Photodynamic inactivation of foodborne bacteria by eosin Y

Pseudomonas aeruginosa and related antibiotic resistance genes as indicators for wastewater treatment

This review aims to examine the existence of Pseudomonas aeruginosa (P. aeruginosa) and their antibiotic resistance genes (ARGs) in aquatic settings and the alternative treatment ways. P. aeruginosa in a various aquatic environment have been identified as contaminants with impacts on human health and the environment. P. aeruginosa resistance to multiple antibiotics, such as sulfamethoxazole, ciprofloxacin, quinolone, trimethoprim, tetracycline, vancomycin, as well as specific antibiotic resistance genes including sul1, qnrs, blaVIM, blaTEM, blaCTX, blaAIM-1, tetA, ampC, blaVIM. The development of resistance can occur naturally, through mutations, or via horizontal gene transfer facilitated by sterilizing agents. In addition, an overview of the current knowledge on inactivation of Pseudomonas aeruginosa and ARG and the mechanisms of action of various disinfection processes in water and wastewater (UV chlorine processes, catalytic oxidation, Fenton reaction, and ozonation) is given. An overview of the effects of nanotechnology and the resulting wetlands is also given.

Porphyrin-based covalent organic polymers with customizable photoresponses for photodynamic inactivation of bacteria

Porphyrin-linked covalent organic polymers (COPs) provide a reliable photocatalytic platform, while photodynamic inactivation (PDI) induced by reliable porphyrin-based COPs is considered to be an effective method to resist microbial contamination. Herein, three tunable porphyrin-based covalent organic polymers (H2-Por-COPs, OH-Por-COPs, and Zn-Por-COPs) are designed and employed for the PDI of Staphylococcus aureus and Escherichia coli under visible light illumination. Interestingly, singlet oxygen (1O2) generation by the Por-COPs can be manipulated via intramolecular regulation with the order Zn-Por-COP > OH-Por-COP > H2-Por-COP. With rationally tune, the Zn-Por-COP demonstrated remarkable antibacterial activity against Staphylococcus aureus (kill percentage 99.65 % ± 0.24 %) and Escherichia coli (kill percentage 97.25 % ± 1.78 %) in only 15 min under visible-light irradiation. Density functional theory (DFT) calculations and photophysical tests showed that the presence of electron-donating -OH groups on the aromatic linkers and Zn2+ ions in porphyrin units narrowed the HOMO-LUMO gap, enhancing both light absorption, intersystem crossing (ISC) and 1O2 generation for more efficient bacteria inactivation. This work can be applied to efficiently screen suitable photosensitizers and provides a rational regulatory strategy for PDI of pathogenic bacteria.

A dual biomarker-targeting probe enables signal-on surface labeling of Staphylococcus aureus

Imaging or killing of a specific pathogen is of significance for precise therapy. Staphylococcus aureus (S. aureus) is an infectious gram-positive bacteria relying on Sortase A (SrtA) to anchor cell surface protein on peptidoglycan. We herein report signal-on labeling of S. aureus with self-quenched optical probes featuring vancomycin-conjugated SrtA substrate that is flanked by a dabcyl moiety paired with either fluorescein or eosine photosensizer (PS). SrtA-mediated cleavage of the substrate motif releases the dabcyl quencher, leading to covalent labeling of peptidoglycan with fluorescein or PS of restored photophysical property. The dual biomarked-enabled peptidoglycan labeling enables signal-on imaging and effective photodynamic destruction of S. aureus, suggesting a protheranostic approch activatable to SrtA-positive bacteria engaged in myriad diseases.

Photoantimicrobials in agriculture

Classical approaches for controlling plant pathogens may be impaired by the development of pathogen resistance to chemical pesticides and by limited availability of effective antimicrobial agents. Recent increases in consumer awareness of and/or legislation regarding environmental and human health, and the urgent need to improve food security, are driving increased demand for safer antimicrobial strategies. Therefore, there is a need for a step change in the approaches used for controlling pre- and post-harvest diseases and foodborne human pathogens. The use of light-activated antimicrobial substances for the so-called antimicrobial photodynamic treatment is known to be effective not only in a clinical context, but also for use in agriculture to control plant-pathogenic fungi and bacteria, and to eliminate foodborne human pathogens from seeds, sprouted seeds, fruits, and vegetables. Here, we take a holistic approach to review and re-evaluate recent findings on: (i) the ecology of naturally-occurring photoantimicrobials, (ii) photodynamic processes including the light-activated antimicrobial activities of some plant metabolites, and (iii) fungus-induced photosensitization of plants. The inhibitory mechanisms of both natural and synthetic light-activated substances, known as photosensitizers, are discussed in the contexts of microbial stress biology and agricultural biotechnology. Their modes-of-antimicrobial action make them neither stressors nor toxins/toxicants (with specific modes of poisonous activity), but a hybrid/combination of both. We highlight the use of photoantimicrobials for the control of plant-pathogenic fungi and quantify their potential contribution to global food security.

Proteomic Investigation over the Antimicrobial Photodynamic Therapy Mediated by Rose Bengal Against Staphylococcus aureus

In order, to understand the antimicrobial action of photodynamic therapy and how this technique can contribute to its application in the control of pathogens. The objective of the study was to employ a proteomic approach to investigate the protein profile of S. aureus after antimicrobial photodynamic therapy mediated by rose bengal (RB-aPDT). S. aureus was treated with RB (10 nmol/l) and illuminated with green LED (0.17 J/cm² ) for cell viability evaluation. Afterward, proteomic analysis was employed for protein identification and bioinformatic tools to classify the differentially expressed proteins. The reduction of S. aureus after photoinactivation was ~2.5 log CFU/ml. A total of 12 proteins (four up-regulated and eight down-regulated), correspond exclusively to alteration by RB-aPDT. Functionally these proteins are distributed in protein binding, structural constituent of ribosome, proton transmembrane transporter activity, and ATPase activity. The effects of photodamage include alterations of levels of several proteins resulting in an activated stress response, altered membrane potential, and effects on energy metabolism. These 12 proteins required the presence of both light and RB suggesting a unique response to photodynamic effects. The information about this technique contributes valuable insights into bacterial mechanisms and the mode of action of photodynamic therapy.

Photoactivation of Erythrosine in simulated body fluids

Photodynamic Therapy (PDT) is a powerful technique for the treatment of cancer and non-cancerous diseases. The precise PDT treatment protocol definition must consider the performance difference between in vitroand in vivoapplications. This also occurs in other biological studies, and to partially overcome this difficulty, the simulated body fluids are generally applied as a prior understanding of the particularities of the different systems. However, in PDT these studies are scarce. In this work, we investigated the photoactivation of Erythrosine, a photosensitizer widely used in PDT, in different simulated body fluids. Differences in the photodegradation kinetics, triplet lifetime, and singlet oxygen generation were observed. The results can help to explain and to define PDT application protocols.

Photodynamic inactivation and its application in food preservation

Food incidents caused by various foodborne pathogenic bacteria are posing a major threat to human health. The traditional thermal and chemical-based procedures applied for microbial control in the food industry cause adverse effects on food quality and bacterial resistance. As a new means of innovative sterilization technology, photodynamic inactivation (PDI) has gained significant attention due to excellent sterilization effect, environmental friendliness, safety, and low cost. This review analyses new developments in recent years for PDI systems applied to the food preservation. The fundamentals of photosensitization mechanism, the development of photosensitizers and light source selection are discussed. The application of PDI in food preservation are presented, with the main emphasis on the natural photosensitizers and its application to inactivate in vitro and in vivo microorganisms in food matrixes such as fresh vegetable, fruits, seafood, and poultry. The challenges and future research directions facing the application of this technology to food systems have been proposed. This review will provide reference for combating microbial contamination in food industry.

Identification of New Antimicrobial Peptides from Mediterranean Medical Plant Charybdis pancration (Steinh.) Speta

The present work was designed to identify and characterize novel antimicrobial peptides (AMPs) from Charybdis pancration (Steinh.) Speta, previously named Urginea maritima, is a Mediterranean plant, well-known for its biological properties in traditional medicine. Polypeptide-enriched extracts from different parts of the plant (roots, leaves and bulb), never studied before, were tested against two relevant pathogens, Staphylococcus aureus and Pseudomonas aeruginosa. With the aim of identifying novel natural AMPs, peptide fraction displaying antimicrobial activity (the bulb) that showed minimum inhibitory concentration (MICs) equal to 30 µg/mL against the above mentioned strains, was analysed by high-resolution mass spectrometry and database search. Seventeen peptides, related to seven proteins present in the investigated database, were described. Furthermore, we focused on three peptides, which due to their net positive charge, have a better chance to be AMPs and they were investigated by molecular modelling approaches, in order to shed light on the solution properties of their equilibrium structures. Some of new detected peptides could represent a good platform for the development of new antimicrobials in the fight against antibiotic resistance phenomenon.

Application of Response Surface Methodology to Evaluate Photodynamic Inactivation Mediated by Eosin Y and 530 nm LED against Staphylococcus aureus

Photodynamic antimicrobial chemotherapy (PAC) is an efficient tool for inactivating microorganisms. This technique is a good approach to inactivate the foodborne microorganisms, which are responsible for one of the major public health concerns worldwide—the foodborne diseases. In this work, response surface methodology (RSM) was used to evaluate the interaction of Eosin Y (EOS) concentration and irradiation time on Staphylococcus aureus counts and a sequence of designed experiments to model the combined effect of each factor on the response. A second-order polynomial empirical model was developed to describe the relationship between EOS concentration and irradiation time. The results showed that the derived model could predict the combined influences of these factors on S. aureus counts. The agreement between predictions and experimental observations (R²_adj = 0.9159, p = 0.000034) was also observed. The significant terms in the model were the linear negative effect of photosensitizer (PS) concentration, followed by the linear negative effect of irradiation time, and the quadratic negative effect of PS concentration. The highest reductions in S. aureus counts were observed when applying a light dose of 9.98 J/cm² (498 nM of EOS and 10 min. irradiation). The ability of the evaluated model to predict the photoinactivation of S. aureus was successfully validated. Therefore, the use of RSM combined with PAC is a promising approach to inactivate foodborne pathogens.

The Remarkable Effect of Potassium Iodide in Eosin and Rose Bengal Photodynamic Action against Salmonella Typhimurium and Staphylococcus aureus

Antimicrobial photodynamic therapy (aPDT) has been shown as a promising technique to inactivate foodborne bacteria, without inducing the development of bacterial resistance. Knowing that addition of inorganic salts, such as potassium iodide (KI), can modulate the photodynamic action of the photosensitizer (PS), we report in this study the antimicrobial effect of eosin (EOS) and rose bengal (RB) combined with KI against Salmonella enterica serovar Typhimurium and Staphylococcus aureus. Additionally, the possible development of bacterial resistance after this combined aPDT protocol was evaluated. The combination of EOS or RB, at all tested concentrations, with KI at 100 mM, was able to efficiently inactivate S. Typhimurium and S. aureus. This combined approach allows a reduction in the PS concentration up to 1000 times, even against one of the most common foodborne pathogenics, S. Typhimurium, a gram-negative bacterium which is not so prone to inactivation with xanthene dyes when used alone. The photoinactivation of S. Typhimurium and S. aureus by both xanthenes with KI did not induce the development of resistance. The low price of the xanthene dyes, the non-toxic nature of KI, and the possibility of reducing the PS concentration show that this technology has potential to be easily transposed to the food industry.

Photodynamic inactivation of S. aureus with a water-soluble curcumin salt and an application to cheese decontamination

In this study, the optimal parameters for the photodynamic inactivation (PDI) of Staphylococcus aureus in bacterial suspensions and in cheese were assessed using a water-soluble curcumin salt as the photosensitizer (PS).

Antimicrobial Photodynamic Inactivation Mediated by Rose Bengal and Erythrosine Is Effective in the Control of Food-Related Bacteria in Planktonic and Biofilm States

The thermal and chemical-based methods applied for microbial control in the food industry are not always environmentally friendly and may change the nutritional and organoleptic characteristics of the final products. Moreover, the efficacy of sanitizing agents may be reduced when microbial cells are enclosed in biofilms. The objective of this study was to investigate the effect of photodynamic inactivation, using two xanthene dyes (rose bengal and erythrosine) as photosensitizing agents and green LED as a light source, against Staphylococcus aureus, Listeria innocua, Enterococcus hirae and Escherichia coli in both planktonic and biofilm states. Both photosensitizing agents were able to control planktonic cells of all bacteria tested. The treatments altered the physicochemical properties of cells surface and also induced potassium leakage, indicating damage of cell membranes. Although higher concentrations of the photosensitizing agents (ranging from 0.01 to 50.0 μmol/L) were needed to be applied, the culturability of biofilm cells was reduced to undetectable levels. This finding was confirmed by the live/dead staining, where propidium iodide-labeled bacteria numbers reached up to 100%. The overall results demonstrated that photoinactivation by rose bengal and erythrosine may be a powerful candidate for the control of planktonic cells and biofilms in the food sector.