Plasma-Activated Water Against Carbapenem-Resistant Klebsiella pneumoniae and Vancomycin-Resistant Enterococcus faecalis

The scope of the antibacterial effects of plasma-activated water (PAW) is not yet fully comprehended. We investigated the activity of PAW produced by the in-house 3-pin atmospheric pressure plasma jet against carbapenem-resistant Klebsiella pneumoniae and vancomycin-resistant Enterococcus faecalis, with a focus on PAW's potential to promote susceptibility to conventional antibiotics in these bacteria. Bacterial inactivation was determined by the colony count after 15 and 60 min PAW treatments. Minimum inhibitory concentrations (MICs) measured following repeated exposures to PAW across multiple generations of bacteria enabled the assessment of changes in susceptibility to antibiotics. The PAW's efficacy was also analyzed through the detection of intracellular reactive oxygen and nitrogen species in treated bacteria. Time-dependent significant inactivation efficiency against K. pneumoniae was observed (log reduction 6.92 ± 0.24 after 60 min exposure), while effects on E. faecalis were limited. PAW demonstrated potential to decrease the MICs of crucial antibiotics. Namely, a 50 to 62.5% decrease in the MICs of colistin against K. pneumoniae and a 25% reduction in the MICs of vancomycin against enterococci were recorded. We found a significant increase in the superoxide anion concentration in K. pneumoniae and E. faecalis cells after PAW treatments. This study indicates that PAW's inactivating efficacy coupled with the capacity for the potentiation of antibiotic effects is a promising combination against multidrug-resistant bacteria.

Cold Plasma Activity Against Biofilm Formation of Prosthetic Joint Infection Pathogens

Periprosthetic joint infections occur in 1-2% of all patients undergoing prosthetic joint surgeries. Although strong efforts have been made to reduce infection rates, conventional therapies like one- or two-stage revisions have failed to lower the infection rates. Cold atmospheric plasma (CAP) has shown promising results in reducing bacterial loads on surfaces. In this study, we aimed to investigate the ability of CAP to reduce the bacterial load on metal surfaces with varying distances and different plasma compositions below a temperature suitable for in vivo applications. Methods: Biofilm was formed with Staphylococcus aureus ATCC 29213 and Staphylococcus epidermidis ATCC 12228 cultures on TMZF discs. Plasma treatments using air plasma and argon plasma were conducted on discs containing the established biofilm while the temperature was measured. During the experiments, the duration and the distance of plasma application varied. Afterwards, colony-forming units were counted. Results: The results of this study showed that air and argon plasma could be considered for applications during surgeries at a 1 cm distance. While air plasma showed the highest efficiency in CFU reduction, the temperature generation due to the presence of oxygen poses a limitation concerning the duration of application. The use of argon as a plasma generator does not show the temperature limitation in correlation to exposure time. The use of air plasma with a distance of 1 cm to the application site and an exposure time of 5 s showed the most effective bacterial reduction while not exceeding tissue-damaging temperatures.

Antimicrobial Activity of Cold Atmospheric Plasma on Bacterial Strains Derived from Patients with Diabetic Foot Ulcers

Bacterial infections or their biofilms in diabetic foot ulcer (DFU) are a key cause of drug-resistant wounds and amputations. Cold atmospheric plasma (CAP) is well documented for its antibacterial effect and promoting wound healing. In the current study, we built an argon-based, custom CAP device and investigated its potential in eliminating laboratory and clinical bacterial strains derived from DFU. The CAP device performed as expected with generation of hydroxyl, reactive nitrogen species, and argon species as determined by optical emission spectroscopy. A dose-dependent increase in oxidation reduction potential (ORP) and nitrites in the liquid phase was observed. The CAP treatment eliminated both gram-positive (Staphylococcus aureus, Entrococcus faecalis) and negative bacteria (Pseudomonas aeruginosa, Proteus mirabilis) laboratory strains. Clinical samples collected from DFU patients exhibited a significant decrease in both types of bacteria, with gram-positive strains showing higher susceptibility to the CAP treatment in an ex vivo setting. Moreover, exposure to CAP of polymicrobial biofilms from DFU led to a notable disruption in biofilm and an increase in free bacterial DNA. The duration of CAP exposure used in the current study did not induce DNA damage in peripheral blood lymphocytes. These results suggest that CAP could serve as an excellent tool in treating patients with DFUs.

Plasma-Functionalized Liquids for Decontamination of Viable Tissues: A Comparative Approach

Plasma-functionalized liquids (PFLs) are rich in chemical species, such as ozone, hydrogen peroxide, singlet oxygen, hydroxyl radical and nitrogen oxides, commonly referred to as reactive oxygen and nitrogen species (RONS). Therefore, manifold applications are being investigated for their use in medicine, agriculture, and the environment. Depending on the goal, a suitable plasma source concept for the generation of PFLs has to be determined because the plasma generation setup determines the composition of reactive species. This study investigates three PFL-generating plasma sources-two spark discharges and a flow dielectric barrier discharge (DBD) system-for their efficacy in eliminating microbial contaminants from tissue samples aiming to replace antibiotics in the rinsing process. The final goal is to use these tissues as a cell source for cell-based meat production in bioreactors and thereby completely avoid antibiotics. Initially, a physicochemical characterization was conducted to better understand the decontamination capabilities of PFLs and their potential impact on tissue viability. The results indicate that the flow DBD system demonstrated the highest antimicrobial efficacy due to its elevated reactive species output and the possibility of direct treatment of tissues while tissue integrity remained. Achieving a balance between effective large-scale decontamination and the biocompatibility of PFLs remains a critical challenge.

Sprayable, thermosensitive hydrogels for promoting wound healing based on hollow, porous and pH-sensitive ZnO microspheres

A solvothermal method and the subsequent heat treatment process were developed to fabricate hollow ZnO particles with hierarchical pores on a large scale. The as-obtained hollow, porous ZnO microspheres with tunable sizes, high specific surface areas, pH sensitivity, antibacterial properties, and high adsorption capacities showed significant advantages for drug delivery. Sprayable hydrogels containing hollow, porous ZnO microspheres and curcumin nanoparticles (CNPs) were prepared to accelerate wound healing. The water-dispersed CNPs promoted both the migration of fibroblasts and angiogenesis and an aqueous solution of Pluronic F127 (a temperature-sensitive phase-change hydrogel material) was shown to be an effective choice for medical dressings. The experimental data suggest that hollow, porous ZnO microspheres can be loaded with additional CNPs to achieve continuous long-term therapeutic effects.

In-package cold plasma treatment to extend the shelf life of food

Conventional food preservation methods such as heat treatment, irradiation, chemical treatment, refrigeration, and coating have various disadvantages, like loss of food quality, nutrition, and cost-effectiveness. Accordingly, cold plasma is one of the new technologies for food processing and has played an important role in preventing food spoilage. Specifically, in-package cold plasma has become a modern trend to decontaminate, process, and package food simultaneously. This strategy has proven successful in processing various fresh food ingredients, including spinach, fruits, vegetables, and meat. In particular, cold plasma treatment within the package reduces the risk of post-processing contamination. Cryoplasm decontamination within packaging has been reported to reduce significantly the microbial load of many foods' spoilage-causing pathogens. However, studies are needed to focus more on the effects of in-package treatments on endogenous enzyme activity, pest control, and removal of toxic pesticide residues. In this review, we comprehensively evaluated the efficacy of in-package low-temperature plasma treatment to extend the shelf life of various foods. The mechanisms by which cold plasma interacts with food were investigated, emphasizing its effects on pathogen reduction, spoilage mitigation, and surface modification. The review also critically assessed the effects of the treatments on food quality, regulatory considerations, and their potential as viable technologies to improve food safety and packaging life. In-package cold plasma treatment could revolutionize food storage when combined with other sophisticated technologies such as nanotechnology.

The Preparation of Silver and Gold Nanoparticles in Hyaluronic Acid and the Influence of Low-Pressure Plasma Treatment on Their Physicochemical and Microbiological Properties

Nanometals constitute a rapidly growing area of research within nanotechnology. Nanosilver and nanogold exhibit significant antimicrobial, antifungal, antiviral, anti-inflammatory, anti-angiogenic, and anticancer properties. The size and shape of nanoparticles are critical for determining their antimicrobial activity. In this study, silver and gold nanoparticles were synthesized within a hyaluronic acid matrix utilizing distilled water and distilled water treated with low-pressure, low-temperature glow plasma in an environment of air and argon. Electron microscopy, UV-Vis and FTIR spectra, water, and mechanical measurements were conducted to investigate the properties of nanometallic composites. This study also examined their microbiological properties. This study demonstrated that the properties of the composites differed depending on the preparation conditions, encompassing physicochemical and microbiological properties. The application of plasma-treated water under both air and argon had a significant effect on the size and distribution of nanometals. Silver nanoparticles were obtained between the range of 5 to 25 nm, while gold nanoparticles varied between 10 to 35 nm. The results indicate that the conditions under which silver and gold nanoparticles are produced have a significant effect on their mechanical and antibacterial properties.

The bactericidal effect of two photoactivated chromophore for keratitis-corneal crosslinking protocols (standard vs. accelerated) on bacterial isolates associated with infectious keratitis in companion animals

Background

Bacterial corneal infections are common and potentially blinding diseases in all species. As antibiotic resistance is a growing concern, alternative treatment methods are an important focus of research. Photoactivated chromophore for keratitis-corneal crosslinking (PACK-CXL) is a promising oxygen radical-mediated alternative to antibiotic treatment. The main goal of this study was to assess the anti-bactericidal efficacy on clinical bacterial isolates of the current standard and an accelerated PACK-CXL treatment protocol delivering the same energy dose (5.4 J/cm²).

Methods

Clinical bacterial isolates from 11 dogs, five horses, one cat and one guinea pig were cultured, brought into suspension with 0.1% riboflavin and subsequently irradiated. Irradiation was performed with a 365 nm UVA light source for 30 min at 3mW/cm² (standard protocol) or for 5 min at 18mW/cm² (accelerated protocol), respectively. After treatment, the samples were cultured and colony forming units (CFU’s) were counted and the weighted average mean of CFU’s per μl was calculated. Results were statistically compared between treated and control samples using a linear mixed effects model.

Results

Both PACK-CXL protocols demonstrated a significant bactericidal effect on all tested isolates when compared to untreated controls. No efficacy difference between the two PACK-CXL protocols was observed.

Conclusion

The accelerated PACK-CXL protocol can be recommended for empirical use in the treatment of bacterial corneal infections in veterinary patients while awaiting culture results. This will facilitate immediate treatment, the delivery of higher fluence PACK-CXL treatment within a reasonable time, and minimize the required anesthetic time or even obviate the need for general anesthesia.

Improving Vascularization of Biomaterials for Skin and Bone Regeneration by Surface Modification: A Narrative Review on Experimental Research

Artificial tissue substitutes are of great interest for the reconstruction of destroyed and non-functional skin or bone tissue due to its scarcity. Biomaterials used as scaffolds for tissue regeneration are non-vascularized synthetic tissues and often based on polymers, which need ingrowth of new blood vessels to ensure nutrition and metabolism. This review summarizes previous approaches and highlights advances in vascularization strategies after implantation of surface-modified biomaterials for skin and bone tissue regeneration. The efficient integration of biomaterial, bioactive coating with endogenous degradable matrix proteins, physiochemical modifications, or surface geometry changes represents promising approaches. The results show that the induction of angiogenesis in the implant site as well as the vascularization of biomaterials can be influenced by specific surface modifications. The neovascularization of a biomaterial can be supported by the application of pro-angiogenic substances as well as by biomimetic surface coatings and physical or chemical surface activations. Furthermore, it was confirmed that the geometric properties of the three-dimensional biomaterial matrix play a central role, as they guide or even enable the ingrowth of blood vessels into a biomaterial.

Recent trends and technological development in plasma as an emerging and promising technology for food biosystems

The rising need for wholesome, fresh, safe and “minimally-processed” foods has led to pioneering research activities in the emerging non-thermal technology of food processing. Cold plasma is such an innovative and promising technology that offers several potential applications in the food industry. It uses the highly reactive, energetic and charged gas molecules and species to decontaminate the food and package surfaces and preserve the foods without causing thermal damage to the nutritional and quality attributes of food. Cold plasma technology showed promising results about the inactivation of pathogens in the food industry without affecting the food quality. It is highly effective for surface decontamination of fruits and vegetables, but extensive research is required before its commercial utilization. Recent patents are focused on the applications of cold plasma in food processing and preservation. However, further studies are strongly needed to scale up this technology for future commercialization and understand plasma physics for getting better results and expand the applications and benefits. This review summarizes the emerging trends of cold plasma along with its recent applications in the food industry to extend shelf life and improve the quality of food. It also gives an overview of plasma generation and principles including mechanism of action. Further, the patents based on cold plasma technology have also been highlighted comprehensively for the first time.

Experimental Evaluation of the Effect of Argon Cold Plasma on Oxidative Metabolism of the Blood

We studied the effect of course exposure to argon cold plasma (ten 1- and 2-min procedures) on some parameters of the oxidative metabolism of rat blood plasma. The intensity of free radical processes, the total antioxidant activity, and malondialdehyde concentration in rat plasma were evaluated. It was found that 2-min exposure to argon cold plasma and nonionized argon stream produce a prooxidant effect, while 1-min exposure argon plasma led to stimulation of the antioxidant reserves of the blood.

Non-Thermal Atmospheric Plasma for Microbial Decontamination and Removal of Hazardous Chemicals: An Overview in the Circular Economy Context with Data for Test Applications of Microwave Plasma Torch

The transformation of our linear “take-make-waste” system to a cyclic flow of materials and energy is a priority task for society, but the circular use of waste streams from one industry/sector as a material input for another must be completely safe. The need for new advanced technologies and methods ensuring both microbiological safety and the removal of potential chemical residues in used materials and products is urgent. Non-thermal atmospheric plasma (cold atmospheric plasma—CAP) has recently attracted great research interest as an alternative for operative solutions of problems related to safety and quality control. CAP is a powerful tool for the inactivation of different hazardous microorganisms and viruses, and the effective decontamination of surfaces and liquids has been demonstrated. Additionally, the plasma’s active components are strong oxidizers and their synergetic effect can lead to the degradation of toxic chemical compounds such as phenols and azo-dyes.

Chronic wounds treated with cold atmospheric plasmajet versus best practice wound dressings: a multicenter, randomized, non-inferiority trial

The use of phase-adapted wound dressings represents best practice (BP) in chronic wound treatment. However, efficacy is often limited and associated care requirements are high. Cold atmospheric plasmajet (CAP-jet) is a promising new therapeutic tool for these wounds. In the present multicenter, randomized, open-label, prospective, clinical trial, non-inferiority of the CAP-jet versus BP was assessed in 78 patients with infected or non-infected chronic wounds of different etiology. Primary outcome measure was the sum of granulation tissue, furthermore wound area reduction, healing rate, time to complete healing, changes in wound pH value, infection score, exudate level and local tolerability were assessed. In CAP-jet treated wounds compared to control, the sum of granulation tissue was significantly higher (p < 0.0001) and wound area reduced significantly faster (p < 0.001). Furthermore, wound pH value decreased significantly faster (p = 0.0123) and local infection was overcome more rapidly by CAP-jet therapy. In 58.97% CAP-jet- vs. 5.13% BP-treated patients, complete healing of chronic ulcers was documented after 6 weeks. Treatment with CAP-jet appeared not only non-inferior, but even superior to BP in all wound entities analyzed with a favorable tolerability profile. Thus, treatment with the CAP-jet provides beneficial effects in chronic wound treatment regarding promotion of the wound healing process.

Progress in Alternative Strategies to Combat Antimicrobial Resistance: Focus on Antibiotics

Antibiotic resistance, and, in a broader perspective, antimicrobial resistance (AMR), continues to evolve and spread beyond all boundaries. As a result, infectious diseases have become more challenging or even impossible to treat, leading to an increase in morbidity and mortality. Despite the failure of conventional, traditional antimicrobial therapy, in the past two decades, no novel class of antibiotics has been introduced. Consequently, several novel alternative strategies to combat these (multi-) drug-resistant infectious microorganisms have been identified. The purpose of this review is to gather and consider the strategies that are being applied or proposed as potential alternatives to traditional antibiotics. These strategies include combination therapy, techniques that target the enzymes or proteins responsible for antimicrobial resistance, resistant bacteria, drug delivery systems, physicochemical methods, and unconventional techniques, including the CRISPR-Cas system. These alternative strategies may have the potential to change the treatment of multi-drug-resistant pathogens in human clinical settings.

Antibacterial efficacy of non-thermal atmospheric plasma against Streptococcus mutans biofilm grown on the surfaces of restorative resin composites

The aim of this study was to evaluate the antimicrobial efficacy of non-thermal atmospheric plasma (NTAP) against Streptococcus mutans biofilms. Resin discs were fabricated, wet-polished, UV sterilized, and immersed in water for monomer extraction (37 °C, 24 h). Biofilms of bioluminescent S. mutans strain JM10 was grown on resin discs in anaerobic conditions for (37 °C, 24 h). Discs were divided into seven groups: control (CON), 2% chlorhexidine (CHX), only argon gas 150 s (ARG) and four NTAP treatments (30 s, 90 s, 120 s, 150 s). NTAP was applied using a plasma jet device. After treatment, biofilms were analyzed through the counting of viable colonies (CFU), bioluminescence assay (BL), scanning electron microscopy (SEM), and polymerase chain reaction (PCR). All NTAP-treated biofilm yielded a significant CFU reduction when compared to ARG and CON. BL values showed that NTAP treatment for 90 s, 120 s or 150 s resulted in statistically significantly lower metabolic activity when compared to the other groups. CHX displayed the lowest means of CFU and BL. SEM showed significant morphological changes in NTAP-treated biofilm. PCR indicated damage to the DNA structure after NTAP treatment. NTAP treatment was effective in lowering the viability and metabolism of S. mutans in a time-dependent manner, suggesting its use as an intraoral surface-decontamination strategy.

In vitro antibacterial and antibiofilm effects of cold atmospheric microwave plasma against Pseudomonas aeruginosa causing canine skin and ear infections

BACKGROUND

Pseudomonas aeruginosa is an opportunist pathogen that causes purulent inflammation in the skin and in the ears of dogs. Among the various virulence factors of P. aeruginosa, biofilms have been reported to result in antibiotic resistance, leading to therapeutic limitations. Cold atmospheric microwave plasma (CAMP) is known to have a high antimicrobial effect, which causes physical cell wall rupture and DNA damage.

HYPOTHESIS/OBJECTIVES

The objective of this study was to evaluate the antibacterial and antibiofilm effects of CAMP against planktonic bacteria and the biofilm of P. aeruginosa.

METHODS AND MATERIALS

The antibacterial effect of CAMP against P. aeruginosa ATCC10145 and clinical isolates (n = 30) was evaluated using the colony count method. We also assessed the effect of CAMP on biofilm of P. aeruginosa ATCC strain by the colony count method, water-soluble tetrazolium salt (WST) assay and confocal laser scanning microscopy (CLSM).

RESULTS

The complete eradication of P. aeruginosa (ATCC strain and clinical isolates) was achieved within 120 s at 50 W, and clinical isolates required 60 s shorter than the ATCC strain for complete eradication at 50 W. We also confirmed the time-dependent bactericidal effect of CAMP at 50 W against ATCC strain biofilm.

CONCLUSIONS AND CLINICAL IMPORTANCE

CAMP was effective against both planktonic bacteria and biofilm formation of P. aeruginosa. However, further studies on in vivo efficacy and safety in canine skin and ears are necessary to fully validate its clinical application.

Non-thermal Plasma Treatment of ESKAPE Pathogens: A Review

The acronym ESKAPE refers to a group of bacteria consisting of Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp. They are important in human medicine as pathogens that show increasing resistance to commonly used antibiotics; thus, the search for new effective bactericidal agents is still topical. One of the possible alternatives is the use of non-thermal plasma (NTP), a partially ionized gas with the energy stored particularly in the free electrons, which has antimicrobial and anti-biofilm effects. Its mechanism of action includes the formation of pores in the bacterial membranes; therefore, resistance toward it is not developed. This paper focuses on the current overview of literature describing the use of NTP as a new promising tool against ESKAPE bacteria, both in planktonic and biofilm forms. Thus, it points to the fact that NTP treatment can be used for the decontamination of different types of liquids, medical materials, and devices or even surfaces used in various industries. In summary, the use of diverse experimental setups leads to very different efficiencies in inactivation. However, Gram-positive bacteria appear less susceptible compared to Gram-negative ones, in general.

In vitro antimicrobial activity of cold atmospheric microwave plasma against bacteria causing canine skin and ear infections

BACKGROUND

Cold atmospheric plasma (CAP) is a new generation medical therapeutic option for bacterial infections. CAP causes physical cell wall rupture and DNA damage, therefore making it highly useful in the treatment of various conditions such as skin infections.

HYPOTHESIS/OBJECTIVES

The antimicrobial activity of cold atmospheric microwave plasma (CAMP) against major strains in canine skin infections was tested and the difference in antimicrobial activity between the antibiotic-resistant and antibiotic-susceptible strains of Staphylococcus pseudintermedius was evaluated.

METHODS AND MATERIALS

American Type Culture Collection (ATCC) strains (Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli) and clinical isolates identified as methicillin-resistant S. pseudintermedius (n = 27) and methicillin-susceptible S. pseudintermedius (n = 13) were exposed to CAMP for 10 s, 30 s and 60 s. Afterwards, the bacterial survival rate was confirmed.

RESULTS

Gram-negative bacteria (P. aeruginosa and E. coli) were more susceptible than Gram-positive bacteria (S. aureus and S. pseudintermedius) for the same duration of CAMP exposure. Only the Gram-negative bacteria were completely killed after 60 s exposure. In S. pseudintermedius isolates, CAMP exposure had similar antibacterial effects regardless of antibiotic resistance.

CONCLUSIONS AND CLINICAL IMPORTANCE

CAMP has sufficient antimicrobial activity against major bacterial strains that cause pyoderma and otitis externa in dogs, and may be an alternative therapeutic option for S. pseudintermedius skin infections, for which antibiotics often are ineffective because of antimicrobial resistance in clinical veterinary medicine.

Inactivation of Staphylococcus aureus and Escherichia coli Biofilms by Air-Based Atmospheric-Pressure DBD Plasma

Air-based atmospheric-pressure plasma is an effective non-thermal method in deactivating various kinds of microbial biofilms with several advantages, including high bactericidal efficiency and low treatment costs. Bacterial biofilm formation is a major determinant in establishment of bacterial infection and also resistance to antibacterial chemotherapy. This study aims to assess the anti-biofilm potential of air-based atmospheric-pressure DBD plasma against Staphylococcus aureus and Escherichia coli biofilms. The biofilms of Staphylococcus aureus and Escherichia coli were exposed to air-based atmospheric-pressure DBD plasma for up to 4 min (control, 30 s, 90 s, 3 min, and 4 min) and their biofilm formation level, viability, and membrane integrity were determined. Based on the results, plasma exposure caused disruption up to 70% and 85% for S. aureus and E. coli biofilms, respectively. The biofilm disruption potential of air-based atmospheric-pressure DBD plasma was confirmed using the scanning electron microscopy (SEM). Besides, based on confocal laser scanning microscopy (CLSM), plasma exposure caused a significant bacterial inactivation and E. coli was found as more susceptible strain than S. aureus. In conclusion, atmospheric-pressure DBD plasma could be considered an efficient non-thermal approach against bacterial pathogenicity by biofilm disruption and thus prevention of infection establishment.

Validation of process technologies for enhancing the safety of low-moisture foods: A review

The outbreaks linked to foodborne illnesses in low-moisture foods are frequently reported due to the occurrence of pathogenic microorganisms such as Salmonella Spp. Bacillus cereus, Clostridium spp., Cronobacter sakazakii, Escherichia coli, and Staphylococcus aureus. The ability of the pathogens to withstand the dry conditions and to develop resistance to heat is regarded as the major concern for the food industry dealing with low-moisture foods. In this regard, the present review is aimed to discuss the importance and the use of novel thermal and nonthermal technologies such as radiofrequency, steam pasteurization, plasma, and gaseous technologies for decontamination of foodborne pathogens in low-moisture foods and their microbial inactivation mechanisms. The review also summarizes the various sources of contamination and the factors influencing the survival and thermal resistance of pathogenic microorganisms in low-moisture foods. The literature survey indicated that the nonthermal techniques such as CO₂ , high-pressure processing, and so on, may not offer effective microbial inactivation in low-moisture foods due to their insufficient moisture content. On the other hand, gases can penetrate deep inside the commodities and pores due to their higher diffusion properties and are regarded to have an advantage over thermal and other nonthermal processes. Further research is required to evaluate newer intervention strategies and combination treatments to enhance the microbial inactivation in low-moisture foods without significantly altering their organoleptic and nutritional quality.

Cold Atmospheric Plasma Promotes Killing of Staphylococcus aureus by Macrophages

Macrophages are important immune cells that are involved in the elimination of microbial pathogens. Following host invasion, macrophages are recruited to the site of infection, where they launch antimicrobial defense mechanisms. Effective microbial clearance by macrophages depends on phagocytosis and phagolysosomal killing mediated by oxidative burst, acidification, and degradative enzymes. However, some pathogenic microorganisms, including some drug-resistant bacteria, have evolved sophisticated mechanisms to prevent phagocytosis or escape intracellular degradation. Cold atmospheric plasma (CAP) is an emerging technology with promising bactericidal effects. Here, we investigated the effect of CAP on Staphylococcus aureus phagocytosis by RAW 264.7 macrophage-like cells. We demonstrate that CAP treatment increases intracellular concentrations of reactive oxygen species (ROS) and nitric oxide and promotes the elimination of both antibiotic-sensitive and antibiotic-resistant S. aureus by RAW 264.7 cells. This effect was inhibited by antioxidants indicating that the bactericidal effect of CAP was mediated by oxidative killing of intracellular bacteria. Furthermore, we show that CAP promotes the association of S. aureus to lysosomal-associated membrane protein 1 (LAMP-1)-positive phagosomes, in which bacteria are exposed to low pH and cathepsin D hydrolase. Taken together, our results provide the first evidence that CAP activates defense mechanisms of macrophages, ultimately leading to bacterial elimination. IMPORTANCE Staphylococcus aureus is the most frequent cause of skin and soft tissue infections. Treatment failures are increasingly common due to antibiotic resistance and the emergence of resistant strains. Macrophages participate in the first line of immune defense and are critical for coordinated defense against pathogenic bacteria. However, S. aureus has evolved sophisticated mechanisms to escape macrophage killing. In the quest to identify novel antimicrobial therapeutic approaches, we investigated the activity of cold atmospheric plasma (CAP) on macrophages infected with S. aureus. Here, we show that CAP treatment promotes macrophage ability to eliminate internalized bacteria. Importantly, CAP could trigger killing of both antibiotic-sensitive and antibiotic-resistant strains of S. aureus. While CAP did not affect the internalization capacity of macrophages, it increased oxidative-dependent bactericidal activity and promoted the formation of degradative phagosomes. Our study shows that CAP has beneficial effects on macrophage defense mechanisms and may potentially be useful in adjuvant antimicrobial therapies.

Effects of non-thermal atmospheric pressure plasma on palatal wound healing of free gingival grafts: a randomized controlled clinical trial

OBJECTIVE

The aim of this trial was to evaluate the effects of non-thermal atmospheric pressure plasma (NAPP) on wound healing, epithelization, local pain, bleeding, and alteration of sensation in palatal donor site.

MATERIALS AND METHODS

Forty patients with inadequate attached gingiva were included in the study. Patients were divided into two groups: (i) NAPP group (Free gingival graft [FGG] + NAPP) and (ii) control group (FGG alone). NAPP was performed immediately after the operation and on days 3 and 7. Pain, bleeding, and the amount of medication were recorded by patients every day. Epithelization in donor site, alteration of sensation and color match were assessed weekly for 2 months. Inter-group comparisons of continuous variables by time were performed with two-way repeated measures ANOVA test and a general linear model. Categorical variables were compared using Chi-square exact test. A p value of < 0.05 was considered significant.

RESULTS

At week 2, the number of patients with complete epithelization was greater in the NAPP group compared to the control group (p < 0.05). Additionally, color match in donor site was better in the NAPP group than in the control group (p < 0.05) during the first five follow-up assessments. No significant difference was found between the two groups with regard to bleeding, pain level, drug use, and alteration of sensation.

CONCLUSION

The NAPP application increased the epithelization and accelerated the wound healing process although it did not decrease the level of pain and sensation.

CLINICAL RELEVANCE

Our data suggested that the NAPP application may help epithelization and thus may shorten the recovery time after oral surgeries.

Plasma bioscience and its application to medicine

Nonthermal atmospheric pressure biocompatible plasma (NBP), alternatively called bio-cold plasma, is a partially ionized gas that consists of charged particles, neutral atoms and molecules, photons, an electric field, and heat. Recently, nonthermal plasma-based technology has been applied to bioscience, medicine, agriculture, food processing, and safety. Various plasma device configurations and electrode layouts has fast-tracked plasma applications in the treatment of biological and material surfaces. The NBP action mechanism may be related to the synergy of plasma constituents, such as ultraviolet radiation or a reactive species. Recently, plasma has been used in the inactivation of viruses and resistant microbes, such as fungal cells, bacteria, spores, and biofilms made by microbes. It has also been used to heal wounds, coagulate blood, degrade pollutants, functionalize material surfaces, kill cancers, and for dental applications. This review provides an outline of NBP devices and their applications in bioscience and medicine. We also discuss the role of plasma-activated liquids in biological applications, such as cancer treatments and agriculture. The individual adaptation of plasma to meet specific medical requirements necessitates real-time monitoring of both the plasma performance and the target that is treated and will provide a new paradigm of plasma-based therapeutic clinical systems.

The antimicrobial efficacy of remote cold atmospheric plasma effluent against single and mixed bacterial biofilms of varying age

Cold atmospheric plasma (CAP) is a minimal food processing technology of increasing interest in the food industry, as it is mild in nature compared to traditional methods (e.g. pasteurisation) and thus can maintain the food's desirable qualities. However, due to this mild nature, the potential exists for post-treatment microbial survival and/or stress adaptation. Furthermore, biofilm inactivation by CAP is underexplored and mostly studied on specific foods or on plastic/polymer surfaces. Co-culture effects, biofilm age, and innate biofilm-associated resistance could all impact CAP efficacy, while studies on real foods are limited to the food product investigated without accounting for structural complexity. The effect of a Remote and Enclosed CAP device (Fourth State Medicine Ltd) was investigated on Escherichia coli and Listeria innocua grown as planktonic cells and as single or mixed bacterial biofilms of variable age, on a biphasic viscoelastic food model of controlled rheological and structural complexity. Post-CAP viability was assessed by plate counts, cell sublethal injury was quantified using flow cytometry, and biofilms were characterised and assessed using total protein content and microscopy techniques. A greater impact of CAP on planktonic cells was observed at higher air flow rates, where the ReCAP device operates in a mode more favourable to reactive oxygen species than reactive nitrogen species. Although planktonic E. coli was more susceptible to CAP than planktonic L. innocua, the opposite was observed in biofilm form. The efficacy of CAP was reduced with increasing biofilm age. Furthermore, E. coli produced much higher protein content in both single and mixed biofilms than L. innocua. Consequently, greater survival of L. innocua in mixed biofilms was attributed to a protective effect from E. coli. These results show that biofilm susceptibility to CAP is age and bacteria dependent, and that in mixed biofilms bacteria may become less susceptible to CAP. These findings are of significance to the food industry for the development of effective food decontamination methods using CAP.

The Antimicrobial Effect of Cold Atmospheric Plasma against Dental Pathogens-A Systematic Review of In-Vitro Studies

Interest in the application of cold atmospheric plasma (CAP) in the medical field has been increasing. Indications in dentistry are surface modifications and antimicrobial interventions. The antimicrobial effect of CAP is mainly attributed to the generation of reactive oxygen and reactive nitrogen species. The aim of this article is to systematically review the available evidence from in-vitro studies on the antimicrobial effect of CAP on dental pathogens. A database search was performed (PubMed, Embase, Scopus). Data concerning the device parameters, experimental set-ups and microbial cultivation were extracted. The quality of the studies was evaluated using a newly designed assessment tool. 55 studies were included (quality score 31-92%). The reduction factors varied strongly among the publications although clusters could be identified between groups of set pathogen, working gases, and treatment time intervals. A time-dependent increase of the antimicrobial effect was observed throughout the studies. CAP may be a promising alternative for antimicrobial treatment in a clinically feasible application time. The introduced standardized protocol is able to compare the outcome and quality of in-vitro studies. Further studies, including multi-species biofilm models, are needed to specify the application parameters of CAP before CAP should be tested in randomized clinical trials.

Distinct Chemistries Define the Diverse Biological Effects of Plasma Activated Water Generated with Spark and Glow Plasma Discharges

The spread of multidrug-resistant bacteria poses a significant threat to human health. Plasma activated liquids (PAL) could be a promising alternative for microbial decontamination, where different PAL can possess diverse antimicrobial efficacies and cytotoxic profiles, depending on the range and concentration of their reactive chemical species. In this research, the biological activity of plasma activated water (PAW) on different biological targets including both microbiological and mammalian cells was investigated in vitro. The aim was to further an understanding of the specific role of distinct plasma reactive species, which is required to tailor plasma activated liquids for use in applications where high antimicrobial activity is required without adversely affecting the biology of eukaryotic cells. PAW was generated by glow and spark discharges, which provide selective generation of hydrogen peroxide, nitrite and nitrate in the liquid. The PAW made by either spark or glow discharges showed similar antimicrobial efficacy and stability of activity, despite the very different reactive oxygen species (ROS) and reactive nitrogen species profiles (RNS). However, different trends were observed for cytotoxic activities and effects on enzyme function, which were translated through the selective chemical species generation. These findings indicate very distinct mechanisms of action which may be exploited when tailoring plasma activated liquids to various applications. A remarkable stability to heat and pressure was noted for PAW generated with this set up, which broadens the application potential. These features also suggest that post plasma modifications and post generation stability can be harnessed as a further means of modulating the chemistry, activity and mode of delivery of plasma functionalised liquids. Overall, these results further understanding on how PAL generation may be tuned to provide candidate disinfectant agents for biomedical application or for bio-decontamination in diverse areas.

Safety and efficacy of cold atmospheric plasma for the sterilization of a Pasteurella multocida-contaminated subcutaneously implanted foreign body in rabbits

OBJECTIVE

To determine whether a stainless steel implant sterilized with a novel cold atmospheric plasma sterilization (CAPS) device adversely affects local tissues in rabbits and whether CAPS was as effective as steam sterilization with an autoclave to inactivate Pasteurella multocida.

ANIMALS

31 healthy New Zealand White rabbits.

PROCEDURES

Steam-autoclaved stainless steel implants inoculated with P multocida underwent a second steam autoclave sterilization (AIA) or CAPS (AICAPS). One AIA implant and 3 AICAPS implants were randomly placed subcutaneously at 4 sites in 21 rabbits (84 implants). These rabbits were monitored daily for 5 days for evidence of systemic illness and local tissue reactions at the implantation sites and then euthanized. Samples were taken from each implant site for bacterial culture and histologic examination.

RESULTS

Cultures of samples obtained from all sites were negative for bacterial growth. No significant difference was observed in mean skin thickness or erythema between AIA and AICAPS implant sites on any observed day. Also, individual histologic grades for the epidermis, dermis, subcutis, and muscle and total histologic grade were not significantly different between AIA and AICAPS implant sites.

CONCLUSIONS AND CLINICAL RELEVANCE

Cold atmospheric plasma sterilization was noninferior to steam sterilization of P multocida-contaminated stainless steel implants in the rabbits in the present study. However, studies of the efficacy of CAPS for inactivation of other important bacteria are needed.

The antimicrobial and tissue healing efficacy of the atmospheric pressure cold plasma on grade III infected pressure ulcer: randomized controlled in vivo experiment

AIM

To evaluate the antimicrobial efficacy and wound healing effect of atmospheric pressure cold plasma (APCP) on an infected pressure ulcer (IPUs) model that was created on rats.

METHODS

A total of 18 rats was divided into APCP, silver sulfadiazine (AgS) and control groups to have six rats in each group. A third-grade pressure ulcer model was developed on the back of each of the rats, and pressure ulcers were infected by inoculation of multidrug resistance (MDR) Pseudomonas aeruginosa. A portable dielectric barrier discharge device was used to generate cold air plasma. APCP, AgS and saline treatments were carried out once a day for 14 days. The effectiveness of the treatment was evaluated on days 5, 10 and 15. Surface area, depth, pressure ulcer healing scale (PUSH) and microbiological examination were used for evaluation.

RESULTS

The results of this study showed that APCP was superior over AgS application and irrigation with saline by means of the reduction in surface area and depth of ulcers. Furthermore, PUSH score in plasma group was lower than other groups and histopathological examination showed a higher epithelization in APCP group. The average reductions of MDR P. aeruginosa for APCP, AgS and control groups were determined as 5·64 ± 1·87, 1·91 ± 0·90 and 1·22 ± 0·88 log10 CFU per gram tissue, respectively.

CONCLUSION

Atmospheric pressure cold plasma healed IPUs better than AgS.

SIGNIFICANCE AND IMPACT OF THE STUDY

Portable cold plasma devices could be a potential novel treatment modality for the patients who have IPUs.

A review of bacterial biofilm control by physical strategies

Biofilms are multicellular communities of microorganisms held together by a self-produced extracellular matrix, which contribute to hygiene problems in the food and medical fields. Both spoilage and pathogenic bacteria that grow in the complex structure of biofilm are more resistant to harsh environmental conditions and conventional antimicrobial agents. Therefore, it is important to develop eco-friendly preventive methodologies to eliminate biofilms from foods and food contact equipment. The present paper gives an overview of the current physical methods for biofilm control and removal. Current physical strategies adopted for the anti-biofilm treatment mainly focused on use of ultrasound power, electric or magnetic field, plasma, and irradiation. Furthermore, the mechanisms of anti-biofilm action and application of different physical methods are discussed. Physical strategies make it possible to combat biofilm without the use of biocidal agents. The remarkable microbiocidal properties of physical strategies are promising tools for antimicrobial applications.

Safety evaluation of atmospheric pressure plasma jets in in vitro and in vivo experiments

Purpose

The atmospheric pressure plasma jet (APPJ) has been introduced as an effective disinfection method for titanium surfaces due to their massive radical generation at low temperatures. Helium (He) has been widely applied as a discharge gas in APPJ due to its bactericidal effects and was proven to be effective in our previous study. This study aimed to evaluate the safety and effects of He-APPJ application at both the cell and tissue levels.

Methods

Cellular-level responses were examined using human gingival fibroblasts and osteoblasts (MC3T3-E1 cells). He-APPJ was administered to the cells in the experimental group, while the control group received only He-gas treatment. Immediate cell responses and recovery after He-APPJ treatment were examined in both cell groups. The effect of He-APPJ on osteogenic differentiation was evaluated via an alkaline phosphatase activity assay. In vivo, He-APPJ treatment was administered to rat calvarial bone and the adjacent periosteum, and samples were harvested for histological examination.

Results

He-APPJ treatment for 5 minutes induced irreversible effects in both human gingival fibroblasts and osteoblasts in vitro. Immediate cell detachment of human gingival fibroblasts and osteoblasts was shown regardless of treatment time. However, the detached areas in the groups treated for 1 or 3 minutes were completely repopulated within 7 days. Alkaline phosphatase activity was not influenced by 1 or 3 minutes of plasma treatment, but was significantly lower in the 5 minute-treated group (P=0.002). In vivo, He-APPJ treatment was administered to rat calvaria and periosteum for 1 or 3 minutes. No pathogenic changes occurred at 7 days after He-APPJ treatment in the He-APPJ-treated group compared to the control group (He gas only).

Conclusions

Direct He-APPJ treatment for up to 3 minutes showed no harmful effects at either the cell or tissue level.

The emerging potential of cold atmospheric plasma in skin biology

The maintenance of skin integrity is crucial to ensure the physiological barrier against exogenous compounds, microorganisms and dehydration but also to fulfill social and aesthetic purposes. Besides the development of new actives intended to enter a formulation, innovative technologies based on physical principles have been proposed in the last years. Among them, Cold Atmospheric Plasma (CAP) technology, which already showed interesting results in dermatology, is currently being studied for its potential in skin treatments and cares. CAP bio-medical studies gather several different expertise ranging from physics to biology through chemistry and biochemistry, making this topic hard to pin. In this review we provide a broad survey of the interactions between CAP and skin. In the first section, we tried to give some fundamentals on skin structure and physiology, related to its essential functions, together with the main bases on cold plasma and its physicochemical properties. In the following parts we dissected and analyzed each CAP parameter to highlight the already known and the possible effects they can play on skin. This overview aims to get an idea of the potential of cold atmospheric plasma technology in skin biology for the future developments of dermo-cosmetic treatments, for example in aging prevention.

Plasma medicine: Opportunities for nanotechnology in a digital age

Advances in digital technologies have opened new opportunities for creating more reliable, time- and cost-effective, safer and mobile methods of diagnosing, managing and treating diseases. A few examples of advanced nano- and digital technologies are already FDA-approved for diagnosing and treating diseases. Plasma treatment is still emerging as a new healthcare technology, but it is showing a strong potential for treatment of many diseases including cancers and antimicrobial-resistant infections, with little or no adverse side effects. Here, we argue that with the ever-increasing complex healthcare challenges facing communities, including the ongoing COVID-19 pandemic, it is critical to consider combining unique properties of emerging healthcare technologies into a single multimodal treatment modality that could lead to unprecedented healthcare benefits. In this article, we focus on the healthcare opportunities created by establishing a nexus between plasma, nano- and digital technologies. We argue that the combination of plasma, nano- and digital technologies into a single multimodal healthcare package may significantly improve patient outcomes and comfort, and reduce the economic burden on community healthcare, as well as alleviate many problems related to overcrowded healthcare systems.

An In Vitro Model of Nonattached Biofilm-Like Bacterial Aggregates Based on Magnetic Levitation

Chronic infections are associated with the formation of nonattached biofilm-like aggregates. In vitro models of surface-attached biofilms do not always accurately mimic these processes. Here, we tested a new approach to create in vitro nonattached bacterial aggregates using the principle of magnetic levitation of biological objects placed into a magnetic field gradient. Bacteria grown under magnetic levitation conditions formed nonattached aggregates that were studied with confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) and characterized quantitatively. Nonattached aggregates consisted of bacteria submerged into an extracellular matrix and demonstrated features characteristic of biofilms, such as a polymeric matrix that binds Ruby Red and Congo red dyes, a prerequisite of bacterial growth, and increased resistance to gentamicin. Three quantitative parameters were explored to characterize strain-specific potential to form nonattached aggregates: geometric sizes, relative quantities of aggregated and free-swimming bacteria, and Congo red binding. Among three tested Escherichia coli strains, one strain formed nonattached aggregates poorly, and for this strain, all three of the considered parameters were different from those of the other two strains (P < 0.05). Further, we characterized biofilm formation on plastic and agar surfaces by these strains and found that good biofilm formation ability does not necessarily indicate good nonattached aggregate formation ability, and vice versa. The model and quantitative methods can be applied for in vitro studies of nonattached aggregates and modeling bacterial behavior in chronic infections, as it is important to increase our understanding of the role that nonattached bacterial aggregates play in the pathogenesis of chronic diseases.IMPORTANCE An increasing amount of evidence indicates that chronic infections are associated with nonattached biofilm-like aggregates formed by pathogenic bacteria. These aggregates differ from biofilms because they form under low-shear conditions within the volume of biological fluids and they do not attach to surfaces. Here, we describe an in vitro model that provides nonattached aggregate formation within the liquid volume due to magnetic levitation. Using this model, we demonstrated that despite morphological and functional similarities of nonattached aggregates and biofilms, strains that exhibit good biofilm formation might exhibit poor nonattached aggregate formation, suggesting that mechanisms underlying the formation of biofilms and nonattached aggregates are not identical. The magnetic levitation approach can be useful for in vitro studies of nonattached aggregate formation and simulation of bacterial behavior in chronic infections.

Safety and bactericidal efficacy of cold atmospheric plasma generated by a flexible surface Dielectric Barrier Discharge device against Pseudomonas aeruginosa in vitro and in vivo

Background

Cold atmospheric plasma (CAP), which is ionized gas produced at atmospheric pressure, could be a novel and potent antimicrobial therapy for the treatment of infected wounds. Previously we have shown that CAP generated with a flexible surface Dielectric Barrier Discharge (sDBD) is highly effective against bacteria in vitro and in ex vivo burn wound models. In the current paper, we determined the in vitro and in vivo safety and efficacy of CAP generated by this sDBD device.

Methods

The effect of CAP on DNA mutations of V79 fibroblasts was measured using a hypoxanthine–guanine-phosphoribosyltransferase (HPRT) assay. Furthermore, effects on cell proliferation, apoptosis and DNA damage in ex vivo burn wound models (BWMs) were assessed using immunohistochemistry. Next, 10⁵ colony forming units (CFU) P. aeruginosa strain PAO1 were exposed to CAP in a 3D collagen-elastin matrix environment to determine the number of surviving bacteria in vitro. Finally, rat excision wounds were inoculated with 10⁷ CFU PAO1 for 24 h. The wounds received a single CAP treatment, repeated treatments on 4 consecutive days with CAP, 100 µL of 1% (wt/wt) silver sulfadiazine or no treatment. Wound swabs and punch biopsies were taken to determine the number of surviving bacteria.

Results

Exposure of V79 fibroblasts to CAP did not increase the numbers of mutated colonies. Additionally, the number of proliferative, apoptotic and DNA damaged cells in the BWMs was comparable to that of the unexposed control. Exposure of PAO1 to CAP for 2 min resulted in the complete elimination of bacteria in vitro. Contrarily, CAP treatment for 6 min of rat wounds colonized with PAO1 did not effectively reduce the in vivo bacterial count.

Conclusions

CAP treatment was safe but showed limited efficacy against PAO1 in our rat wound infection model.

In vitro antimicrobial effects and mechanism of air plasma‐activated water on Staphylococcus aureus biofilm

The deactivation effects and mechanism of plasma‐activated water (PAW) against Staphylococcus aureus biofilm and the inhibitory effect on the biofilm regrowth capacity for the surviving S. aureus post PAW treatment were investigated in vitro. Systematic measurements on bacterial cultivability, metabolic capacity, membrane integrity and intracellular reactive oxygen species (ROS) concentration under two different experimental categories were carried out after PAW treatment. Considerable deactivation effects were discovered on biofilm S. aureus on both prolonging the PAW inducement or treatment time. The rising concentration of intracellular ROS and the PAW‐contained RS might exert synergistic effects in deactivating the biofilm S. aureus. Moreover, the biomass, bacterial cultivability and metabolic capacity of the regrown S. aureus biofilm all significantly declined along with the increasing PAW inducement or treatment time. Therefore, except for the short‐term rapid inactivation effects on the biofilm, the PAW treatment could also exert long‐term inhibitory effects on the regeneration of S. aureus biofilm.

Functionalized biomaterials to combat biofilms

Pathogenic microbial biofilms that readily form on implantable medical devices or human tissues have posed a great threat to worldwide healthcare. Hopes are focused on preventive strategies towards biofilms, leaving a thought-provoking question: how to tackle the problem of established biofilms? In this review, we briefly summarize the functionalized biomaterials to combat biofilms and highlight current approaches to eradicate pre-existing biofilms. We believe that all of these strategies, alone or in combination, could represent a blueprint for fighting biofilm-associated infections in the postantibiotic era.

Indirect, Non-Thermal Atmospheric Plasma Promotes Bacterial Killing in vitro and Wound Disinfection in vivo Using Monogenic and Polygenic Models of Type 2 Diabetes (Without Adverse Metabolic Complications)

A novel atmospheric plasma device that uses indirect, non-thermal plasma generated from room air is being studied for its effects on wound disinfection in animal wounds of monogenic and polygenic murine models of type 2 diabetes. As a proof-of-concept report, the goal of this study was to demonstrate the efficacy and safety of the indirect non-thermal plasma (INTP) device in disinfecting polycarbonate filters established with Pseudomonas aeruginosa (PAO1) biofilms as well as wound disinfection in diabetic murine wounds. Dorsal excisional wounds in BALB/c, polygenic TALLYHO, and monogenic db/db mice established with PAO1 infection all demonstrated a 3-log colony-forming unit (CFU) reduction when subjected to a course of 20-min INTP treatments. Importantly, blood glucose and body weights in these animals were not significantly impacted by plasma treatment over the study period. Plasma safety was also analyzed via complete blood count and comprehensive metabolic panels, showing no deleterious systemic effects after 3 consecutive days of 20-min plasma applications. Therefore, the results obtained demonstrated the Pseudomonas aeruginosa isolates were highly sensitive to INTP in vitro, CFU reduction of infectious Pseudomonas in wounds of diabetic mice after INTP treatment is far superior to that of non-treated infected wounds, and the application of INTP shows no indication of toxic effects. Our results are consistent with indirect non-thermal atmospheric plasma as a promising adjunct to disinfecting wounds.

Surface Dielectric Barrier Discharge plasma: a suitable measure against fungal plant pathogens

Fungal diseases seriously affect agricultural production and the food industry. Crop protection is usually achieved by synthetic fungicides, therefore more sustainable and innovative technologies are increasingly required. The atmospheric pressure low-temperature plasma is a novel suitable measure. We report on the effect of plasma treatment on phytopathogenic fungi causing quantitative and qualitative losses of products both in the field and postharvest. We focus our attention on the in vitro direct inhibitory effect of non-contact Surface Dielectric Barrier Discharge on conidia germination of Botrytis cinerea, Monilinia fructicola, Aspergillus carbonarius and Alternaria alternata. A few minutes of treatment was required to completely inactivate the fungi on an artificial medium. Morphological analysis of spores by Scanning Electron Microscopy suggests that the main mechanism is plasma etching due to Reactive Oxygen Species or UV radiation. Spectroscopic analysis of plasma generated in humid air gives the hint that the rotational temperature of gas should not play a relevant role being very close to room temperature. In vivo experiments on artificially inoculated cherry fruits demonstrated that inactivation of fungal spores by the direct inhibitory effect of plasma extend their shelf life. Pre-treatment of fruits before inoculation improve the resistance to infections maybe by activating defense responses in plant tissues.

Antibacterial effects of low-temperature plasma generated by atmospheric-pressure plasma jet are mediated by reactive oxygen species

Emergence and spread of antibiotic resistance calls for development of non-chemical treatment options for bacterial infections. Plasma medicine applies low-temperature plasma (LTP) physics to address biomedical problems such as wound healing and tumor suppression. LTP has also been used for surface disinfection. However, there is still much to be learned regarding the effectiveness of LTP on bacteria in suspension in liquids, and especially on porous surfaces. We investigated the efficacy of LTP treatments against bacteria using an atmospheric-pressure plasma jet and show that LTP treatments have the ability to inhibit both gram-positive (S. aureus) and gram-negative (E. coli) bacteria on solid and porous surfaces. Additionally, both direct LTP treatment and plasma-activated media were effective against the bacteria suspended in liquid culture. Our data indicate that reactive oxygen species are the key mediators of the bactericidal effects of LTP and hydrogen peroxide is necessary but not sufficient for antibacterial effects. In addition, our data suggests that bacteria exposed to LTP do not develop resistance to further treatment with LTP. These findings suggest that this novel atmospheric-pressure plasma jet could be used as a potential alternative to antibiotic treatments in vivo.

Evaluation of efficacy of non-thermal atmospheric pressure plasma in treatment of periodontitis: a randomized controlled clinical trial

OBJECTIVES

In this clinical study, we aim to evaluate the effectiveness of non-thermal atmospheric pressure plasma (NAPP), which is a novel procedure used in periodontal pocket decontamination adjunctive to non-surgical periodontal treatment (NSPT).

METHODS

The study included 25 systemically healthy periodontitis patients. In the split-mouth design, NAPP application into the pockets, in addition to NSPT, was performed. Clinical periodontal data, gingival crevicular fluid, and subgingival plaque samples of patients were taken before and during the first and third months of treatment. Biochemical assays were conducted using enzyme-linked immunosorbent assay. Analysis of bacteria was performed with polymerase chain reaction method.

RESULTS

There was more clinical attachment level (CAL) gain in the 3rd month in the test group (deep pockets: 3.90 mm, pockets ≥ 5 mm: 2.72 mm) compared to the control group (deep pockets: 3.40 mm, pockets ≥ 5 mm: 2.58 mm) (p < 0.05), but no significant difference between groups in CAL. Clinical periodontal parameters improved in both study groups (p < 0.05). However, the gingival index (GI) and the bleeding on probing (BOP) rate decreased more in the test group (GI: 0.55, BOP: 9.48%, and GI: 0.38, BOP: 8.46% in the 1st and 3rd months, respectively) compared to the control group (GI: 0.68, BOP: 13.43%, and GI: 0.52, BOP: 14.58%) (p < 0.05). In addition, there was no significant difference in probing depth and biochemical markers between groups (p > 0.05). It was observed that NAPP reduced the number of bacteria more than the control group in the 1st and 3rd months.

CONCLUSIONS

It was seen that the single-time NAPP application concurrent with NSPT provided additional CAL gain, elimination of putative periodontopathogens and reduced their recolonization. Longitudinal studies with larger population and longer time are required.

CLINICAL RELEVANCE

NSPT is an effective method for the treatment of periodontitis but bacteria recolonization that causes recurrence of the periodontal disease occurs within a short period. NAPP can reduce the recurrence of periodontal disease by providing better bacterial elimination and should, therefore, be used in maintenance of periodontitis.

Potential factors contributing to the poor antimicrobial efficacy of SAAP-148 in a rat wound infection model

BACKGROUND

We investigated the efficacy of a synthetic antimicrobial peptide SAAP-148, which was shown to be effective against Methicillin-resistant Staphylococcus aureus (MRSA) on tape-stripped mice skin. Unexpectedly, SAAP-148 was not effective against MRSA in our pilot study using rats with excision wounds. Therefore, we investigated factors that might have contributed to the poor efficacy of SAAP-148. Subsequently, we optimised the protocol and assessed the efficacy of SAAP-148 in an adapted rat study.

METHODS

We incubated 100 µL of SAAP-148 with 1 cm2 of a wound dressing for 1 h and determined the unabsorbed volume of peptide solution. Furthermore, 105 colony forming units (CFU)/mL MRSA were exposed to increasing dosages of SAAP-148 in 50% (v/v) human plasma, eschar- or skin extract or PBS. After 30 min incubation, the number of viable bacteria was determined. Next, ex vivo skin models were inoculated with MRSA for 1 h and exposed to SAAP-148. Finally, excision wounds on the back of rats were inoculated with 107 CFU MRSA overnight and treated with SAAP-148 for 4 h or 24 h. Subsequently, the number of viable bacteria was determined.

RESULTS

Contrary to Cuticell, Parafilm and Tegaderm film, < 20% of peptide solution was recovered after incubation with gauze, Mepilex border and Opsite Post-op. Furthermore, in plasma, eschar- or skin extract > 20-fold higher dosages of SAAP-148 were required to achieve a 2-log reduction (LR) of MRSA versus SAAP-148 in PBS. Exposure of ex vivo models to SAAP-148 for 24 h resulted in a 4-fold lower LR than a 1 h or 4 h exposure period. Additionally, SAAP-148 caused a 1.3-fold lower mean LR at a load of 107 CFU compared to 105 CFU MRSA. Moreover, exposure of ex vivo excision wound models to SAAP-148 resulted in a 1.5-fold lower LR than for tape-stripped skin. Finally, SAAP-148 failed to reduce the bacterial counts in an adapted rat study.

CONCLUSIONS

Several factors, such as absorption of SAAP-148 by wound dressings, components within wound exudates, re-colonisation during the exposure of SAAP-148, and a high bacterial load may contribute to the poor antimicrobial effect of SAAP-148 against MRSA in the rat model.

Innovative Cold Atmospheric Plasma (iCAP) Decreases Mucopurulent Corneal Ulcer Formation and Edema and Reduces Bacterial Load in Pseudomonas Keratitis

Purpose

To evaluate the effect of application of 3% air in helium cold atmospheric plasma jet, using an inexpensive device termed iCAP, in corneal scratch wound closure in vitro and the treatment of Pseudomonas aeruginosa (P. aeruginosa) keratitis in vivo.

Methods

Thermal imaging to measure temperature of surfaces to which iCAP was applied and UV energy density delivered by iCAP were measured. Scratch wounds inflicted on in vitro cultures of a human corneal epithelial cell line were treated with iCAP and wound widths at various times post-application were measured. Rabbit eyes infected with P. aeruginosa were treated with iCAP and slit lamp biomicroscope examination conducted to determine corneal health outcomes 25h post infection. Corneal homogenates were plated on agar and viable bacterial colonies enumerated to determine the effect of iCAP on bacterial load in vivo in P. aeruginosa keratitis.

Results

iCAP was shown to operate in the non-thermal regime and also shown to deliver much lower UV energy density than that necessary to cause harmful effects on ocular tissue. iCAP treatment significantly improved the rate of scratch wound gap closure in vitro in a human corneal epithelial cell line compared to controls. In vivo, iCAP treatment of P. aeruginosa keratitis infection in the rabbit eyes (N = 20) significantly reduced the incidence of corneal ulcer (P = 0.003) and corneal edema (P = 0.011) and significantly improved total cornea health (P = 0.034) compared to untreated (N = 10). Finally, in vivo iCAP treatment of P. aeruginosa keratitis infection in the rabbit eyes (N = 19) significantly reduced bacterial loads (P = 0.012) compared to untreated (N = 9).

Conclusion

Our results strongly suggest that iCAP treatment was effective in improving corneal epithelial defect closure in vitro, reducing ulcer formation and decreasing inflammation in P. aeruginosa infected corneas in vivo and decreasing bacterial loads in P. aeruginosa infected corneas in vivo which led to improved overall cornea health outcomes in vivo. Further studies to investigate iCAP's safety and efficacy against other infectious microbes responsible for causing ulcerative keratitis, with and without co-treatment with antimicrobial therapies are warranted.

In vitro evaluation of the decontamination effect of cold atmospheric argon plasma on selected bacteria frequently encountered in small animal bite injuries

Beneficial effects of cold atmospheric argon plasma (CAAP) on wound healing and its capacity for bacterial decontamination has recently been documented. First, in vivo studies in small animals did not prove any decontamination effect in canine bite wounds. The present study evaluated the overall decontamination effect of CAAP for different bacteria frequently encountered in canine bite wounds with respect to growth phase, initial bacteria concentration and treatment duration. Standard strains of Escherichia (E.) coli, Staphylococcus (S.) pseudintermedius, S. aureus, Streptococcus (S.) canis, Pseudomonas (P.) aeruginosa and Pasteurella multocida were investigated. To evaluate the influence of the bacterial growth phase, each bacterium was incubated for three and eight hours, before CAAP treatment. Three different bacterial concentrations were created per bacterium and growth phase, and were exposed to CAAP for 30 s, 1 min and 2 min. CAAP treatment resulted in acceptable decontamination rates (range 98.9-99.9%) in all bacteria species in vitro; however, differences in susceptibility were detected. Decontamination rate was mainly influenced by initial bacterial concentration and treatment time. Growth phase only influenced decontamination in S. pseudintermedius. Treatment time significantly (P < .05) correlated with the decontamination rate in E. coli, S. canis and S. aureus, with an exposure time of 2 min being most effective. Initial bacterial concentration significantly (P < .05) influenced decontamination in Pasteurella multocida and P. aeruginosa, in which treatment time was not as important. CAAP exerts effective antibacterial activity against the tested bacteria strains in vitro, with species specific effects of treatment time, growth phase and concentration.

Singlet oxygen generated by a new nonthermal atmospheric pressure air plasma device exerts a bactericidal effect on oral pathogens

Oral diseases generally have certain bacteria associated with them. Non-thermal atmospheric pressure plasma (NTAP), generated at atmospheric pressure and room temperature, incorporates several molecules, including reactive oxygen species, that can inactivate various bacteria including oral pathogens. For this reason, several NTAP devices have been developed to treat oral diseases. Use of noble gases can enhance the bactericidal efficacy of NTAP, but this requires additional gas supply equipment. Therefore, a new NTAP device that employs ambient air as the working gas was developed. The device generates non-thermal atmospheric pressure air plasma. Here, the singlet oxygen (¹O₂) levels generated, their bactericidal effects on oral pathogens (Streptococcus mutans, Porphyromonas gingivalis, and Enterococcus faecalis), and the bacterial oxidative stress they imposed were measured. ¹O₂ generation in phosphatebuffered saline was assessed qualitatively using electron spin resonance (ESR) spectroscopy, and bactericidal efficacy was evaluated by counting of colony-forming units/mL. Bacterial oxidative stress was determined by measurement of hydrogen peroxide (H₂O₂) and superoxide dismutase (SOD) activity. ESR indicated that the level of ¹O₂ increased significantly and time-dependently, and was inversely correlated with distance, but the bactericidal effects were correlated only with treatment time (not distance) as H₂O₂ increased and SOD levels decreased, suggesting that the new device has potential applicability for treatment of oral disease.