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.

Photodynamic Therapy: Current Status and Future Directions

“…It was clinically approved more than a quarter of a century ago for the treatment of a small number of selected tumors [1] and has expanded tremendously to include areas of application as diverse as cardiology [2,3], urology [4], immunology [5], ophthalmology [6,7], dentistry [8,9], dermatology [10,11] and cosmetics [12,13]. Antimicrobial/antiviral PDT has been successfully used for the treatment of viral infections [14,15], against antibiotic-resistant bacterial [16,17] and fungal strains [18,19,20], for the inactivation of pathogens in blood products [21], for water sterilization [22,23] and for disinfection and sanitation of surfaces [24,25]. The photodynamic process is successfully used for drug delivery and the release of endocytosed macromolecules in the cytosol [26,27].…”

Antimicrobial, Antimycobacterial and Antibiofi lm Properties of Couroupita guianensis Aubl. Fruit Extract

“…B. atrophaeus growth was reduced by more than 4 log 10 by 10 M TMPyP and a single light �ash of 10 or 20 J/cm 2 . For all of the studied strains, higher applied radiant exposures (up to 80 J/cm 2 ) did not further increase the reduction in growth, and the authors suggested that increasing the radiant exposure appeared to produce a plateau in the killing efficacy [58]. To inactivate P. chrysogenum conidia, Gomes et al studied porphyrin derivatives based on 5-,10-,15-,20-tetrakis(4-pyridyl) porphyrin and 5-, 10-,15-,20-tetrakis(penta�uorophenyl) porphyrin [59].…”

“…In S. mutans, Rolim et al did not observe photodynamic activity when MB was used at a concentration of 163.5 M at 24 J/cm 2 (LED, 640 nm), but a signi�cant reduction (3 log 10 cfu/mL) was observed when the same concentration of TBO and an equal light dose were used [57]. Maisch et al reported that incubation of methicillin-sensitive S. aureus (MSSA), methicillin-resistant S. aureus (MRSA), E. coli, and B. atrophaeus with a porphyrin derivative (TMPyP) caused a biologically relevant decrease in CFU/mL upon illumination with multiple light �ashes [58]. For MSSA, a TMPyP concentration of 1 M exhibited a killing efficacy of 2 log 10 units reduction (at a radiant exposure of 80 J/cm 2 ), and higher concentrations of TMPyP (10 or 100 M) caused a further decrease in bacterial survival (more than 5 log 10 units).…”

Strategies to optimize photosensitizers for photodynamic inactivation of bacteria

“…In addition aPDI is a very fast and effective approach to inactivate multi-resistant bacteria. In vitro studies have shown that successful inactivation up to 6-log 10 CFU are possible within seconds (incubation time plus illumination) [20]. Therefore it is under investigation how bacteria can develop defense strategies towards a lethal dose of aPDI which can occur within seconds.…”