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Antimicrob Agents Chemother. 2017 Jun 27;61(7). pii: e00467-17. doi: 10.1128/AAC.00467-17. Print 2017 Jul.

Potassium Iodide Potentiates Antimicrobial Photodynamic Inactivation Mediated by Rose Bengal in In Vitro and In Vivo Studies.

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Department of Dermatology, West China Hospital of Sichuan University, Chengdu, Sichuan, China.
Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, Massachusetts, USA.
Department of Dermatology, Harvard Medical School, Boston, Massachusetts, USA.
Department of Cardiology, Shanghai Tenth Hospital of Tongji University, Shanghai, China.
Tongji University Cancer Institute, Tongji University School of Medicine, Shanghai, China.
Department of Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Krakow, Poland.
National Institute of Laser Enhanced Science (NILES), Cairo University, Cairo, Egypt.
Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, Massachusetts, USA
Harvard-MIT Division of Health Sciences and Technology, Cambridge, Massachusetts, USA.


Rose bengal (RB) is a halogenated xanthene dye that has been used to mediate antimicrobial photodynamic inactivation for several years. While RB is highly active against Gram-positive bacteria, it is largely inactive in killing Gram-negative bacteria. We have discovered that addition of the nontoxic salt potassium iodide (100 mM) potentiates green light (540-nm)-mediated killing by up to 6 extra logs with the Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa, the Gram-positive bacterium methicillin-resistant Staphylococcus aureus, and the fungal yeast Candida albicans The mechanism is proposed to be singlet oxygen addition to iodide anion to form peroxyiodide, which decomposes into radicals and, finally, forms hydrogen peroxide and molecular iodine. The effects of these different bactericidal species can be teased apart by comparing the levels of killing achieved in three different scenarios: (i) cells, RB, and KI are mixed together and then illuminated with green light; (ii) cells and RB are centrifuged, and then KI is added and the mixture is illuminated with green light; and (iii) RB and KI are illuminated with green light, and then cells are added after illumination with the light. We also showed that KI could potentiate RB photodynamic therapy in a mouse model of skin abrasions infected with bioluminescent P. aeruginosa.


Pseudomonas aeruginosa mouse infection; antimicrobial photodynamic inactivation; potassium iodide; reactive iodine species; rose bengal; singlet oxygen

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