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We report the results of experimental studies on the effect of ultraviolet (UV) radiation in a wide spectral range of 270–405 nm on bovine coronavirus. The sensitivity of bovine coronavirus to UV radiation is determined, a comparative analysis of the data is performed, and action spectra are constructed. It is shown that bovine coronavirus inactivation is possible in the UV-A range, which will make it possible to select safe radiation sources for use in public places in the presence of people. [ABSTRACT FROM AUTHOR]

Photodynamic inactivation (PDI) is a technique to inhibit microbial biofilm growth through the toxicity of Reactive Oxygen Species (ROS) compounds. ROS can be attack membrane, lipids, DNA and nucleic acid then initiate cell necrosis. This study aims to analyze the potential of red and blue LEDs to activating silver nanoparticles (AgNPs) to produce significant amounts of ROS that are believed to be toxic and lethal to Candida albicans biofilm cells. The effectiveness of the treatment in this study was evaluated through cell viability represented by Optical Density values and malondialdehyde levels. There were 4 treatment groups used as samples, namely the control group, the photosensitizer group, the light group, and the combination group of light with photosensitizer. The duration of light exposure ranged from 2 to 10 min with a power of 100 MW. The biofilm staining done to detection some indicator as an impact of photodynamic against mortality and survive cell with 2 dyes are XTT assay as cell viability values and the Thiobarbituric Acid Reactive Substances assay for malondialdehyde levels. The results showed that photoinactivation of Candida albicans biofilm with the lowest viability occurred in the treatment group of the combination of blue light with AgNPs with an irradiation duration of 10 min, namely 0.076 ± 0.005 and the treatment group of the combination of red light with AgNPs with an irradiation duration of 10 min, namely 0.131 ± 0.021. The data resulted in an inactivation rate of 94.68 ± 0.55 % for blue light and 90.98 ± 0.02 % for red light. The malondialdehyde levels were 1.563 nmol/mL for blue light and 1.514 nmol/mL for red light. The comparison of blue light treatment with red light is based on penetration in the cell, where blue light has low penetration but high energy which gives more opportunities to produce ROS at the triplet level. The combination of blue LED spectrum with AgNPs is highly effective in inactivating the metabolic activity of pathogenic microbial cells. [ABSTRACT FROM AUTHOR]

Aeromonas hydrophila can be a substantial concern, as it causes various diseases in aquaculture. An effective and green method for inhibiting A. hydrophila is urgently required. Emodin, a naturally occurring anthraquinone compound, was exploited as a photo-antimicrobial agent against A. hydrophila. At the minimum inhibitory concentration of emodin (256 mg/L) to inactivate A. hydrophilia in 30 min, an 11.32% survival rate was observed under 45 W white compact fluorescent light irradiation. In addition, the antibacterial activity under natural sunlight (0.78%) indicated its potential for practical application. Morphological observations demonstrated that the cell walls and membranes of A. hydrophila were susceptible to damage by emodin when exposed to light irradiation. More importantly, the photoinactivation of A. hydrophila was predominantly attributed to the hydroxyl radicals and superoxide radicals produced by emodin, according to the trapping experiment and electron spin resonance spectroscopy. Finally, a light-dependent reactive oxygen species punching mechanism of emodin to photoinactivate A. hydrophila was proposed. This study highlights the potential use of emodin in sunlight-mediated applications for bacterial control, thereby providing new possibilities for the use of Chinese herbal medicine in aquatic diseases prevention. [ABSTRACT FROM AUTHOR]

Palladium-catalyzed heterylation of monobromophenyl-substituted zinc(II) porphyrin with small heterocycles (benzothiazole, benzoxazole, and N-methylbenzimidazole) was carried out. As a result, unsymmetrical heterylphenyl-substituted zinc(II) porphyrins soluble in organic solvents were obtained. The interaction of heteryl-substituted zinc(II) porphyrins with alpha-helical proteins was studied by spectral methods using bovine serum albumin in aqueous organic solvents. It was found that the titration of the zinc(II) porphyrins with albumin in a sodium phosphate buffer involves a number of equilibria including complexation and aggregation. In the case of porphyrins containing N-methylbenzimidazole and benzoxazole residues, self-aggregation processes initiated by absorption of organic solvent molecules by the protein predominate. It was found that more hydrophobic nature of zinc(II) porphyrin with benzothiazole residue promotes the complex formation with the protein. The photochemical properties of zinc(II) porphyrin with a benzothiazole residue, capacity for the photooxidation of the alpha-helical protein, and the high affinity of protein to this porphyrin make it a promising candidate for the potential applicability for photodynamic inactivation. [ABSTRACT FROM AUTHOR]

Impedance spectroscopy was employed to assess the electrical properties of yeast following 405 nm laser irradiation, exploring the effects of visible, non-ionizing laser-induced inactivation as a more selective and safer alternative for photoinactivation applications compared to the use of DNA targeting, ionizing UV light. Capacitance and impedance spectra were obtained for yeast suspensions irradiated for 10, 20, 30, and 40 min using 100 and 200 mW laser powers. Noticeable differences in capacitance spectra were observed at lower frequencies (40 Hz to 1 kHz), with a significant increase at 40 min for both laser powers. β-dispersion was evident in the impedance spectra in the frequency range of 10 kHz to 10 MHz. The characteristic frequency of dielectric relaxation steadily shifted to higher frequencies with increasing irradiation time, with a drastic change observed at 40 min for both laser powers. These changes signify a distinct alteration in the physical state of yeast. A yeast spot assay demonstrated a decrease in cell viability with increasing laser irradiation dose. The results indicate a correlation between changes in electrical properties, cell viability, and the efficacy of 405 nm laser-induced inactivation. Impedance spectroscopy is shown to be an efficient, non-destructive, label-free method for monitoring changes in cell viability in photobiological effect studies. The development of impedance spectroscopy-based real-time studies in photoinactivation holds promise for advancing our understanding of light-cell interactions in medical applications. [ABSTRACT FROM AUTHOR]

Background: The World Health Organization has published a list of pathogenic fungi with prioritizing groups and calls for research and development of antifungal measures, with Candida auris belonging to the group with high priority. Methods: The photosensitivity towards short wavelength ultraviolet irradiation (Far-UVC, UVC, and UVB) was investigated and compared to other yeasts (Saccharomyces cerevisiae) and a mold (Cladosporium cladosporioides). The observed 1-log reduction doses were compared to literature values of other representatives of the genus Candida, but also with S. cerevisiae, Aspergillus niger, and A. fumigatus. Results: For the determined 1-log reduction doses, an increase with higher wavelengths was observed. A 1-log reduction dose of 4.3 mJ/cm2 was determined for C. auris when irradiated at 222 nm, a dose of 6.1 mJ/cm2 at 254 nm and a 1-log reduction dose of 51.3 mJ/cm2 was required when irradiated with UVB. Conclusions: It was observed that S. cerevisiae is a possible surrogate for C. auris for irradiation with Far-UVC and UVB due to close 1-log reduction doses. No surrogate suitability was verified for C. cladosporioides in relation to A. niger and A. fumigatus for irradiation with a wavelength of 254 nm and for A. niger at 222 nm.

The development of sustainable alternatives to chemical and mechanical biofilm removal for submerged technical devices used in freshwater and marine environments represents a major technical challenge. In this context, the antibiotic impact of blue light with its low absorption underwater provides a potentially useful alternative. However, former technical limitations led to hours of treatment. Here, we applied high-power blue laser irradiation (1500 W) with a wavelength of 448 nm to demonstrate its strong antibiotic and algicidal effect on different bacteria and algae in seconds. High-power blue light treatment (139 W/cm2) for only 8.9 s led to the efficient deactivation of all tested organisms. Analyses of the underlying biological mechanisms revealed the absorption of the blue light by endogenous chromophores (flavins, tetrapyrroles) with the generation of reactive oxygen species (ROS). In agreement, Escherichia coli transcriptome analyses demonstrated a stress response at the level of DNA damage repair, respiration, and protein biosynthesis. Spectroscopic measurements of the irradiated algae indicated the irreversible damage of chlorophyll by photooxidation with the formation of singlet oxygen. In conclusion, high-power blue laser radiation provides a strong sustainable tool for the removal of biofouling in a very short time for applications in aquatic systems. [ABSTRACT FROM AUTHOR]

Ventilator-associated pneumoniae (VAP) are a major problem in intensive care units. Previous in vitro experiments revealed that blue or violet luminescent endotracheal tubes are capable of inhibiting bacterial growth and may thus prevent pathogens from entering the lung. However, while these in vitro studies were conducted in a relatively transparent bacterial suspension, subglottic secretions around endotracheal tubes can also contain highly absorbent components, such as blood. To investigate if light has an antimicrobial effect under such conditions, staphylococcal solutions containing various absorbent components were irradiated by blue or violet luminescent endotracheal tubes for up to 24 h in a tracheal model. Light was generated externally by LEDs or lasers and entered the tube via light guides. An antimicrobial effect was observed for blue and violet light, which was, however, inhibited to some extent in the presence of light adsorbing molecules. Under these conditions, violet light had a stronger effect than blue at low absorptions, while at strong absorptions the effects converged, with blue light even exhibiting a slightly stronger impact. Significant differences between lasers and LEDs could not be detected. In our model, inhibition of bacterial growth could be observed even in the presence of light absorbing molecules. Illuminating endotracheal tubes with blue or violet light may thus represent a promising strategy to migration of bacteria from the oropharynx into the trachea and, thereby, possibly decrease the incidence of VAP.

In this study, the fabrication of titanium dioxide/reduced graphene oxide (TiO2/rGO) utilising banana peel extracts (Musa paradisiaca L.) as a reducing agent for the photoinactivation of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was explored. The GO synthesis was conducted using a modified Tour method, whereas the production of rGO involved banana peel extracts through a reflux method. The integration of TiO2 into rGO was achieved via a hydrothermal process. The successful synthesis of TiO2/rGO was verified through various analytical techniques, including X-ray diffraction (XRD), gas sorption analysis (GSA), Fourier-transform infrared (FT-IR) spectroscopy, ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS), scanning electron microscope-energy dispersive X-ray (SEM-EDX) and transmission electron microscopy (TEM) analyses. The results indicated that the hydrothermal-assisted green synthesis effectively produced TiO2/rGO with a particle size of 60.5 nm. Compared with pure TiO2, TiO2/rGO demonstrated a reduced crystallite size (88.505 nm) and an enhanced surface area (22.664 m2/g). Moreover, TiO2/rGO featured a low direct bandgap energy (3.052 eV), leading to elevated electrical conductivity and superior photoconductivity. To evaluate the biological efficacy of TiO2/rGO, photoinactivation experiments targeting E. coli and S. aureus were conducted using the disc method. Sunlight irradiation emerged as the most effective catalyst, achieving optimal inactivation results within 6 and 4 h.

Directed synthesis of a new cationic monoheteryl-substituted porphyrin, 5-[4′-(1′′,3′′,7′′-trimethyixanth-2′′-yl]-10,15,20-tris-(N-methylpyridinium-3′-yl) porphyrin triiodide was carried out. This porphyrin is in a partially associated state in Tris-buffer solutions at pH = 7.4, and has a long fluorescence lifetime (~9 ns). It has been found that the synthetic nucleic acid binds the synthesized porphyrin in the groove with an affinity constant of 2.3×107. It has been shown that the porphyrin binding by poly[d(AT)2] leads to a decrease in the particle size. Photoirradiation of the porphyrin complex with poly[d(AT)2] by visible light leads to the destruction of the nucleic acid and enhances the porphyrin photolysis. [ABSTRACT FROM AUTHOR]

Directed synthesis of a new cationic monoheteryl-substituted porphyrin, 5-[4′-(1′′,3′′,7′′-trimethyixanth-2′′-yl]-10,15,20-tris-(N-methylpyridinium-3′-yl) porphyrin triiodide was carried out. This porphyrin is in a partially associated state in Tris-buffer solutions at pH = 7.4, and has a long fluorescence lifetime (~9 ns). It has been found that the synthetic nucleic acid binds the synthesized porphyrin in the groove with an affinity constant of 2.3×107. It has been shown that the porphyrin binding by poly[d(AT)2] leads to a decrease in the particle size. Photoirradiation of the porphyrin complex with poly[d(AT)2] by visible light leads to the destruction of the nucleic acid and enhances the porphyrin photolysis. [ABSTRACT FROM AUTHOR]

Diatoms form a major component of phytoplankton. These eukaryotic organisms are responsible for approximately 40% of primary productivity in the oceans and contribute significantly to the food web. Here, the influences of ultraviolet radiation (UVR) and ocean warming on diatom photosynthesis were investigated in Thalassiosira pseudonana. The organism was grown at two temperatures, namely, 18°C, the present surface water temperature in summer, and 24°C, an estimate of surface temperature in the year 2,100, under conditions of high photosynthetically active radiation (P, 400–700 nm) alone or in combination with UVR (P + UVR, 295–700 nm). It was found that the maximum photochemical yield of PSII (Fv/Fm) in T. pseudonana was significantly decreased by the radiation exposure with UVR at low temperature, while the rise of temperature alleviated the inhibition induced by UVR. The analysis of PSII subunits turnover showed that high temperature alone or worked synergistically with UVR provoking fast removal of PsbA protein (KPsbA), and also could maintain high PsbD pool in T. pseudonana cells. With the facilitation of PSII repair process, less non-photochemical quenching (NPQ) occurred at high temperature when cells were exposed to P or P + UVR. In addition, irrespective of radiation treatments, high temperature stimulated the induction of SOD activity, which partly contributed to the higher PSII repair rate constant (Krec) as compared to KPsbA. Our findings suggest that the rise in temperature could benefit the photosynthetic performance of T. pseudonana via modulation of its PSII repair cycle and protective capacity, affecting its abundance in phytoplankton in the future warming ocean. [ABSTRACT FROM AUTHOR]

The interaction of cobalt(II) tetrasulfophthalocyanine (CoPc) with the ORF8 accessory protein of SARS-CoV-2 was studied by spectroscopy and calorimetry. The protein was found to shift the aggregation equilibrium in cobalt tetrasulfophthalocyanine solutions towards dimerization. Most probably, the CoPc dimer binds to ORF8 on the greater β-sheet side, thus causing fluorescence quenching. The protein affinity constant to CoPc dimer is 1.5 × 105. Differential scanning calorimetry data indicate that ORF8 undergoes thermally induced denaturation in the temperature range of 38–67°C. Melting of ORF8 includes two stages, which partly overlap. The complex formation of ORF8 with CoPc leads to thermal stabilization of the protein, thus preventing the second stage of protein unfolding. Denaturation of the complex proceeds between 40 and 77°C as two temperature-separated stages. According to gel electrophoresis and immunoblotting data, visible light photoirradiation of the ORF8 complex with CoPc does not induce photooxidation of the protein. It was shown that water-soluble cobalt sulfo-substituted phthalocyanine can be considered as a potential drug inhibiting the ORF8 accessory protein. [ABSTRACT FROM AUTHOR]

In this study, the efficacy of using Sauropus androgynus (L) Merr, a katuk leaf chlorophyll photosensitizer, to reduce Aggregatibacter actinomycetemcomitans and Enterococcus faecalis biofilm was investigated. A red and blue diode laser is used as the light source. The sample was split into four groups: a negative control group, a positive control group, a blue laser treatment group (B), and a red laser treatment group (R), both with and without the addition of katuk leaf chlorophyll 1.6 mg/ml, and with varying densities of laser energy exposure of 2.5 J/cm2, 5 J/cm2, 7.5 J/cm2, and 10 J/cm2. Laser exposure and chlorophyll photosensitizer were tested using ELISA and ANOVA. At an energy density of 10 J/cm2, the optimal bacterial mortality rate was obtained in each treatment group. Namely, in the Aggregatibacter actinomycetemcomitans biofilm, the negative group, the number of deaths was 73.30% using a blue diode laser and 63.25% using a red diode laser. In the positive group, the number of deaths was 86.12% using a blue diode laser and 83.29% using a red diode laser. In the Enterococcus faecalis biofilm, in the negative group, the number of deaths was 67.78% using the blue diode laser and 75.33% using the red diode laser, and in the positive group, the number of deaths was 71.71% using the blue diode laser and 86.41 using a red diode laser. Exposure to blue and red diode lasers activates chlorophyll in katuk leaves, killing bacteria and reducing biofilms.

Several types of phototherapy target human pathogens and Porphyromonas gingivitis (Pg) in particular. The various approaches can be organized into five different treatment modes sorted by different power densities, interaction times, effective wavelengths and mechanisms of action. Mode 1: antimicrobial ultraviolet (aUV); mode 2: antimicrobial blue light (aBL); mode 3: antimicrobial selective photothermolysis (aSP); mode 4: antimicrobial vaporization; mode 5: antimicrobial photodynamic therapy (aPDT). This report reviews the literature to identify for each mode (a) the putative molecular mechanism of action; (b) the effective wavelength range and penetration depth; (c) selectivity; (d) in vitro outcomes; and (e) clinical trial/study outcomes as these elements apply to Porphyromonas gingivalis (Pg). The characteristics of each mode influence how each is translated into the clinic. [ABSTRACT FROM AUTHOR]

Background: Aspergillus niger is one of the most common fungal contaminants of food products, leading to several economic losses on fruit, vegetables and other food products during storage. Over the years, several new techniques have been developed to control fungal growth, including photodynamic inactivation, in which excitation of a photosensitizer in the right wavelength leads to ROS production and microbial death. Results: On this paper, curcumin was used as a natural photosentitizer against A. niger spores. Nanoemulsions were used in order to encapsulated curcumin and increase its water solubility. Results showed that spores inhibition could reach up to 80% after 3 min of irradiation while values for un‐encapsulated curcumin were around 30%. Conclusion: Results presented show that nanoemulsions could be use to enhance the photoinactivation properties of curcumin, against fungal spores from A. niger. This type of process can be use for food decontamination and preservation. [ABSTRACT FROM AUTHOR]

Today, the search for safe ways to inactivate pathogens is becoming especially relevant in connection with the corona- virus pandemic. Standard methods using chlorides and ultraviolet irradiation have disadvantages related to toxicity and low efficiency. Photodynamic inactivation involving nanoparticles is already used to disinfect water and air from microorganisms and enveloped viruses such as human herpes simplex virus, vesicular stomatitis virus, human immuno- deficiency virus, and hepatitis B and C viruses. The aim of this work was to evaluate the possibility of the inactivation of human adenovirus type 5 in an organic medium using titanium dioxide irradiated with ultraviolet light. Methods. The nanosized titanium dioxide material was obtained by the thermal decomposition of a suspension of hydrated titanium dioxide TiO(OH)2, (metatitanic acid). The analysis of the morphology of the TiO2, nanopowder was carried out using electron scanning microscopy (SEM), which showed that TiO2, nanopowder contains soft aggregates of nanoparticles mostly 20-30 nm in size. Cytotoxicity, virulicidal and antiviral action of titanium dioxide were determined by standard methods using (3-(4,5-dimathylthiazol-2-yl)-2,5-dipheniltetrazolium bromide (MTT). The titanium dioxide suspension was irradiated at a distance of 20 cm from 1 to 30 min with a bactericidal UV lamp (OBB15P, BactoSfera, Poland (254 nm). The concentration of nanoparticles for irradiation was 1.0 mg/mL. Adenovirus suspension with titer 6.0 log10, TCID50/mL was added to the nanoparticles immediately after irradiation. The titer of virus synthesized in the presence of titanium dioxide was determined by the end of the virus dilution, which causes 50% of the cytopathic effect of the virus on cells. All studies were performed in three replicates; the number of parallel determinations was three. Results. A dose-dependent effect of titanium dioxide nanoparticles on the viability of Hep-2 cells was revealed. At the NPs concen- tration of 1 mg/mL, quite a low cell viability was observed (32—39%), with a decrease in concentration to 0.1 and 0.01 mg/mL, the NPs were less toxic (cell viability was in the range of 62—90%). The TiO2, NPs dissolved in glycerin-water had no virulicidal effect, as the virus titer was similar to the control values. Instead, NPs dissolved in propanediol- ethanol reduced the infectious titer of the virus by 6.0 log10, which indicates their high virulicidal effect. The absence of an antiviral effect was shown when NPs were added to infected cells. A decrease in the virus titer by 4.5-5.0 log10 was recorded uponitsinteracting with irradiated NPs for 1-30 min. The effect persisted for 3 h after exposure to NPs. Conclu- sions. The cytotoxic, virulicidal, and antiviral effects of optically active TiO2, nanoparticles were determined in optimal conditions. Regardless of the solvent, NPs had low toxicity at a concentration of 0.1 mg/mL. The TiO2, NPs dissolved in glycerin-water had no virulicidal effect; but dissolved in propanediol-ethanol reduced the infectious titer of the virus by 6.0 log10, which indicates its high virulicidal effect. NPs in a propanediol-ethanol solution, irradiated with UV for 1-30 min, completely inhibited adenovirus reproduction. NPs in a glycine-water solution reduced the virus titer by 0.5 log10. The control with NPs without irradiation slightly reduced the virus titer (by 0.45 log10). The ability of NPs to completely inactivate adenovirus was maintained for 3 h. It was shown for the first time that the non-enveloped HAdV5 virus could be efficiently inactivated by UV-induced TiO2, photocatalysis. [ABSTRACT FROM AUTHOR]

Visible blue light emitting diodes (LED) have been studied to inactivate Escherichia coli (E. coli) O157:H7 in agar gels. The LED array was optimized to attain uniform light illumination, and the light intensity distribution was visualized through optical simulation. The uniformity of LED light intensity was assessed, and the evenly spaced array showed the best uniformity with a Petri factor of 0.99. Microbial populations in agar gels prepared with and without a dye were analyzed after light irradiation. Each segment of the gels with different heights was taken to measure microbial reduction, and the results indicated that optical properties, such as opaqueness, played an important role in microbial reduction. The agar gel without and with a dye showed a maximum reduction of <3.4 and <2.1 log CFU/g, respectively. An exposure assessment for E. coli O157:H7 was conducted based on the assumption for the agar gel product after LED illumination. The probability results indicated that a risk (>5 log CFU/g) existed mainly in the bottom layer of the sample, despite the average contamination being <5 log CFU/g. This study provides a suitable approach for designing the LED photoinactivation process and subsequent exposure assessment to avoid risk. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to evaluate the efficiency of infrared LEDs with a magnetic solenoid field in lowering the quantity of gram-positive Staphylococcus aureus and gram-negative Escherichia coli bacteria, as well as the best exposure period and energy dose for inactivating these bacteria. Method: Research has been performed on a photodynamic therapy technique called photodynamic inactivation (PDI), which combines infrared LED light with a wavelength range of 951–952 nm and a solenoid magnetic field with a strength of 0–6 mT. The two, taken together, can potentially harm the target structure biologically. Infrared LED light and an AC-generated solenoid magnetic field are both applied to bacteria to measure the reduction in viability. Three different treatments infrared LED, solenoid magnetic field, and an amalgam of infrared LED and solenoid magnetic field, were used in this study. A factorial statistical ANOVA analysis was utilized in this investigation. Results: The maximum bacterial production was produced by irradiating a surface for 60 min at a dosage of 0.593 J/cm2, according to the data. The combined use of infrared LEDs and a magnetic field solenoid resulted in the highest percentage of fatalities for Staphylococcus aureus, which was 94.43 s. The highest percentage of inactivation for Escherichia coli occurred in the combination treatment of infrared LEDs and a magnetic field solenoid, namely, 72.47 ± 5.06%. In contrast, S. aureus occurred in the combined treatment of infrared LEDs and a magnetic field solenoid, 94.43 ± 6.63 percent. Conclusion: Staphylococcus aureus and Escherichia coli germs are inactivated using infrared illumination and the best solenoid magnetic fields. This is evidenced by the rise in the proportion of bacteria that died in treatment group III, which used a magnetic solenoid field and infrared LEDs to deliver a dosage of 0.593 J/cm2 over 60 min. According to the research findings, the magnetic field of the solenoid and the infrared LED field significantly impact the gram-positive bacteria S. aureus and the gram-negative bacteria E. coli. [ABSTRACT FROM AUTHOR]

Background: Streptococcus agalactiae, referred to as Group B Streptococcus (GBS), is a prominent bacterium causing life-threatening neonatal infections. Although antibiotics are efficient against GBS, growing antibiotic resistance forces the search for alternative treatments and/or prevention approaches. Antimicrobial photodynamic inactivation (aPDI) appears to be a potent alternative non-antibiotic strategy against GBS. Methods: The effect of rose bengal aPDI on various GBS serotypes, Lactobacillus species, human eukaryotic cell lines and microbial vaginal flora composition was evaluated. Results: RB-mediated aPDI was evidenced to exert high bactericidal efficacy towards S. agalactiae in vitro (>4 log10 units of viability reduction for planktonic and >2 log10 units for multispecies biofilm culture) and in vivo (ca. 2 log10 units of viability reduction in mice vaginal GBS colonization model) in microbiological and metagenomic analyses. At the same time, RB-mediated aPDI was evidenced to be not mutagenic and safe for human vaginal cells, as well as capable of maintaining the balance and viability of vaginal microbial flora. Conclusions: aPDI can efficiently kill GBS and serve as an alternative approach against GBS vaginal colonization and/or infections. [ABSTRACT FROM AUTHOR]

The development of sustainable alternatives to chemical and mechanical biofilm removal for submerged technical devices used in freshwater and marine environments represents a major technical challenge. In this context, the antibiotic impact of blue light with its low absorption underwater provides a potentially useful alternative. However, former technical limitations led to hours of treatment. Here, we applied high-power blue laser irradiation (1500 W) with a wavelength of 448 nm to demonstrate its strong antibiotic and algicidal effect on different bacteria and algae in seconds. High-power blue light treatment (139 W/cm2) for only 8.9 s led to the efficient deactivation of all tested organisms. Analyses of the underlying biological mechanisms revealed the absorption of the blue light by endogenous chromophores (flavins, tetrapyrroles) with the generation of reactive oxygen species (ROS). In agreement, Escherichia coli transcriptome analyses demonstrated a stress response at the level of DNA damage repair, respiration, and protein biosynthesis. Spectroscopic measurements of the irradiated algae indicated the irreversible damage of chlorophyll by photooxidation with the formation of singlet oxygen. In conclusion, high-power blue laser radiation provides a strong sustainable tool for the removal of biofouling in a very short time for applications in aquatic systems.

Prior to the coronavirus disease-19 (COVID-19) pandemic, the germicidal effects of visible light (λ = 400 – 700 nm) were well known. This review provides an overview of new findings that suggest there are direct inactivating effects of visible light – particularly blue wavelengths (λ = 400 – 500 nm) – on exposed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virions, and inhibitory effects on viral replication in infected cells. These findings complement emerging evidence that there may be clinical benefits of orally administered blue light for limiting the severity of COVID-19. Possible mechanisms of action of blue light (e.g., regulation of reactive oxygen species) and important mediators (e.g., melatonin) are discussed.

In this work, two compounds belonging to the BODIPY family, and previously investigated for their photosensitizing properties, have been bound to the amino-pendant groups of three random copolymers, with different amounts of methyl methacrylate (MMA) and 2-(dimethylamino)ethyl methacrylate (DMAEMA) in the backbone. The P(MMA-ran-DMAEMA) copolymers have inherently bactericidal activity, due to the amino groups of DMAEMA and to the quaternized nitrogens bounded to BODIPY. Systems consisting of filter paper discs coated with copolymers conjugated to BODIPY were tested on two model microorganisms, Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). On solid medium, irradiation with green light induced an antimicrobial effect, visible as a clear inhibition area around the coated disks. The system based on the copolymer with 43% DMAEMA and circa 0.70 wt/wt% of BODIPY was the most efficient in both bacterial species, and a selectivity for the Gram-positive model was observed, independently of the conjugated BODIPY. A residual antimicrobial activity was also observed after dark incubation, attributed to the inherently bactericidal properties of copolymers. [ABSTRACT FROM AUTHOR]

Photodynamic antimicrobial chemotherapy (PACT) is extensively studied as a strategic method to inactivate pathogenic microbes in wastewater for addressing the limitations associated with chlorination, ozonation, and ultraviolet irradiation as disinfection methods, which generally promote the development of resistant genes and harmful by-products such as trihalomethanes. PACT is dependent on photons, oxygen, and a photosensitizer to induce cytotoxic effects on various microbes by generating reactive oxygen species. Photosensitizers such as porphyrins have demonstrated significant microbial inactivation through PACT, hence now explored for wastewater phototreatment. This review aims to evaluate the efficacy of porphyrins and porphyrin-conjugates as photosensitizers for wastewater photoinactivation. Concerns relating to the application of photosensitizers in water treatment are also evaluated. This includes recovery and reuse of the photosensitizer when immobilized on solid supports. [ABSTRACT FROM AUTHOR]

Invasive candidiasis is an important cause of morbidity and mortality, and its occurrence is increasing due to the growing complexity of patients. In particular, Candida albicans exhibits several virulence factors that facilitate yeast colonization in humans. In this sense, the photodynamic inactivation of yeasts is a promising new alternative to eliminate fungal infections. Herein, the photodynamic activity sensitized by a free-base chlorin (TPCF16) and its complexes with Zn(II) (ZnTPCF16) and Pd(II) (PdTPCF16) was investigated in order to eliminate C. albicans under different forms of cell cultures. A decrease in cell survival of more than 5 log was found in planktonic cells incubated with 5 μM TPCF16 or ZnTPCF16 upon 15 min of white-light irradiation. The mechanism of action mainly involved a type II pathway in the inactivation of C. albicans cells. In addition, the photodynamic action induced by these chlorins was able to suppress the growth of C. albicans in a culture medium. These photosensitizers were also effective to photoinactivate C. albicans pseudohyphae suspended in PBS. Furthermore, the biofilms of C. albicans that incorporated the chlorins during the proliferation stage were completely eradicated using 5 μM TPCF16 or ZnTPCF16 after 60 min of light irradiation. The studies indicated that these chlorins are effective photosensitizing agents to eliminate C. albicans as planktonic cells, pseudohyphae, and biofilms. [ABSTRACT FROM AUTHOR]

The spread of infections, as in the coronavirus pandemic, leads to the desire to perform disinfection measures even in the presence of humans. UVC radiation is known for its strong antimicrobial effect, but it is also harmful to humans. Visible light, on the other hand, does not affect humans and laboratory experiments have already demonstrated that intense visible violet and blue light has a reducing effect on bacteria and viruses. This raises the question of whether the development of pathogen-reducing illumination is feasible for everyday applications. For this purpose, a lighting device with white and violet LEDs is set up to illuminate a work surface with 2,400 lux of white light and additionally with up to 2.5 mW/cm2 of violet light (405 nm). Staphylococci are evenly distributed on the work surface and the decrease in staphylococci concentration is observed over a period of 46 hours. In fact, the staphylococci concentration decreases, but with the white illumination, a 90% reduction occurs only after 34 hours; with the additional violet illumination the necessary irradiation time is shortened to approx. 3.5 hours. Increasing the violet component probably increases the disinfection effect, but the color impression moves further away from white and the low disinfection durations of UVC radiation can nevertheless not be achieved, even with very high violet emissions.

Reproductive biotechnologies are widely consolidated as a methodology in cattle breeding and have an important impact on the genetic improvement of cattle herds. Semen is an important source of dissemination of pathogenic microorganisms during reproductive procedures. To ensure the sanitary quality of the semen, it is essential to consider the presence of various microorganisms including viruses. One of the main viral agents of reproductive interest is Bovine Alphaherpesvirus 1 (BoHV-1), the etiological agent responsible for bovine rhinotracheitis and vulvovaginitis and frequently associated with reproductive efficiency of matrices and bulls. In artificial insemination centers, semen treatment is generally based only on the use of antibiotics, ignoring the possibility of inactivating other non-bacterial infectious agents. In this context, photodisinfection emerges as a promising alternative to inactivate a wide range of microorganisms, offering a complementary or substitution approach to those conventional semen treatment methods. In this work, we evaluated the use of four halogenated sulfonated porphyrins as potential photosensitizers (PSs) for photodynamic inactivation of Bovine Alphaherpesvirus I (BoHV-1) for bovine semen disinfection. The PSs were synthesized and photophysical parameters, such as UV–Vis absorption spectra and singlet oxygen quantum yield (Φ Δ) were presented. Photoinactivation of BoHV-1 was first shown in cell culture and then confirmed in artificially infected bovine semen and then the phototoxicity of PSs against spermatozoa was evaluated. All PSs were effective in BoHV-1 inactivation; however, the photosensitizer containing two chlorine atoms, showed to be more efficient due to the shorter time required for complete viral inactivation. The slight alterations in sperm kinetics were observed, but remained within those acceptable by regulatory agencies for animal reproduction. Although the methodology used in this work only included bovine semen, we emphasize that the proposed photodisinfection methodology can be adapted and applied to a wide range of biological materials and microorganisms of animal or human interest. • Photodisinfection technique demonstrates significant potential for cleaning contaminated semen. • Halogenated sulfonated porphyrins are effective for Alfaherpesvirus 1 inactivation in both cell culture and semen. • Computer Assisted Sperm Analysis attested to the quality of the bovine semen after photodisinfection. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesis of monocationic and dicationic TzTz derivatives. • First use of thiazolothiazole derivatives as photosensitizers for antimicrobial applications. • Effective photoinactivation of S. aureus with a monocationic TzTz derivative. The assessment of thiazolothiazoles (TzTz) as photosensitizers in photodynamic inactivation (PDI) experiments is reported for the first time. Mono and dicationic TzTz derivatives were synthesized, and their photosensitizing ability was assessed on Staphylococcus aureus cells, both in suspension or attached to a surface, and using white light. The biological results showed that the photodynamic efficiency of these derivatives is dependent on the TzTz structure and irradiation time. The best results were obtained with the monocationic derivative TPATzTzPyMe+ that allowed to reach a value over 7 log (99.9999 %) cell inactivation after white light irradiation for 30 min. Furthermore, TPATzTzPyMe+ also revealed to be effective on the inactivation of S. aureus adhered to surfaces, a good indication of its potential to prevent biofilm formation. TPATzTzPyMe+ was also effective against Escherichia coli , with a reduction in cell viability of 5.7 log after irradiation for 30 min. [ABSTRACT FROM AUTHOR]

To understand growth limitations of photosynthetic microorganisms, and to investigate whether batch growth or certain photosynthesis-related parameters predict a turbidostat (continuous growth at constant biomass concentration) growth rate, five green algal species were grown in a photobioreactor in batch and turbidostat conditions and their susceptibilities to photoinhibition of photosystem II as well as several photosynthetic parameters were measured. Growth rates during batch and turbidostat modes varied independently of each other; thus, a growth rate measured in a batch cannot be used to determine the continuous growth rate. Greatly different photoinhibition susceptibilities in tested algae suggest that different amounts of energy were invested in repair. However, photoinhibition tolerance did not necessarily lead to a fast growth rate at a moderate light intensity. Nevertheless, we report an inverse relationship between photoinhibition tolerance and minimum saturating irradiance, suggesting that fast electron transfer capacity of PSII comes with the price of reduced photoinhibition tolerance.

OBJECTIVES: The study objective was evaluation of amotosalen and ultraviolet A (UVA) illumination-based inactivation of dengue virus (DENV) in blood platelets. MATERIALS AND METHODS: Whole blood was collected from healthy donors and platelet concentrates were prepared at a tertiary care hospital in Gurugram, India. Platelet units collected from five blood group matched individuals were pooled and spiked with DENV. The spiked platelet units were subjected to amotosalen treatment followed by UVA illumination, to evaluate the efficiency of this method for viral inactivation. The treated platelet units were evaluated for the presence of infectious DENV. Amotosalen levels were quantified in the treated samples using high-performance liquid chromatography. RESULTS: The presence of replicating DENV was not observed in spiked platelet units treated with amotosalen and UVA illumination, whereas untreated units contained actively replicating DENV. Amotosalen levels were found to be in the permissible range after photochemical inactivation. CONCLUSIONS: Amotosalen/UVA pathogen inactivation treatment showed efficient inactivation of DENV in platelet components. Therefore, it seems to be a promising method for mitigating the risk of dengue transmission through transfusion of potentially contaminated platelet components in dengue-endemic countries such as India.

SOlar DISinfection (SODIS) systems have been studied with the aim of maintaining pathogen removal efficiencies and low costs. Such systems are useful for quickly improving the situation of more than 700 million people worldwide that lack access to an improved water source. Currently, SODIS is mainly used with PET-bottles that are exposed to UV-A radiation for 6 h in the sun. Up-scaled continuous flow SODIS systems could instead provide a continuous source of drinking water, whereas the use of plastic tubes, easily available on local markets, ensures a low construction cost of the systems. Such tubes (PVC) were tested and the best option showed a UV-A transparency ratio of ∼50%, to be compared with ∼60% for PET-bottles. By using static batches in samples of this tube, the residence time was investigated and the results show that E. coli concentrations of 0 CFU/ml are reached within less than 4 h of exposure to solar radiation, starting from an initial concentration of 106 CFU/ml. It can be concluded that cheap, easily available plastic tubes can be used for treating contaminated water with the SODIS technique, which is promising for future investigations towards constructing continuous flow SODIS systems at low costs. HIGHLIGHTS Experimental determination of the UV transparency of plastic tubes.; Assessment of cheap plastic tubes available on local markets with SODIS.; Affordable plastic tubes for satisfactory SODIS treatment of contaminated water.; Biological inactivation of E. coli with sunlight in static batches in 4 h.;

Exposure to UV-A is limited by the near-UV hazard exposure limit and the actinic UV hazard exposure limit. While rapid disinfection is possible using UV-A light, the doses required to do so generally exceed safety limits for human exposure and thus face similar operational challenges as UV-C light. The UV-A pulse frequencies tested in our study are within the range investigated by others (0.1-1000 Hz), and our results are consistent with Mori et al. [[28]] (who tested 10 Hz at 10% duty cycle) but discordant to Li et al. [[12]] (who reported optimal microbial inactivation with 100 Hz pulsed UV-A versus continuous mode). Keywords: UV-A radiation; 365 nm LED light; photoinactivation; disinfection; native photosensitizers EN UV-A radiation 365 nm LED light photoinactivation disinfection native photosensitizers 1747 10 11/17/22 20221101 NES 221101 1. [Extracted from the article]

The multistage purposeful synthesis of 5,15-bis(4′-l-N-tyrosinylamidophenyl)-10,20-bis(N-methylpyridin-3′-yl)porphine diiodide was carried out, and the optimum synthesis conditions were determined. 5,15-Bis(4′-nitrophenyl)-10,20-bis(pyridin-3′-yl)porphine served as the starting porphyrin. The structure, individual character, and purity of the target compound were proved by electron spectroscopy, 1H NMR spectroscopy, mass spectrometry (MALDI TOF), and TLC. Specific features of the interaction of the synthesized porphyrin with S-protein of SARS-CoV-2 were studied using spectral and thermochemical methods, including conditions of photoirradiation. The photoirradiation of the synthesized porphyrin in a complex with the SARS-CoV-2 S-protein can result in the partial oxidation of amino acid residues of the protein and distort its primary and secondary structures. The photoirradiation of the S-protein complex with the porphyrin decreases its thermal resistance to melting by 15 °C compared to the free S-protein and causes porphyrin release. [ABSTRACT FROM AUTHOR]

Coronavirus disease 2019 is a serious disease that causes acute respiratory syndrome and negatively affects the central nervous system. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) crosses the blood-brain barrier due to the spike (S) protein on the surface of the viral particles. Thus, it is important to develop compounds that not only have an inhibitory effect but are also capable of completely deactivating the S protein function. This study describes the purposeful modification of porphyrins and proposes compounds, asymmetrically hetaryl-substituted porphyrins with benzothiazole, benzoxazole, and N-methylbenzimidazole residues, to deactivate the S protein functions. Molecular docking of SARS-CoV-2 proteins with hetaryl-substituted porphyrins showed that the viral S protein, nucleocapsid (N) protein, and non-structural protein 13 (nsp13) exhibited the highest binding affinity.Hetaryl-substituted porphyrins form strong complexes (13–14 kcal/mol) with the receptor-binding domain of the S protein, while the distance from the porphyrins to the receptor-binding motif (RBM) does not exceed 20 Å; therefore, RBM can be oxidized by 1O2, which is generated by porphyrin. Hetaryl-substituted porphyrins interact with the N protein in the serine/arginine-rich region, and a number of vulnerable amino acid residues are located in the photooxidation zone. This damage complicates the packaging of viral RNA into new virions. High-energy binding of hetaryl-substituted porphyrins with the N- and C-terminal domains of nsp13 was observed. This binding blocks the action of nsp13 as an enzyme of exoribonuclease and methyltransferase, thereby preventing RNA replication and processing. A procedure for the synthesis of hetaryl-substituted porphyrins was developed, new compounds were obtained, their structures were identified, and their photocatalytic properties were studied.

Artificial respiration is saving lives especially in the COVID-19 pandemic, but it also carries the risk to cause ventilator-associated pneumonia (VAP). VAP is one of the most common and severe nosocomial infections, often leading to death and adding a major economic burden to the healthcare system. To prevent a proliferation of microbial pathogens that cause VAP, an endotracheal tube (ETT) equipped with blue LEDs (LED-ETT) was developed. This blue wavelength exhibits antimicrobial properties but may also harm human tracheal cells at higher irradiances. Therefore, the aim of this study was to find the minimal required irradiance for microbial reduction of 1 log level in 24 h by applying LED-ETTs. A LED-ETT with 48 blue LEDs (450 nm) was fixed in a glass tube, which served as a trachea model. The investigation was carried out with irradiations of 4.2, 6.6 and 13.4 mW/cm² at 37 °C for 24 h. The experiments were performed with Acinetobacter kookii as a surrogate of Acinetobacter baumannii, which is classified as critical by the WHO. Samples of A. kookii suspensions were taken every 4 h during irradiation from the trachea model. Bacteria concentrations were quantified by determining colony forming units (CFU)/ml. A homogeneous irradiance of only 4.2 mW/cm² generated by the blue LEDs, at a LED forward current of 3.125 mA, is sufficient to achieve a 1 log reduction of A. kookii within 24 h. The total irradiation dose within this period was 360 J/cm2. Human cells survive this dose without cellular damage. Previous studies revealed that the pathogen A. baumannii is even more sensitive to blue light than A. kookii. Therefore, blue LED-ETTs are expected to reduce A. baumannii without harming human tracheal cells.

Mastitis caused by Staphylococcus aureus uses antibiotics as conventional treatment, a practice that has led to bacterial resistance. Therefore, the photodynamic inactivation of microorganisms (PDIM), has the advantage of inactivating pathogens without leading to the selection of resistant microorganisms. The objective of the study was to evaluate the antimicrobial activity of the photosensitizer (PS) Safranine-O (Sf), incorporated in the nanocarrier Pluronic® F127 against strains of S. aureus isolated from sheep milk. The reduction of contamination in experimentally contaminated milk and Muller Hilton Broth (MHB), the formation of microbial biofilm, and its effect as post dipping in the decrease of total mesophilic aerobic and Staphylococcal counts in milk were evaluated. Three strains of S. aureus (SO1, SO3, SO4) and a coagulase-negative Staphylococcus (CNS) strain (SO2) were identified through the nuc and coa genes and all were sensitive to PDIM. The minimum inhibitory concentration (MIC) ranged from 1.18 to 18.75 mg/mL in the different isolates. The SO4 strain was resistant to Ampicillin and Trimetropim. When the microorganisms were cultivated in milk and MHB, there was a reduction in staph counts by 97.33% and 99.63%, respectively. In stainless steel coupons, photoinactivation reduced S. aureus adhesion by up to 45.92% (milk) and 99.5% (MHB) (p

Several types of phototherapy target human pathogens and Porphyromonas gingivitis (Pg) in particular. The various approaches can be organized into five different treatment modes sorted by different power densities, interaction times, effective wavelengths and mechanisms of action. Mode 1: antimicrobial ultraviolet (aUV); mode 2: antimicrobial blue light (aBL); mode 3: antimicrobial selective photothermolysis (aSP); mode 4: antimicrobial vaporization; mode 5: antimicrobial photodynamic therapy (aPDT). This report reviews the literature to identify for each mode (a) the putative molecular mechanism of action; (b) the effective wavelength range and penetration depth; (c) selectivity; (d) in vitro outcomes; and (e) clinical trial/study outcomes as these elements apply to Porphyromonas gingivalis (Pg). The characteristics of each mode influence how each is translated into the clinic.

Increased development of resistance to antibiotics among microorganisms promotes the evaluation of alternative approaches. Within this study, we examined the efficacy of antimicrobial blue light (aBL) with routinely used antibiotics against multidrug-resistant isolates of Pseudomonas aeruginosa and Staphylococcus aureus as combined alternative treatment. In vitro results of this study confirm that both S. aureus and P. aeruginosa can be sensitized to antibiotics, such as chloramphenicol, linezolid, fusidic acid or colistin, fosfomycin and ciprofloxacin, respectively. The assessment of increased ROS production upon aBL exposure and the changes in cell envelopes permeability were also goals that were completed within the current study. Moreover, the in vivo experiment revealed that, indeed, the synergy between aBL and antibiotic (chloramphenicol) occurs, and the results in the reduced bioluminescence signal of the S. aureus Xen31 strain used to infect the animal wounds. To conclude, we are the first to present the possible mechanism explaining the observed synergies among photoinactivation with blue light and antibiotics in the term of Gram-positive and Gram-negative representatives. [ABSTRACT FROM AUTHOR]

Summary: Photosystem II (PSII), which splits water molecules at minimal excess photochemical potential, is inevitably photoinactivated during photosynthesis, resulting in compromised photosynthetic efficiency unless it is repaired. The energy cost of PSII repair is currently uncertain, despite attempts to calculate it.We experimentally determined the energy cost of repairing each photoinactivated PSII in cotton (Gossypium hirsutum) leaves, which are capable of repairing PSII in darkness.As an upper limit, 24 000 adenosine triphosphate (ATP) molecules (including any guanosine triphosphate synthesized at the expense of ATP) were required to repair one entire PSII complex. Further, over a 7‐h illumination period at 526–1953 μmol photons m−2 s−1, the ATP requirement for PSII repair was on average up to 4.6% of the ATP required for the gross carbon assimilation.Each of these two measures of ATP requirement for PSII repair is two‐ to three‐fold greater than the respective reported calculated value. Possible additional energy sinks in the PSII repair cycle are discussed. [ABSTRACT FROM AUTHOR]

To investigate the effect of reduced salinity on diatoms' capacity to cope with changing ultraviolet radiation (UVR) and photosynthetically active radiation (PAR), Skeletonema costatum was grown in a range of salinity (15, 25, and 35). The photosystem II (PSII) function was analyzed by increasing PAR and UVR to mimic a mixing event in turbulent waters. The results show that high UVR exposure significantly reduced PSII activity, especially in cells grown at low salinity. UVR, but not salinity, stimulated the 'removal' rate of PSII protein PsbA. Salinity alone, in the range of 15 to 35, did not regulate PSII acceptor region; however, the low salinity+UVR treatment decreased the energy flux for electron transport per PSII reaction center in S. costatum. It showed that low salinity exacerbated the damaging effect of UVR on PSII function in S. costatum by suppressing PsbA protein synthesis and modifying the photochemistry of PSII. Although higher catalase (CAT) activity and NPQs were induced, they were unable to prevent the combined damage effect of low salinity+UVR. Our findings indicate that reduced salinity and increased UVR potentially affect the abundance and distribution of S. costatum with the escalation of climate disturbances. [ABSTRACT FROM AUTHOR]

Background: Due to the increase in multidrug-resistant pathogens, it is important to investigate further antimicrobial options. In order not to have to work directly with pathogens, the investigation of possible surrogates is an important aspect. It is examined how suitable possible surrogate candidates for ESKAPE pathogens are for UVC applications. In addition, the inactivation sensitivities to 222 and 254 nm radiation are compared in relation. Methods: Non-pathogenic members (Enterococcus mundtii, Staphylococcus carnosus, Acinetobacter kookii, Pseudomonas fluorescens and Escherichia coli) of genera of ESKAPE strains were photoinactivated in PBS with irradiation wavelengths of 222 and 254 nm (no non-pathogenic Klebsiella was available). Log reduction doses were determined and compared to published photoinactivation results on ESKAPE pathogens. It was assumed that non-pathogenic bacteria could be designated as surrogates for one wavelength and one ESKAPE strain, if the doses were between the 25 and 75% quantiles of published log reduction dose of the corresponding pathogen. Results: For all non-pathogen relatives (except A. kookii), higher average log reduction doses were required for irradiation at 222 nm than at 254 nm. Comparison by boxplot revealed that five of eight determined log reduction doses of the possible surrogates were within the 25 and 75% quantiles of the data for ESKAPE pathogens. The measured log reduction dose for non-pathogenic E. coli was above the 75% quantile at 222 nm, and the log reduction dose for S. carnosus was below the 25% quantile at 254 nm. Conclusion: For more than half of the studied cases, the examined ESKAPE relatives in this study can be applied as surrogates for ESKAPE pathogens. Because of lack of data, no clear statement could be made for Enterococcus faecalis at 222 nm and Acinetobacter baumannii at both wavelengths. [ABSTRACT FROM AUTHOR]

BackgroundDue to the increase in multidrug-resistant pathogens, it is important to investigate further antimicrobial options. In order not to have to work directly with pathogens, the investigation of possible surrogates is an important aspect. It is examined how suitable possible surrogate candidates for ESKAPE pathogens are for UVC applications. In addition, the inactivation sensitivities to 222 and 254 nm radiation are compared in relation.MethodsNon-pathogenic members (Enterococcus mundtii, Staphylococcus carnosus, Acinetobacter kookii, Pseudomonas fluorescens and Escherichia coli) of genera of ESKAPE strains were photoinactivated in PBS with irradiation wavelengths of 222 and 254 nm (no non-pathogenic Klebsiella was available). Log reduction doses were determined and compared to published photoinactivation results on ESKAPE pathogens. It was assumed that non-pathogenic bacteria could be designated as surrogates for one wavelength and one ESKAPE strain, if the doses were between the 25 and 75% quantiles of published log reduction dose of the corresponding pathogen.ResultsFor all non-pathogen relatives (except A. kookii), higher average log reduction doses were required for irradiation at 222 nm than at 254 nm. Comparison by boxplot revealed that five of eight determined log reduction doses of the possible surrogates were within the 25 and 75% quantiles of the data for ESKAPE pathogens. The measured log reduction dose for non-pathogenic E. coli was above the 75% quantile at 222 nm, and the log reduction dose for S. carnosus was below the 25% quantile at 254 nm.ConclusionFor more than half of the studied cases, the examined ESKAPE relatives in this study can be applied as surrogates for ESKAPE pathogens. Because of lack of data, no clear statement could be made for Enterococcus faecalis at 222 nm and Acinetobacter baumannii at both wavelengths.

Abstract Objective Ultraviolet radiation is known for its antimicrobial properties but unfortunately, it could also harm humans. Currently, disinfection techniques against SARS-CoV-2 are being sought that can be applied on air and surfaces and which do not pose a relevant thread to humans. In this study, the bacteriophage phi6, which like SARS-CoV-2 is an enveloped RNA virus, is irradiated with visible blue light at a wavelength of 455 nm. Results For the first time worldwide, the antiviral properties of blue light around 455 nm can be demonstrated. With a dose of 7200 J/cm2, the concentration of this enveloped RNA virus can be successfully reduced by more than three orders of magnitude. The inactivation mechanism is still unknown, but the sensitivity ratio of phi6 towards blue and violet light hints towards an involvement of photosensitizers of the host cells. Own studies on coronaviruses cannot be executed, but the results support speculations about blue-susceptibility of coronaviruses, which might allow to employ blue light for infection prevention or even therapeutic applications.

Emerging antibiotic resistance among bacterial pathogens has forced an urgent need for alternative non-antibiotic strategies development that could combat drug resistant-associated infections. Suppression of virulence of ESKAPE pathogens' by targeting multiple virulence traits provides a promising approach. Here we propose an iron-blocking antibacterial therapy based on a cationic heme-mimetic gallium porphyrin (GaCHP), which antibacterial efficacy could be further enhanced by photodynamic inactivation. We used gallium heme mimetic porphyrin (GaCHP) excited with light to significantly reduce microbial viability and suppress both the expression and biological activity of several virulence traits of both Gram-positive and Gram-negative ESKAPE representatives, i.e., S. aureus and P. aeruginosa. Moreover, further improvement of the proposed strategy by combining it with routinely used antimicrobials to resensitize the microbes to antibiotics and provide enhanced bactericidal efficacy was investigated. The proposed strategy led to substantial inactivation of critical priority pathogens and has been evidenced to suppress the expression and biological activity of multiple virulence factors in S. aureus and P. aeruginosa. Finally, the combination of GaCHP phototreatment and antibiotics resulted in promising strategy to overcome antibiotic resistance of the studied microbes and to enhance disinfection of drug resistant pathogens. Lastly, considering high safety aspects of the proposed treatment toward host cells, i.e., lack of mutagenicity, no dark toxicity and mild phototoxicity, we describe an efficient alternative that simultaneously suppresses the functionality of multiple virulence factors in ESKAPE pathogens. [Display omitted] • Strategy to eradicate critical priority pathogens and decrease their pathogenicity. • Antibacterial/anti-virulence efficacy ascribed to aPDI-stimulated generation of ROS. • Safe for human cells (no muta- and cytotoxicity and acceptable phototoxic effect). • GaCHP-aPDI results in resensitization of MDR isolates to antimicrobials. • Robust, safe, and efficient non-antibiotic strategy against ESKAPE pathogens. [ABSTRACT FROM AUTHOR]