Microscopic Droplet Size Analysis (MDSA) of "Five Thieves' Oil" (Olejek Pieciu Zlodziei) Essential Oil after the Nebulization Process.

Nowadays, due to a higher resistance to drugs, antibiotics, and antiviral medicaments, new ways of fighting pathogens are intensively studied. The alternatives for synthesized compositions are natural products, most of which have been known in natural medicine for a long time. One of the best-known and intensively investigated groups are essential oils (EOs) and their compositions. However, it is worth noting that the method of application can play a second crucial part in the effectiveness of the antimicrobial activity. EOs possess various natural compounds which exhibit antimicrobial activity. One of the compositions which is based on the five main ingredients of eucalyptus, cinnamon, clove, rosemary, and lemon is named "five thieves' oil" (Polish name: olejek pieciu zlodziei) (5TO) and is used in natural medicine. In this study, we focused on the droplet size distribution of 5TO during the nebulization process, evaluated by the microscopic droplet size analysis (MDSA) method. Furthermore, viscosity studies, as well as UV-Vis of the 5TO suspensions in medical solvents such as physiological salt and hyaluronic acid, were presented, along with measurements of refractive index, turbidity, pH, contact angle, and surface tension. Additional studies on the biological activity of 5TO solutions were made on the P. aeruginosa strain NFT3. This study opens a way for the possible use of 5TO solutions or emulsion systems for active antimicrobial applications, i.e., for surface spraying.

Synthesis, Antimicrobial, and Antibiofilm Activities of Some Novel 7-Methoxyquinoline Derivatives Bearing Sulfonamide Moiety against Urinary Tract Infection-Causing Pathogenic Microbes.

A new series of 4-((7-methoxyquinolin-4-yl) amino)-N-(substituted) benzenesulfonamide 3(a-s) was synthesized via the reaction of 4-chloro-7-methoxyquinoline 1 with various sulfa drugs. The structural elucidation was verified based on spectroscopic data analysis. All the target compounds were screened for their antimicrobial activity against Gram-positive bacteria, Gram-negative bacteria, and unicellular fungi. The results revealed that compound 3l has the highest effect on most tested bacterial and unicellular fungal strains. The highest effect of compound 3l was observed against E. coli and C. albicans with MIC = 7.812 and 31.125 µg/mL, respectively. Compounds 3c and 3d showed broad-spectrum antimicrobial activity, but the activity was lower than that of 3l. The antibiofilm activity of compound 3l was measured against different pathogenic microbes isolated from the urinary tract. Compound 3l could achieve biofilm extension at its adhesion strength. After adding 10.0 µg/mL of compound 3l, the highest percentage was 94.60% for E. coli, 91.74% for P. aeruginosa, and 98.03% for C. neoformans. Moreover, in the protein leakage assay, the quantity of cellular protein discharged from E. coli was 180.25 µg/mL after treatment with 1.0 mg/mL of compound 3l, which explains the creation of holes in the cell membrane of E. coli and proves compound 3l's antibacterial and antibiofilm properties. Additionally, in silico ADME prediction analyses of compounds 3c, 3d, and 3l revealed promising results, indicating the presence of drug-like properties.

Eco-friendly and effective antimicrobial Melaleuca alternifolia essential oil Pickering emulsions stabilized with cellulose nanofibrils against bacteria and SARS-CoV-2.

Melaleuca alternifolia essential oil (MaEO) is a green antimicrobial agent suitable for confection eco-friendly disinfectants to substitute conventional chemical disinfectants commonly formulated with toxic substances that cause dangerous environmental impacts. In this contribution, MaEO-in-water Pickering emulsions were successfully stabilized with cellulose nanofibrils (CNFs) by a simple mixing procedure. MaEO and the emulsions presented antimicrobial activities against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Moreover, MaEO deactivated the SARS-CoV-2 virions immediately. FT-Raman and FTIR spectroscopies indicate that the CNF stabilizes the MaEO droplets in water by the dipole-induced-dipole interactions and hydrogen bonds. The factorial design of experiments (DoE) indicates that CNF content and mixing time have significant effects on preventing the MaEO droplets' coalescence during 30-day shelf life. The bacteria inhibition zone assays show that the most stable emulsions showed antimicrobial activity comparable to commercial disinfectant agents such as hypochlorite. The MaEO/water stabilized-CNF emulsion is a promissory natural disinfectant with antibacterial activity against these bacteria strains, including the capability to damage the spike proteins at the SARS-CoV-2 particle surface after 15 min of direct contact when the MaEO concentration is 30 % v/v.

Bioactive metabolites of Streptomyces misakiensis display broad-spectrum antimicrobial activity against multidrug-resistant bacteria and fungi.

Background: Antimicrobial resistance is a serious threat to public health globally. It is a slower-moving pandemic than COVID-19, so we are fast running out of treatment options. Purpose: Thus, this study was designed to search for an alternative biomaterial with broad-spectrum activity for the treatment of multidrug-resistant (MDR) bacterial and fungal pathogen-related infections. Methods: We isolated Streptomyces species from soil samples and identified the most active strains with antimicrobial activity. The culture filtrates of active species were purified, and the bioactive metabolite extracts were identified by thin-layer chromatography (TLC), preparative high-performance liquid chromatography (HPLC), nuclear magnetic resonance (NMR) spectroscopy, and gas chromatography-mass spectrometry (GC-MS). The minimum inhibitory concentrations (MICs) of the bioactive metabolites against MDR bacteria and fungi were determined using the broth microdilution method. Results: Preliminary screening revealed that Streptomyces misakiensis and S. coeruleorubidus exhibited antimicrobial potential. The MIC50 and MIC90 of S. misakiensis antibacterial bioactive metabolite (ursolic acid methyl ester) and antifungal metabolite (tetradecamethylcycloheptasiloxane) against all tested bacteria and fungi were 0.5 µg/ml and 1 µg/mL, respectively, versus S. coeruleorubidus metabolites: thiocarbamic acid, N,N-dimethyl, S-1,3-diphenyl-2-butenyl ester against bacteria (MIC50: 2 µg/ml and MIC90: 4 µg/mL) and fungi (MIC50: 4 µg/ml and MIC90: 8 µg/mL). Ursolic acid methyl ester was active against ciprofloxacin-resistant strains of Streptococcus pyogenes, S. agalactiae, Escherichia coli, Klebsiella pneumoniae, and Salmonella enterica serovars, colistin-resistant Aeromonas hydrophila and K. pneumoniae, and vancomycin-resistant Staphylococcus aureus. Tetradecamethylcycloheptasiloxane was active against azole- and amphotericin B-resistant Candida albicans, Cryptococcus neoformans, C. gattii, Aspergillus flavus, A. niger, and A. fumigatus. Ursolic acid methyl ester was applied in vivo for treating S. aureus septicemia and K. pneumoniae pneumonia models in mice. In the septicemia model, the ursolic acid methyl ester-treated group had a significant 4.00 and 3.98 log CFU/g decrease (P < 0.05) in liver and spleen tissue compared to the infected, untreated control group. Lung tissue in the pneumonia model showed a 2.20 log CFU/g significant decrease in the ursolic acid methyl ester-treated group in comparison to the control group. The haematological and biochemical markers in the ursolic acid methyl ester-treated group did not change in a statistically significant way. Moreover, no abnormalities were found in the histopathology of the liver, kidneys, lungs, and spleen of ursolic acid methyl ester-treated mice in comparison with the control group. Conclusion: S. misakiensis metabolite extracts are broad-spectrum antimicrobial biomaterials that can be further investigated for the potential against MDR pathogen infections. Hence, it opens up new horizons for exploring alternative drugs for current and reemerging diseases.

Synthetic and natural guanidine derivatives as antitumor and antimicrobial agents: A review.

Guanidines are fascinating small nitrogen-rich organic compounds, which have been frequently associated with a wide range of biological activities. This is mainly due to their interesting chemical features. For these reasons, for the past decades, researchers have been synthesizing and evaluating guanidine derivatives. In fact, there are currently on the market several guanidine-bearing drugs. Given the broad panoply of pharmacological activities displayed by guanidine compounds, in this review, we chose to focus on antitumor, antibacterial, antiviral, antifungal, and antiprotozoal activities presented by several natural and synthetic guanidine derivatives, which are undergoing preclinical and clinical studies from January 2010 to January 2023. Moreover, we also present guanidine-containing drugs currently in the market for the treatment of cancer and several infectious diseases. In the preclinical and clinical setting, most of the synthesized and natural guanidine derivatives are being evaluated as antitumor and antibacterial agents. Even though DNA is the most known target of this type of compounds, their cytotoxicity also involves several other different mechanisms, such as interference with bacterial cell membranes, reactive oxygen species (ROS) formation, mitochondrial-mediated apoptosis, mediated-Rac1 inhibition, among others. As for the compounds already used as pharmacological drugs, their main application is in the treatment of different types of cancer, such as breast, lung, prostate, and leukemia. Guanidine-containing drugs are also being used for the treatment of bacterial, antiprotozoal, antiviral infections and, recently, have been proposed for the treatment of COVID-19. To conclude, the guanidine group is a privileged scaffold in drug design. Its remarkable cytotoxic activities, especially in the field of oncology, still make it suitable for a deeper investigation to afford more efficient and target-specific drugs.

Iron Acquisition and Metabolism as a Promising Target for Antimicrobials (Bottlenecks and Opportunities): Where Do We Stand?

The emergence of multidrug-resistant (MDR) and extensively drug-resistant (XDR) infections is one of the most crucial challenges currently faced by the scientific community. Developments in the fundamental understanding of their underlying mechanisms may open new perspectives in drug discovery. In this review, we conducted a systematic literature search in PubMed, Web of Science, and Scopus, to collect information on innovative strategies to hinder iron acquisition in bacteria. In detail, we discussed the most interesting targets from iron uptake and metabolism pathways, and examined the main chemical entities that exhibit anti-infective activities by interfering with their function. The mechanism of action of each drug candidate was also reviewed, together with its pharmacodynamic, pharmacokinetic, and toxicological properties. The comprehensive knowledge of such an impactful area of research will hopefully reflect in the discovery of newer antibiotics able to effectively tackle the antimicrobial resistance issue.

A review on antimicrobial mechanism and applications of graphene-based materials.

In recent years, graphene and its derivatives, owing to their phenomenal surface, and mechanical, electrical, and chemical properties, have emerged as advantageous materials, especially in terms of their potential for antimicrobial applications. Particularly important among graphene's derivatives is graphene oxide (GO) due to the ease with which its surface can be modified, as well as the oxidative and membrane stress that it exerts on microbes. This review encapsulates all aspects regarding the functionalization of graphene-based materials (GBMs) into composites that are highly potent against bacterial, viral, and fungal activities. Governing factors, such as lateral size (LS), number of graphene layers, solvent and GBMs' concentration, microbial shape and size, aggregation ability of GBMs, and especially the mechanisms of interaction between composites and microbes are discussed in detail. The current and potential applications of these antimicrobial materials, especially in dentistry, osseointegration, and food packaging, have been described. This knowledge can further drive research that aims to look for the most suitable components for antimicrobial composites. The need for antimicrobial materials has seldom been more felt than during the COVID-19 pandemic, which has also been highlighted here. Possible future research areas include the exploration of GBMs' ability against algae.

A Natural Virucidal and Microbicidal Spray Based on Polyphenol-Iron Sols.

Numerous disinfection methods have been developed to reduce the transmission of infectious diseases that threaten human health. However, it still remains elusively challenging to develop eco-friendly and cost-effective methods that deactivate a wide range of pathogens, from viruses to bacteria and fungi, without doing any harm to humans or the environment. Herein we report a natural spraying protocol, based on a water-dispersible supramolecular sol of nature-derived tannic acid (TA) and Fe3+, which is easy-to-use and low-cost. Our formulation effectively deactivates viruses (influenza A viruses, SARS-CoV-2, and human rhinovirus) as well as suppressing the growth and spread of pathogenic bacteria (Escherichia coli, Salmonella typhimurium, Staphylococcus aureus, and Acinetobacter baumannii) and fungi (Pleurotus ostreatus and Trichophyton rubrum). Its versatile applicability in a real-life setting is also demonstrated against microorganisms present on the surfaces of common household items (e.g., air filter membranes, disposable face masks, kitchen sinks, mobile phones, refrigerators, and toilet seats).

Residual antimicrobial coating efficacy against SARS-CoV-2.

AIMS: This study evaluated the residual efficacy of commercially available antimicrobial coatings or films against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on non-porous surfaces. METHODS AND RESULTS: Products were applied to stainless steel or ABS plastic coupons and dried overnight. Coupons were inoculated with SARS-CoV-2 in the presence of 5% soil load. Recovered infectious SARS-CoV-2 was quantified by TCID50 assay. Tested product efficacies ranged from <1.0 to >3.0 log10 reduction at a 2-h contact time. The log10 reduction in recovered infectious SARS-CoV-2 ranged from 0.44 to 3 log10 reduction on stainless steel and 0.25 to >1.67 log10 on ABS plastic. The most effective products tested contained varying concentrations (0.5%-1.3%) of the same active ingredient: 3-(trihydroxysilyl) propyldimethyloctadecyl ammonium chloride. Products formulated with other quaternary ammonium compounds were less effective against SARS-CoV-2 in this test. CONCLUSIONS: The residual antimicrobial products tested showed varied effectiveness against SARS-CoV-2 as a function of product tested. Several products were identified as efficacious against SARS-CoV-2 on both stainless steel and ABS plastic surfaces under the conditions evaluated. Differences in observed efficacy may be due to variation in active ingredient formulation; efficacy is, therefore, difficult to predict based upon listed active ingredient and its concentration. SIGNIFICANCE AND IMPACT: This study highlights the formulation-specific efficacy of several products against SARS-CoV-2 and may inform future development of residual antiviral products for use on non-porous surfaces. The identification of antimicrobial coatings or films showing promise to inactivate SARS-CoV-2 suggests that these products may be worth future testing and consideration.

One-Step Synthesis of Self-Stratification Core-Shell Latex for Antimicrobial Coating.

Herein, we describe a one-step method for synthesizing cationic acrylate-based core-shell latex (CACS latex), which is used to prepare architectural coatings with excellent antimicrobial properties. Firstly, a polymerizable water-soluble quaternary ammonium salt (QAS-BN) was synthesized using 2-(Dimethylamine) ethyl methacrylate (DMAEMA) and benzyl bromide by the Hoffman alkylation reaction. Then QAS-BN, butyl acrylate (BA), methyl methacrylate (MMA), and vinyltriethoxysilane (VTES) as reactants and 2,2'-azobis(2-methylpropionamidine) dihydrochloride (AIBA) as a water-soluble initiator were used to synthesize the CACS latex. The effect of the QAS-BN dosage on the properties of the emulsion and latex film was systematically investigated. The TGA results showed that using QAS-BN reduced the latex film's initial degradation temperature but improved its thermal stability. In the transmission electron microscopy (TEM) photographs, the self-stratification of latex particles with a high dosage of QAS-BN was observed, forming a core-shell structure of latex particles. The DSC, TGA, XPS, SEM, and performance tests confirmed the core-shell structure of the latex particles. The relationship between the formation of the core-shell structure and the content of QAS-BN was proved. The formation of the core-shell structure was due to the preferential reaction of water-soluble monomers in the aqueous phase, which led to the aggregation of hydrophilic groups, resulting in the formation of soft-core and hard-shell latex particles. However, the water resistance of the films formed by CACS latex was greatly reduced. We introduced a p-chloromethyl styrene and n-hexane diamine (p-CMS/EDA) crosslinking system, effectively improving the water resistance in this study. Finally, the antimicrobial coating was prepared with a CACS emulsion of 7 wt.% QAS-BN and 2 wt.% p-CMS/EDA. The antibacterial activity rates of this antimicrobial coating against E. coli and S. aureus were 99.99%. The antiviral activity rates against H3N2, HCoV-229E, and EV71 were 99.4%, 99.2%, and 97.9%, respectively. This study provides a novel idea for the morphological design of latex particles. A new architectural coating with broad-spectrum antimicrobial properties was obtained, which has important public health and safety applications.

Antimicrobial Performance of Innovative Functionalized Surfaces Based on Enamel Coatings: The Effect of Silver-Based Additives on the Antibacterial and Antifungal Activity.

Frequently touched surfaces (FTS) that are contaminated with pathogens are one of the main sources of nosocomial infections, which commonly include hospital-acquired and healthcare-associated infections (HAIs). HAIs are considered the most common adverse event that has a significant burden on the public's health worldwide currently. The persistence of pathogens on contaminated surfaces and the transmission of multi-drug resistant (MDR) pathogens by way of healthcare surfaces, which are frequently touched by healthcare workers, visitors, and patients increase the risk of acquiring infectious agents in hospital environments. Moreover, not only in hospitals but also in high-traffic public places, FTS play a major role in the spreading of pathogens. Consequently, attention has been devoted to developing novel and alternative methods to tackle this problem. This study planned to produce and characterize innovative functionalized enameled coated surfaces supplemented with 1% AgNO3 and 2% AgNO3. Thus, the antimicrobial properties of the enamels against relevant nosocomial pathogens including the Gram-positive Staphylococcus aureus and the Gram-negative Escherichia coli and the yeast Candida albicans were assessed using the ISO:22196:2011 norm.

Betaine- and L-Carnitine-Based Ionic Liquids as Solubilising and Stabilising Agents for the Formulation of Antimicrobial Eye Drops Containing Diacerein.

The therapeutic efficacy of topically administered drugs, however powerful, is largely affected by their bioavailability and, thus, ultimately, on their aqueous solubility and stability. The aim of this study was to evaluate the use of ionic liquids (ILs) as functional excipients to solubilise, stabilise, and prolong the ocular residence time of diacerein (DIA) in eye drop formulations. DIA is a poorly soluble and unstable anthraquinone prodrug, rapidly hydrolysed to rhein (Rhe), for the treatment of osteoarthritis. DIA has recently been evaluated as an antimicrobial agent for bacterial keratitis. Two ILs based on natural zwitterionic compounds were investigated: L-carnitine C6 alkyl ester bromide (Carn6), and betaine C6 alkyl ester bromide (Bet6). The stabilising, solubilising, and mucoadhesive properties of ILs were investigated, as well as their cytotoxicity to the murine fibroblast BALB/3T3 clone A31 cell line. Two IL-DIA-based eye drop formulations were prepared, and their efficacy against both Staphylococcus aureus and Pseudomonas aeruginosa was determined. Finally, the eye drops were administered in vivo on New Zealand albino rabbits, testing their tolerability as well as their elimination and degradation kinetics. Both Bet6 and Carn6 have good potential as functional excipients, showing solubilising, stabilising, mucoadhesive, and antimicrobial properties; their in vitro cytotoxicity and in vivo ocular tolerability pave the way for their future use in ophthalmic applications.

Biogenic nanosilver-fabricated endotracheal tube to prevent microbial colonization in a veterinary hospital.

COVID-19 patients have often required prolonged endotracheal intubation, increasing the risk of developing ventilator-associated pneumonia (VAP). A preventive strategy is proposed based on an endotracheal tube (ETT) modified by the in situ deposition of eucalyptus-mediated synthesized silver nanoparticles (AgNPs). The surfaces of the modified ETT were embedded with AgNPs of approximately 28 nm and presented a nanoscale roughness. Energy dispersive X-ray spectroscopy confirmed the presence of silver on and inside the coated ETT, which exhibited excellent antimicrobial activity against Gram-positive and Gram-negative bacteria, and fungi, including multidrug-resistant clinical isolates. Inhibition of planktonic growth and microbial adhesion ranged from 99 to 99.999% without cytotoxic effects on mammalian cells. Kinetic studies showed that microbial adhesion to the coated surface was inhibited within 2 h. Cell viability in biofilms supplemented with human tracheal mucus was reduced by up to 95%. In a porcine VAP model, the AgNPs-coated ETT prevented adhesion of Pseudomonas aeruginosa and completely inhibited bacterial invasion of lung tissue. The potential antimicrobial efficacy and safety of the coated ETT were established in a randomized control trial involving 47 veterinary patients. The microbial burden was significantly lower on the surface of the AgNPs-coated ETT than on the uncoated ETT (p < 0.05). KEY POINTS: • Endotracheal tube surfaces were modified by coating with green-synthesized AgNPs • P. aeruginosa burden of endotracheal tube and lung was reduced in a porcine model • Effective antimicrobial activity and safety was demonstrated in a clinical trial.

Porous Cellulose Thin Films as Sustainable and Effective Antimicrobial Surface Coatings.

In the present work, we developed an effective antimicrobial surface film based on sustainable microfibrillated cellulose. The resulting porous cellulose thin film is barely noticeable to human eyes due to its submicrometer thickness, of which the surface coverage, porosity, and microstructure can be modulated by the formulations and the coating process. Using goniometers and a quartz crystal microbalance, we observed a threefold reduction in water contact angles and accelerated water evaporation kinetics on the cellulose film (more than 50% faster than that on a flat glass surface). The porous cellulose film exhibits a rapid inactivation effect against SARS-CoV-2 in 5 min, following deposition of virus-loaded droplets, and an exceptional ability to reduce contact transfer of liquid, e.g., respiratory droplets, to surfaces such as an artificial skin by 90% less than that from a planar glass substrate. It also shows excellent antimicrobial performance in inhibiting the growth of both Gram-negative and Gram-positive bacteria (Escherichia coli and Staphylococcus epidermidis) due to the intrinsic porosity and hydrophilicity. Additionally, the cellulose film shows nearly 100% resistance to scraping in dry conditions due to its strong affinity to the supporting substrate but with good removability once wetted with water, suggesting its practical suitability for daily use. Importantly, the coating can be formed on solid substrates readily by spraying, which requires solely a simple formulation of a plant-based cellulose material with no chemical additives, rendering it a scalable, affordable, and green solution as antimicrobial surface coating. Implementing such cellulose films could thus play a significant role in controlling future pan- and epidemics, particularly during the initial phase when suitable medical intervention needs to be developed and deployed.

Artificial intelligence-based optimization for chitosan nanoparticles biosynthesis, characterization and in­vitro assessment of its anti-biofilm potentiality.

Chitosan nanoparticles (CNPs) are promising biopolymeric nanoparticles with excellent physicochemical, antimicrobial, and biological properties. CNPs have a wide range of applications due to their unique characteristics, including plant growth promotion and protection, drug delivery, antimicrobials, and encapsulation. The current study describes an alternative, biologically-based strategy for CNPs biosynthesis using Olea europaea leaves extract. Face centered central composite design (FCCCD), with 50 experiments was used for optimization of CNPs biosynthesis. The artificial neural network (ANN) was employed for analyzing, validating, and predicting CNPs biosynthesis using Olea europaea leaves extract. Using the desirability function, the optimum conditions for maximum CNPs biosynthesis were determined theoretically and verified experimentally. The highest experimental yield of CNPs (21.15 mg CNPs/mL) was obtained using chitosan solution of 1%, leaves extract solution of 100%, initial pH 4.47, and incubation time of 60 min at 53.83°C. The SEM and TEM images revealed that CNPs had a spherical form and varied in size between 6.91 and 11.14 nm. X-ray diffraction demonstrates the crystalline nature of CNPs. The surface of the CNPs is positively charged, having a Zeta potential of 33.1 mV. FTIR analysis revealed various functional groups including C-H, C-O, CONH2, NH2, C-OH and C-O-C. The thermogravimetric investigation indicated that CNPs are thermally stable. The CNPs were able to suppress biofilm formation by P. aeruginosa, S. aureus and C. albicans at concentrations ranging from 10 to 1500 µg/mL in a dose-dependent manner. Inhibition of biofilm formation was associated with suppression of metabolic activity, protein/exopolysaccharide moieties, and hydrophobicity of biofilm encased cells (r ˃ 0.9, P = 0.00). Due to their small size, in the range of 6.91 to 11.14 nm, CNPs produced using Olea europaea leaves extract are promising for applications in the medical and pharmaceutical industries, in addition to their potential application in controlling multidrug-resistant microorganisms, especially those associated with post COVID-19 pneumonia in immunosuppressed patients.

Hierarchical Superstructure of Plant Polyphenol and Arginine Surfactant for Long-Lasting and Target-Selective Antimicrobial Application.

Antimicrobial agents are massively used to disinfect the pathogen contaminated surfaces since the Corona Virus Disease 2019 (COVID-19) outbreak. However, their defects of poor durability, strong irritation, and high environmental accumulation are exposed. Herein, a convenient strategy is developed to fabricate long-lasting and target-selective antimicrobial agent with the special hierarchical structure through bottom-up assembly of natural gallic acid with arginine surfactant. The assembly starts from rodlike micelles, further stacking into hexagonal columns and finally interpenetrating into spherical assemblies, which avoid explosive release of antimicrobial units. The assemblies show anti-water washing and high adhesion on various surfaces; and thus, possess highly efficient and broad-spectrum antimicrobial activities even after using up to eleven cycles. Both in vitro and in vivo experiments prove that the assemblies are highly selective in killing pathogens without generating toxicity. The excellent antimicrobial virtues well satisfy the increasing anti-infection demands and the hierarchical assembly exhibits great potential as a clinical candidate.

Laboratory Evaluation of a Quaternary Ammonium Compound-Based Antimicrobial Coating Used in Public Transport during the COVID-19 Pandemic.

The virucidal activity of the Zoono Z71 Microbe Shield surface sanitizer and protectant, a quaternary ammonium compound (QAC)-based antimicrobial coating that was used by the United Kingdom rail industry during the COVID-19 pandemic, was evaluated, using the bacteriophage ɸ6 as a surrogate for SARS-CoV-2. Immediately after application and in the absence of interfering substances, the product effectively reduced (>3 log10) the viability of ɸ6 on some materials that are typically used in rail carriages (stainless steel, high-pressure laminate, plastic). If, after the application of the product, these surfaces remained undisturbed, the antimicrobial coating retained its efficacy for at least 28 days. However, efficacy depended on the material being coated. The product provided inconsistent results when applied to glass surfaces and was ineffective (i.e., achieved <3 log10 reduction) when applied to a train arm rest that was made of Terluran 22. Regardless of the material that was coated or the time since application, the presence of organic debris (fetal bovine serum) significantly reduced the viricidal activity of the coating. Wiping the surface with a wetted cloth after the deposition of organic debris was not sufficient to restore efficacy. We conclude that the product is likely to be of limited effectiveness in a busy, multiuser environment, such as public transport. IMPORTANCE This study evaluated the performance of a commercially available antimicrobial coating that was used by the transport industry in the United Kingdom during the COVID-19 pandemic. While the product was effective against ɸ6, the efficacy of the coating depended upon the material to which it was applied. Similarly, and regardless of the surface material, the presence of organic debris severely impaired viricidal activity, and efficacy could not be recovered through wiping (cleaning) the surface. This highlights the importance of including relevant materials and conditions when evaluating antimicrobial coatings in the laboratory. Further efforts are required to identify suitable infection prevention and control practices for the transport industry.

Drug Repositioning as a Therapeutic Strategy against Streptococcus pneumoniae: Cell Membrane as Potential Target.

A collection of repurposing drugs (Prestwick Chemical Library) containing 1200 compounds was screened to investigate the drugs' antimicrobial effects against planktonic cultures of the respiratory pathogen Streptococcus pneumoniae. After four discrimination rounds, a set of seven compounds was finally selected, namely (i) clofilium tosylate; (ii) vanoxerine; (iii) mitoxantrone dihydrochloride; (iv) amiodarone hydrochloride; (v) tamoxifen citrate; (vi) terfenadine; and (vii) clomiphene citrate (Z, E). These molecules arrested pneumococcal growth in a liquid medium and induced a decrease in bacterial viability between 90.0% and 99.9% at 25 µM concentration, with minimal inhibitory concentrations (MICs) also in the micromolar range. Moreover, all compounds but mitoxantrone caused a remarkable increase in the permeability of the bacterial membrane and share a common, minimal chemical structure consisting of an aliphatic amine linked to a phenyl moiety via a short carbon/oxygen linker. These results open new possibilities to tackle pneumococcal disease through drug repositioning and provide clues for the design of novel membrane-targeted antimicrobials with a related chemical structure.

Antimicrobial betalains.

Betalains are nitrogen-containing plant pigments that can be red-violet (betacyanins) or yellow-orange (betaxanthins), currently employed as natural colourants in the food and cosmetic sectors. Betalains exhibit antimicrobial activity against a broad spectrum of microbes including multidrug-resistant bacteria, as well as single-species and dual-species biofilm-producing bacteria, which is highly significant given the current antimicrobial resistance issue reported by The World Health Organization. Research demonstrating antiviral activity against dengue virus, in silico studies including SARS-CoV-2, and anti-fungal effects of betalains highlight the diversity of their antimicrobial properties. Though limited in vivo studies have been conducted, antimalarial and anti-infective activities of betacyanin have been observed in living infection models. Cellular mechanisms of antimicrobial activity of betalains are yet unknown; however existing research has laid the framework for a potentially novel antimicrobial agent. This review covers an overview of betalains as antimicrobial agents and discussions to fully exploit their potential as therapeutic agents to treat infectious diseases.

Antiviral Peptides in Antimicrobial Surface Coatings-From Current Techniques to Potential Applications.

The transmission of pathogens through contact with contaminated surfaces is an important route for the spread of infections. The recent outbreak of COVID-19 highlights the necessity to attenuate surface-mediated transmission. Currently, the disinfection and sanitization of surfaces are commonly performed in this regard. However, there are some disadvantages associated with these practices, including the development of antibiotic resistance, viral mutation, etc.; hence, a better strategy is necessary. In recent years, peptides have been studied to be utilized as a potential alternative. They are part of the host immune defense and have many potential in vivo applications in drug delivery, diagnostics, immunomodulation, etc. Additionally, the ability of peptides to interact with different molecules and membrane surfaces of microorganisms has made it possible to exploit them in ex vivo applications such as antimicrobial (antibacterial and antiviral) coatings. Although antibacterial peptide coatings have been studied extensively and proven to be effective, antiviral coatings are a more recent development. Therefore, this study aims to highlight antiviral coating strategies and the current practices and application of antiviral coating materials in personal protective equipment, healthcare devices, and textiles and surfaces in public settings. Here, we have presented a review on potential techniques to incorporate peptides in current surface coating strategies that will serve as a guide for developing cost-effective, sustainable and coherent antiviral surface coatings. We further our discussion to highlight some challenges of using peptides as a surface coating material and to examine future perspectives.