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Proceedings Paper

Mutants of E. coli, which lack antioxidant enzymes, are more susceptible towards type-1 mechanism of action of photoantimicrobials compared to type-2 photoantimicrobials (Conference Presentation)
Author(s): Tim Maisch; Pouriya Faraj Tabrizi; Sara Wennige

Paper Abstract

ABSTRACT The photodynamic antimicrobial process is a multi-target method to inactivate pathogenic microorganisms by exciting a photoantimicrobial agent with visible light of appropriate wavelength in the presence of molecular oxygen (3O2). There are two major pathways by which reactive oxygen species (ROS) are produced. In type-1 reactions, radicals such as superoxide (O2•−) and hydroxyl radicals (•OH) are generated by electron transfer. In type-2 reactions, highly reactive singlet oxygen (1O2) is produced by direct energy transfer. This study investigated the efficiency of the photodynamic antimicrobial process in Escherichia coli wild type (EC WT) and the mutant Escherichia coli PN134 (EC PN134) which is not able to produce SOD A and SOD B, by means of two different photoantimicrobials from different chemical classes with different 1O2 quantum yields: methylene blue (MB) and 5,10,15,20-tetrakis(1-methyl-4-pyridinio)porphyrin tetra(p-toluenesulfonate) (TMPyP). Mutants, which lack antioxidant enzymes, were particularly susceptible towards type-1 reactions. When using light-activated MB, quenching agents such as superoxide dismutase (SOD) and catalase (CAT) were sufficient for protecting both the wild type and the mutant, whereas they were not able to prevent bacterial killing sufficiently using light-activated TMPyP. Summary The susceptibility of EC PN134 and EC WT differed towards photodynamic inactivation via the type-1 mechanism of action. Thus, already existing defense mechanisms against ROS in bacteria might influence the susceptibility against type-1 photodynamic mechanism of action, while this was not the case using type-2 photoantimicrobials.

Paper Details

Date Published: 14 August 2019
Proc. SPIE 11070, 17th International Photodynamic Association World Congress, 1107047 (14 August 2019); doi: 10.1117/12.2525799
Show Author Affiliations
Tim Maisch, Universitätsklinikum Regensburg (Germany)
Pouriya Faraj Tabrizi, Universitätsklinikum Regensburg (Germany)
Sara Wennige, Universitätsklinikum Regensburg (Germany)

Published in SPIE Proceedings Vol. 11070:
17th International Photodynamic Association World Congress
Tayyaba Hasan, Editor(s)

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