosensitizer solution for a final bacterial concentration of 1.5 × 107 CFU/mL. Aliquots of 1 mL were plated on 5% sheep blood agar. Rose bengal and riboflavin PDAT plates were irradiated for 15 minutes with a 525- or 375-nm custom 6-mW/cm2 powered light source for a total fluence of 5.4 J/cm2. All experimental groups were repeated in triplicate. Plates were incubated in a 35°C non-CO2 incubator for 96 hours and photographed. Percent inhibition was evaluated using LabVIEW-based software.

Results:

All strains of Nocardia tested with 0.1% rose bengal and irradiated for 15 minutes demonstrated statistically significant inhibition of growth (P < 0.05). No other experimental groups displayed any bacterial inhibition.

Conclusions:

Rose bengal is superior to riboflavin PDAT against selected Nocardia isolates. In vivo testing is warranted to investigate the utility of rose bengal PDAT for severe Nocardia keratitis.

Translational Relevance:

In vitro results for three clinical strains of Nocardia support the possible use of rose bengal PDAT as a complementary treatment of Nocardia keratitis.

• Authors: Ethan Adre, Heather Durkee, Alejandro Arboleda, Karam Alawa, Jorge Maestre, Keenan J Mintz, Roger M Leblanc, Guillermo Amescua, Jean-Marie Parel, Darlene Miller
• Journal: Translational vision science & technology (Transl Vis Sci Technol) Vol. 11 Issue 1 Pg. 29 (01 03 2022) ISSN: 2164-2591 [Electronic] United States
• PMID: 35044443 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Anti-Infective Agents
• Rose Bengal
• Riboflavin

Topics

• Animals
• Anti-Infective Agents
• Florida
• Humans
• Keratitis (drug therapy)
• Nocardia
• Riboflavin (pharmacology, therapeutic use)
• Rose Bengal (pharmacology)
• Sheep