title: Fast and effective: intense pulse light photodynamic inactivation of bacteria.
abstract: The goal of this study was to investigate the photodynamic toxicity of TMPyP (5, 10, 15, 20-Tetrakis (1-methylpyridinium-4-yl)-porphyrin tetra p-toluenesulfonate) in combination with short pulses (ms) of an intense pulse light source within 10 s against Bacillus atrophaeus, Staphylococcus aureus, Methicillin-resistant S. aureus and Escherichia coli, major pathogens in food industry and in health care, respectively. Bacteria were incubated with a photoactive dye (TMPyP) that is subsequently irradiated with visible light flashes of 100 ms to induce oxidative damage immediately by generation of reactive oxygen species like singlet oxygen. A photodynamic killing efficacy of up to 6 log(10) (>99.9999%) was achieved within a total treatment time of 10 s using a concentration range of 1-100 μmol TMPyP and multiple light flashes of 100 ms (from 20 J cm(-2) up to 80 J cm(-2)). Both incubation of bacteria with TMPyP alone or application of light flashes only did not have any negative effect on bacteria survival. Here we could demonstrate for the first time that the combination of TMPyP as the respective photosensitizer and a light flash of 100 ms of an intense pulsed light source is enough to generate sufficient amounts of reactive oxygen species to kill these pathogens within a few seconds. Increasing antibiotic resistance requires fast and efficient new approaches to kill bacteria, therefore the photodynamic process seems to be a promising tool for disinfection of horizontal surfaces in industry and clinical purposes where savings in time is a critical point to achieve efficient inactivation of microorganisms.
authors.affiliation: Department of Dermatology, Regensburg University Hospital, Franz-Josef-Strauss-Allee 11, 93053, Regensburg, Germany. tim.maisch@klinik.uni-regensburg.de
authors.forename: Tim
authors.initials: T
authors.lastname: Maisch
authors.forename: Franz
authors.initials: F
authors.lastname: Spannberger
authors.forename: Johannes
authors.initials: J
authors.lastname: Regensburger
authors.forename: Ariane
authors.initials: A
authors.lastname: Felgenträger
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Bäumler
mesh_terms: D004203:Disinfection / Q000295:instrumentation / Q000379:methods*; D004783:Environmental Microbiology; D004926:Escherichia coli / Q000187:drug effects / Q000528:radiation effects*; D008027:Light; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects / Q000528:radiation effects*; D017319:Photosensitizing Agents / Q000494:pharmacology*; D011166:Porphyrins / Q000494:pharmacology*; D026082:Singlet Oxygen / Q000737:chemistry; D013211:Staphylococcus aureus / Q000187:drug effects / Q000528:radiation effects*; D013997:Time Factors
chemical_list: D017319:Photosensitizing Agents; D011166:Porphyrins; D026082:Singlet Oxygen; C021096:tetra(4-N-methylpyridyl)porphine