Photodynamic inactivation of methicillin-resistant Staphylococcus aureus and Escherichia coli: A metalloporphyrin comparison

• Published in: Journal of photochemistry and photobiology. B, Biology Vol. 165; pp. 51 - 57
• Main Authors: Skwor, Troy A., Klemm, Stephanie, Zhang, Hanyu, Schardt, Brianna, Blaszczyk, Stephanie, Bork, Matthew A.
• Format: Journal Article
• Language: English
• Published: Switzerland Elsevier B.V 01.12.2016; Elsevier BV
• Subjects: Anti-Bacterial Agents - pharmacology; Antibiotic resistance; Antibiotics; Antiinfectives and antibacterials; Bacteria; Bactericidal activity; Chelation; Deactivation; Drug resistance; E coli; Electronic properties; Escherichia coli - drug effects; Illumination; Inactivation; Irradiation; Light emitting diodes; Light sources; Metalloporphyrin; Metalloporphyrins - pharmacology; Methicillin; Methicillin-Resistant Staphylococcus aureus - drug effects; Microorganisms; MRSA; Multidrug resistance; Oxygen; Oxygen production; Palladium; PDI; Photochemotherapy; Photosensitizing Agents - pharmacology; Porphyrins; Radiation; Reactive oxygen species; Singlet oxygen; Studies; TMPyP; Viability; T4; PDT; Singlet oxygen; PDI; ANOVA; MRSA; Metalloporphyrin; TMPyP; E. coli
• ISSN: 1011-1344; 1873-2682
• DOI: 10.1016/j.jphotobiol.2016.10.016

Increasing rates of antibiotic resistance coupled with the lack of novel antibiotics threatens proper clinical treatment and jeopardizes their use in prevention. A photodynamic approach appears to be an innovative treatment option, even for multi-drug resistant strains of bacteria. Three components are utilized in photodynamic inactivation: a photosensitizer, light source, and oxygen. Variations in photosensitizers strongly influence microbial binding and bactericidal activity. In this study, four different cationic metalloporphyrins (Cu2+, Fe2+, Pd2+, Zn2+) were compared to the free-base ligand 5,10,15,20-tetrakis(N-methylpyridinium-4-yl)porphyrin regarding their electronic properties and generation of reactive oxygen species upon subsequent 405nm violet-blue irradiation. Staphylococcus aureus and Escherichia coli were used as representatives of Gram-positive and -negative, respectively, to assess bactericidal effects by the photodynamic process. Bacterial cultures were pre-incubated with porphyrins and exposed to varying doses of 405nm irradiation (0–30J/cm2). Metalloporphyrins containing Cu2+ and Fe2+ demonstrated minimal effects on viability. Pronounced bactericidal activity was evident with free-base ligand, Zn2+, and Pd2+; though significantly stronger effects were apparent with Pd2+. Photodynamic killing was directly proportional to reactive oxygen species production post-illumination. These data provide new insight into the influence of metal chelation on photosensitizer activity on bactericidal singlet oxygen production. The strong anti-microbial photodynamic action through the use of a portable light-emitting diode over short time intervals (seconds) provides support for its potential use in self-treatment. •Chelation of palladium with photosensitizer had optimal bactericidal activity.•Gram-positive MRSA was more susceptible to PDI compared to Gram-negative E. coli.•Reduced glutathione abrogates PDI activity associated with metalloporphyrins.•Utilizing handheld LEDs for PDI supports its use for self-treatment.