Copper and quaternary ammonium cations exert synergistic bactericidal and antibiofilm activity against Pseudomonas aeruginosa

Antibacterial Activity of Brass against Antibiotic-Resistant Bacteria following Repeated Exposure to Hydrogen Peroxide/Peracetic Acid and Quaternary Ammonium Compounds

Copper-containing materials are attracting attention as self-disinfecting surfaces, suitable for helping healthcare settings in reducing healthcare-associated infections. However, the impact of repeated exposure to disinfectants frequently used in biocleaning protocols on their antibacterial activity remains insufficiently characterized. This study aimed at evaluating the antibacterial efficiency of copper (positive control), a brass alloy (AB+®) and stainless steel (negative control) after repeated exposure to a quaternary ammonium compound and/or a mix of peracetic acid/hydrogen peroxide routinely used in healthcare settings. A panel of six antibiotic-resistant strains (clinical isolates) was selected for this assessment. After a short (5 min) exposure time, the copper and brass materials retained significantly better antibacterial efficiencies than stainless steel, regardless of the bacterial strain or disinfectant treatment considered. Moreover, post treatment with both disinfectant products, copper-containing materials still reached similar levels of antibacterial efficiency to those obtained before treatment. Antibiotic resistance mechanisms such as efflux pump overexpression did not impair the antibacterial efficiency of copper-containing materials, nor did the presence of one or several genes related to copper homeostasis/resistance. In light of these results, surfaces made out of copper and brass remain interesting tools in the fight against the dissemination of antibiotic-resistant strains that might cause healthcare-associated infections.

Synergistic antibacterial effect and mechanism between Cu2O nanoparticles and quaternary ammonium salt in moisture-curable acrylic coatings

Combining with various antibacterial mechanisms is the preferred strategy to fabricate coatings with effective antibacterial performance. Herein, Cu2O nanoparticles and dimethyloctadecyl [3-(trimethoxysilyl) propyl] ammonium chloride, a kind of quaternary ammonium salt (QAS), were simultaneously incorporated into a moisture-curable acrylic resin in order to achieve both contact-killing and release-killing abilities for antibacterial coatings. The surface morphology, surface composition and basic properties of the coatings were thoroughly characterized. The antibacterial performance of the coatings was determined by in-vitro bacteriostatic test. Under the constant total mass fraction of antibacterial agents, both Cu2O and QAS content possessed the highest value on the coating surface at Cu2O/QAS mass ratio of 1:1, and correspondingly, the coatings reached sterilizing rate above 99 % against both E. coli and S. loihica, indicating the existence of synergistic effect between Cu2O and QAS. The synergistic antibacterial mechanism of the coatings involved two aspects. Firstly, the combination of contact-killing and release-killing biocides resulted in high bactericidal and antibiofilm activity against different bacteria. Further, the grafting of QAS molecules on the surface of Cu2O particles brought about the spontaneous migration of nanoparticles to the coating surface. The interaction between Cu2O and QAS also inhibited the phase separation of QAS and prolonged the release of Cu2+ at the same time. The coatings, therefore, exhibited stable antibacterial performance at varied service conditions.

Navigating Antibacterial Frontiers: A Panoramic Exploration of Antibacterial Landscapes, Resistance Mechanisms, and Emerging Therapeutic Strategies

The development of effective antibacterial solutions has become paramount in maintaining global health in this era of increasing bacterial threats and rampant antibiotic resistance. Traditional antibiotics have played a significant role in combating bacterial infections throughout history. However, the emergence of novel resistant strains necessitates constant innovation in antibacterial research. We have analyzed the data on antibacterials from the CAS Content Collection, the largest human-curated collection of published scientific knowledge, which has proven valuable for quantitative analysis of global scientific knowledge. Our analysis focuses on mining the CAS Content Collection data for recent publications (since 2012). This article aims to explore the intricate landscape of antibacterial research while reviewing the advancement from traditional antibiotics to novel and emerging antibacterial strategies. By delving into the resistance mechanisms, this paper highlights the need to find alternate strategies to address the growing concern.

Antibacterial efficacy of copper-based metal-organic frameworks against Escherichia coli and Lactobacillus

The widespread and excessive use of antimicrobial drugs has resulted in a concerning rise in bacterial resistance, leading to a risk of untreatable infections. The aim of this study was to formulate a robust and efficient antibacterial treatment to address this challenge. Previous work focused on the effectiveness of the Cu-BTC metal-organic framework (MOF; BTC stands for 1,3,5-benzenetricarboxylate) in combatting various bacterial strains. Herein, we compare the antibacterial properties of Cu-BTC with our newly designed Cu-GA MOF, consisting of copper ions bridged by deprotonated gallate ligands (H2gal2-), against Escherichia coli (E. coli) and Lactobacillus bacteria. Cu-GA was synthesized hydrothermally from copper salt and naturally derived gallic acid (H4gal) and characterized for antibacterial evaluation. The gradual breakdown of Cu(H2gal) resulted in a significant antibacterial effect that is due to the release of copper ions and gallate ligands from the framework. Both copper MOFs were nontoxic to bacteria at low concentrations and growth was completely inhibited at high concentrations when treated with Cu-BTC (1500 μg for E. coli and 1700 μg for Lactobacillus) and Cu-GA (2000 μg for both bacterial strains). Furthermore, our agarose gel electrophoresis results indicate that both MOFs could disrupt bacterial cell membranes, hindering the synthesis of DNA. These findings confirm the antibacterial properties of Cu-BTC and the successful internalization of Cu2+ ions and gallic acid by bacteria from the Cu-GA MOF framework, suggesting the potential for a sustained and effective therapeutic approach against pathogenic microorganisms.

A microtiter peg lid with ziggurat geometry for medium-throughput antibiotic testing and in situ imaging of biofilms

Bacteria biofilm responses to disinfectants and antibiotics are quantified and observed using multiple methods, though microscopy, particularly confocal laser scanning microscopy (CLSM) is preferred due to speed, a reduction in user error, and in situ analysis. CLSM can resolve biological and spatial heterogeneity of biofilms in 3D with limited throughput. The microplate peg-lid-based assay, described in ASTM E2799-22, is a medium-throughput method for testing biofilms but does not permit in situ imaging. Breaking off the peg, as recommended by the manufacturer, risks sample damage, and is limited to easily accessible pegs. Here we report modifications to the peg optimized for in situ visualization and visualization of all pegs. We report similar antibiotic challenge recovery via colony formation following the ASTM E2799-22 protocol and in situ imaging. We report novel quantifiable effects of antibiotics on biofilm morphologies, specifically biofilm streamers. The new design bridges the MBEC® assays design that selects for biofilm phenotypes with in situ imaging needs.

Synergistic Promotion System of Montmorillonite with Cu2+ and Benzalkonium Chloride for Efficient and Broad-Spectrum Antibacterial Activity

By intercalating montmorillonite (MMT) with Cu2+ and benzalkonium chloride (BAC), the present work constructed a synergistic promotion system (Cu2+/BAC/MMT). MMT not only enhances the thermal stability of Cu2+ and BAC but also facilitates the controlled release of Cu2+ and BAC. Concurrently, the introduction of BAC improves the material's organic compatibility. In vitro assays show that the "MIC+" of Cu2+/BAC/MMT against Staphylococcus aureus is merely 7.32 mg/L and 55.56 mg/L against Escherichia coli. At concentrations of 10 and 25 mg/L, Cu2+/BAC/MMT inactivates 100% of S. aureus and E. coli within 2 h, respectively. Furthermore, it is confirmed that the prepared Cu2+/BAC/MMT exhibits a long-term antibacterial ability through antibacterial experiments and release tests. Also, the biosafety of this material was also substantiated by in vitro cytotoxicity tests. These comprehensive findings indisputably portend that Cu2+/BAC/MMT holds promise to supplant antibiotics as an efficacious treatment modality for bacterial infections.

Insights into the Synergistic Antibacterial Activity of Silver Nitrate with Potassium Tellurite against Pseudomonas aeruginosa

The constant, ever-increasing antibiotic resistance crisis leads to the announcement of "urgent, novel antibiotics needed" by the World Health Organization. Our previous works showed a promising synergistic antibacterial activity of silver nitrate with potassium tellurite out of thousands of other metal/metalloid-based antibacterial combinations. The silver-tellurite combined treatment not only is more effective than common antibiotics but also prevents bacterial recovery, decreases the risk of future resistance chance, and decreases the effective concentrations. We demonstrate that the silver-tellurite combination is effective against clinical isolates. Further, this study was conducted to address knowledge gaps in the available data on the antibacterial mechanism of both silver and tellurite, as well as to give insight into how the mixture provides synergism as a combination. Here, we defined the differentially expressed gene profile of Pseudomonas aeruginosa under silver, tellurite, and silver-tellurite combination stress using an RNA sequencing approach to examine the global transcriptional changes in the challenged cultures grown in simulated wound fluid. The study was complemented with metabolomics and biochemistry assays. Both metal ions mainly affected four cellular processes, including sulfur homeostasis, reactive oxygen species response, energy pathways, and the bacterial cell membrane (for silver). Using a Caenorhabditis elegans animal model we showed silver-tellurite has reduced toxicity over individual metal/metalloid salts and provides increased antioxidant properties to the host. This work demonstrates that the addition of tellurite would improve the efficacy of silver in biomedical applications. IMPORTANCE Metals and/or metalloids could represent antimicrobial alternatives for industrial and clinical applications (e.g., surface coatings, livestock, and topical infection control) because of their great properties, such as good stability and long half-life. Silver is the most common antimicrobial metal, but resistance prevalence is high, and it can be toxic to the host above a certain concentration. We found that a silver-tellurite composition has antibacterial synergistic effect and that the combination is beneficial to the host. So, the efficacy and application of silver could increase by adding tellurite in the recommended concentration(s). We used different methods to evaluate the mechanism for how this combination can be so incredibly synergistic, leading to efficacy against antibiotic- and silver-resistant isolates. Our two main findings are that (i) both silver and tellurite mostly target the same pathways and (ii) the coapplication of silver with tellurite tends not to target new pathways but targets the same pathways with an amplified change.

Structure based virtual screening and molecular dynamics of natural anti-biofilm compounds against SagS response regulator/sensor kinase in Pseudomonas aeruginosa

SagS sensor regulator plays a vital role in biofilm development of Pseudomonas aeruginosa which subsequently makes the cells more tolerant to various antimicrobials. The multidrug resistance (MDR) issue has risen substantially in recent years and is considered a global threat. Therefore, alternative compounds should be unearthed immediately to address the issues related to P. aeruginosa drug resistance for which SagS could be a candidate. The present study is an attempt to screen natural anti-biofilm compounds as the potent inhibitors of SagS. Twenty natural anti-biofilm/quorum sensing inhibiting compounds were retrieved from various literatures with significant inhibitory effects against P. aeruginosa biofilm from in-vitro experiments which were screened using various pharmacokinetic parameters. The screened and three standard drugs were docked against SagS-HisKA using AutoDock 4.2 tool, which were further analysed by MD simulations to understand the binding mode of compounds and dynamic behaviour of the complexes. Two potential anti-biofilm natural compounds, pinocembrin with binding affinity (-7.19 kcal/mol), vestitol (-7.18 kcal/mol) and the standard drug ceftazidime (-8.89 kcal/mol) were selected based on filtered parameters and better binding affinity. The trajectory analysis of MD simulations reflected Pinocembrin in stabilizing the system compared to ceftazidime. The existing reports state that the natural products represent promising source of therapy with least or almost nil adverse effect compared to synthetic drugs which is well collated with our in-silico findings. This investigation can save both time and cost required for in-vitro and in-vivo analysis for designing of a novel anti-biofilm agent against P. aeruginosa biofilm-associated infections.Communicated by Ramaswamy H. Sarma.

Antibacterial and antibiofilm efficacy of the preferred fractions and compounds from Euphorbia humifusa (herba euphorbiae humifusae) against Staphylococcus aureus

ETHNOPHARMACOLOGICAL RELEVANCE

Euphorbia humifusa Willd., known as Di-Jin-Cao in Chinese, has long been utilized as a traditional herb for the treatment of furuncles and carbuncles mainly caused by Staphylococcus aureus infection. Despite extensive chemical and pharmacological studies reported previously for E. humifusa, the antibacterial and antibiofilm activities against S. aureus as well as the related mechanism of action (MoA) remain largely obscure.

AIM OF THE STUDY

To investigate the antibacterial and antibiofilm activities of the preferred fractions and compounds from E. humifusa against S. aureus and assess the associated MoA.

MATERIALS AND METHODS

The bioactive fractions and compounds were obtained from the 75% ethanol extract of E. humifusa (75%-EEEH) with the assistance of the related antibacterial and antibiofilm screening. Their antibacterial activities were determined using the broth microdilution method, whilst the inhibition of biofilm formation and the disruption of preformed biofilm were assessed by crystal violet staining and confocal laser scanning microscopy (CLSM). To achieve more effective therapies, the combinatory effects of different components were also studied. The biofilm metabolic activities of isolated compounds were evaluated by 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) reduction assay. The scanning electron microscopy (SEM) and quantitative real-time polymerase chain reaction (qRT-PCR) were employed to explore the antibiofilm mechanism.

RESULTS

Fractions DJC06 and DJC07 collected from the ethyl acetate extract of the 75%-EEEH exhibited antibacterial activity (MIC = 256 μg/mL) against S. aureus and further separation of these two fractions led to the isolation and characterization of 22 compounds. Among the isolates, luteolin (LU), quercetin (QU), and kaempferol (KA) are the verified components associated with the antibacterial and antibiofilm activities by displaying individual or combinational MIC values of 8-128 μg/mL and 70.9-99.7% inhibition for biofilm formation. Importantly, QU and KA can work in synergy with LU to significantly enhance the efficacy via destroying cell integrity, increasing membrane permeability, and down-regulating the biofilm-related gene expression.

CONCLUSIONS

The preferred fractions and compounds from E. humifusa exerted desired antibacterial and antibiofilm efficacy against S. aureus via a MoA involving cell morphology disruption and altered genes expression. The findings herein not only support its traditional use in the treatment of furuncles and carbuncles, but reveal E. humifusa is a potential source for producing promising antibiofilm alternatives against S. aureus and highlight the isolated components (LU, QU, KA) that can potentiate the efficacy when used in synergy.

Synthesis, characterization, and antibacterial activities of a heteroscorpionate derivative platinum complex against methicillin-resistant Staphylococcus aureus

Staphylococcus aureus is one of the species with the greatest clinical importance and greatest impact on public health. In fact, methicillin-resistant S. aureus (MRSA) is considered a pandemic pathogen, being essential to develop effective medicines and combat its rapid spread. This study aimed to foster the translation of clinical research outcomes based on metallodrugs into clinical practice for the treatment of MRSA. Bearing in mind the promising anti-Gram-positive effect of the heteroscorpionate ligand 1,1’-(2-(4-isopropylphenyl)ethane-1,1-diyl)bis(3,5-dimethyl-1H-pyrazole) (2P), we propose the coordination of this compound to platinum as a clinical strategy with the ultimate aim of overcoming resistance in the treatment of MRSA. Therefore, the novel metallodrug 2P-Pt were synthetized, fully characterized and its antibacterial effect against the planktonic and biofilm state of S. aureus evaluated. In this sense, three different strains of S. aureus were studied, one collection strain of S. aureus sensitive to methicillin and two clinical MRSA strains. To appraise the antibacterial activity, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), minimum biofilm inhibitory concentration (MBIC), and minimum biofilm eradication concentration (MBEC) were determined. Moreover, successful outcomes on the development of biofilm in a wound-like medium were obtained. The mechanism of action for 2P-Pt was proposed by measuring the MIC and MBC with EDTA (cation mediated mechanism) and DMSO (exogenous oxidative stress mechanism). Moreover, to shed light on the plausible antistaphylococcal mechanism of this novel platinum agent, additional experiments using transmission electron microscopy were carried out. 2P-Pt inhibited the growth and eradicated the three strains evaluated in the planktonic state. Another point worth stressing is the inhibition in the growth of MRSA biofilm even in a wounded medium. The results of this work support this novel agent as a promising therapeutic alternative for preventing infections caused by MRSA.

Preparation, antioxidant and antibacterial activities of cryptate copper(II)/sulfonate chitosan complexes

In this work, we synthesized cryptate copper(II) followed by complexed with sulfonate chitosan (SCS). After characterization, the evaluation of the antioxidant properties of resulting complexes were carried out by 1,1-Diphenyl-2-picrylhydrazyl radical (DPPH•), hydroxyl radical (•OH), and 2,2'-Azinobis-(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS^•+), while the antibacterial and biofilm inhibitory activity against Pseudomonas aeruginosa PAO1 (P. aeruginosa PAO1) were also investigated. According to the results, cryptate copper(II) exhibited the best antioxidant activity followed by cryptate copper(II)/SCS complexes, and SCS. Significant antibacterial activity of cryptate copper(II) against P. aeruginosa PAO1 was observed with the minimum inhibitory concentration of MIC value 12.50 μg/mL and minimum bactericidal concentration of MBC value 100.00 μg/mL, followed by cryptate copper(II)/SCS complexes and SCS. Cryptate copper(II) and cryptate copper(II)/SCS exhibited antibacterial activity which copper ions might enter the interior of cells, and the intracellular ions made the killed bacteria serve as an antibacterial agent showing a zombie effect. The copper ions complexed with cryptate and SCS rendering potential unlimited biological activities, might become one of the most popular research areas because of their unique coordination chemistry and their long-term biological activities.

Design and Synthesis of 3-Hydroxy-pyridin-4(1H)-ones-Ciprofloxacin Conjugates as Dual Antibacterial and Antibiofilm Agents against Pseudomonas aeruginosa

Pseudomonas aeruginosa infections are often complicated by the fact that it can easily form a biofilm that increases its resistance to antibiotics. Consequently, the development of novel antibacterial agents against biofilm-associated drug-resistant P. aeruginosa is urgently needed. Herein, we report a series of 3-hydroxy-pyridin-4(1H)-ones-ciprofloxacin conjugates that were designed and synthesized as dual antibacterial and antibiofilm agents against P. aeruginosa. A potential 2-substituted 3-hydroxy-1,6-dimethylpyridin-4(1H)-one-ciprofloxacin conjugate (5e) was identified and had the best minimum inhibitory concentrations of 0.86 and 0.43 μM against P. aeruginosa 27853 and PAO1 and reduced 78.3% of biofilm formation. In addition, 5e eradicates mature biofilms and kills living bacterial cells that are incorporated into the biofilm. Studies on the antibiofilm mechanism of conjugates showed that 5e interferes with iron uptake by bacteria, inhibits their motility, and reduces the production of virulence. These results demonstrate that 3-hydroxy-pyridin-4(1H)-ones-ciprofloxacin conjugates are potent in the treatment of biofilm-associated drug-resistant P. aeruginosa infections.

Comparison of Antimicrobial and Antibiofilm Activity of Proflavine Co-crystallized with Silver, Copper, Zinc, and Gallium Salts

Here, we exploit our mechanochemical synthesis for co-crystallization of an organic antiseptic, proflavine, with metal-based antimicrobials (silver, copper, zinc, and gallium). Our previous studies have looked for general antimicrobial activity for the co-crystals: proflavine·AgNO3, proflavine·CuCl, ZnCl3[Proflavinium], [Proflavinium]2[ZnCl4]·H2O, and [Proflavinium]3[Ga(oxalate)3]·4H2O. Here, we explore and compare more precisely the bacteriostatic (minimal inhibitory concentrations) and antibiofilm (prevention of cell attachment and propagation) activities of the co-crystals. For this, we choose three prominent "ESKAPE" bacterial pathogens of Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus. The antimicrobial behavior of the co-crystals was compared to that of the separate components of the polycrystalline samples to ascertain whether the proflavine-metal complex association in the solid state provided effective antimicrobial performance. We were particularly interested to see if the co-crystals were effective in preventing bacteria from initiating and propagating the biofilm mode of growth, as this growth form provides high antimicrobial resistance properties. We found that for the planktonic lifestyle of growth of the three bacterial strains, different co-crystal formulations gave selectivity for best performance. For the biofilm state of growth, we see that the silver proflavine co-crystal has the best overall antibiofilm activity against all three organisms. However, other proflavine-metal co-crystals also show practical antimicrobial efficacy against E. coli and S. aureus. While not all proflavine-metal co-crystals demonstrated enhanced antimicrobial efficacy over their constituents alone, all possessed acceptable antimicrobial properties while trapped in the co-crystal form. We also demonstrate that the metal-proflavine crystals retain antimicrobial activity in storage. This work defines that co-crystallization of metal compounds and organic antimicrobials has a potential role in the quest for antimicrobials/antiseptics in the defense against bacteria in our antimicrobial resistance era.

Topical Antibiofilm Agents With Potential Utility in the Treatment of Chronic Rhinosinusitis: A Narrative Review

The role of bacterial biofilms in chronic and recalcitrant diseases is widely appreciated, and the treatment of biofilm infection is an increasingly important area of research. Chronic rhinosinusitis (CRS) is a complex disease associated with sinonasal dysbiosis and the presence of bacterial biofilms. While most biofilm-related diseases are associated with highly persistent but relatively less severe inflammation, the presence of biofilms in CRS is associated with greater severity of inflammation and recalcitrance despite appropriate treatment. Oral antibiotics are commonly used to treat CRS but they are often ineffective, due to poor penetration of the sinonasal mucosa and the inherently antibiotic resistant nature of bacteria in biofilms. Topical non-antibiotic antibiofilm agents may prove more effective, but few such agents are available for sinonasal application. We review compounds with antibiofilm activity that may be useful for treating biofilm-associated CRS, including halogen-based compounds, quaternary ammonium compounds and derivatives, biguanides, antimicrobial peptides, chelating agents and natural products. These include preparations that are currently available and those still in development. For each compound, antibiofilm efficacy, mechanism of action, and toxicity as it relates to sinonasal application are summarised. We highlight the antibiofilm agents that we believe hold the greatest promise for the treatment of biofilm-associated CRS in order to inform future research on the management of this difficult condition.

Antibacterial and Antibiofilm Activities of Chlorogenic Acid Against Yersinia enterocolitica

Nowadays, developing new and natural compounds with antibacterial activities from plants has become a promising approach to solve antibiotic resistance of pathogenic bacteria. Chlorogenic acid (CA), as a kind of phenolic acid existing in many plants, has been found to process multifunctional activities including antibacterial activity. Herein, the antibacterial and antibiofilm activities of CA against Yersinia enterocolitica (Y. enterocolitica) were tested for the first time, and its mechanism of action was investigated. It was demonstrated that CA could exert outstanding antibacterial activity against Y. enterocolitica. Biofilm susceptibility assays further indicated that CA could inhibit biofilm formation and decrease the established biofilm biomass of Y. enterocolitica. It was deduced that through binding to Y. enterocolitica, CA destroyed the cell membrane, increased the membrane permeability, and led to bacterial cell damage. In addition, the transcriptomic analysis revealed that CA could disorder many physiological pathways, mainly including the ones of antagonizing biofilms and increasing cell membrane permeability. Finally, the spiked assay showed that the growth of Y. enterocolitica in milk was significantly inhibited by CA. Taken together, CA, as an effective bactericidal effector with application potential, exerts antagonistic activity against Y. enterocolitica by mainly intervening biofilm formation and membrane permeability-related physiological pathways.

Phytobeneficial traits of rhizobacteria under the control of multiple molecular dialogues

Pseudomonads play crucial roles in plant growth promotion and control of plant diseases. However, under natural conditions, other microorganisms competing for the same nutrient resources in the rhizosphere may exert negative control over their phytobeneficial characteristics. We assessed the expression of phytobeneficial genes involved in biocontrol, biostimulation and iron regulation such as, phlD, hcnA, acdS, and iron‐small regulatory RNAs prrF1 and prrF2 in Pseudomonas brassicacearum co‐cultivated with three phytopathogenic fungi, and two rhizobacteria in the presence or absence of Brassica napus, and in relation to iron availability. We found that the antifungal activity of P. brassicacearum depends mostly on the production of DAPG and not on HCN whose production is suppressed by fungi. We have also shown that the two‐competing bacterial strains modulate the plant growth promotion activity of P. brassicacearum by modifying the expression of phlD, hcnA and acdS according to iron availability. Overall, it allows us to better understand the complexity of the multiple molecular dialogues that take place underground between microorganisms and between plants and its rhizosphere microbiota and to show that synergy in favour of phytobeneficial gene expression may exist between different bacterial species.

We assessed the expression of phytobeneficial genes, phlD, hcnA and acdS, and iron‐small regulatory RNAs prrF1 and prrF2 in Pseudomonas brassicacearum co‐cultivated with three phytopathogenic fungi, and two rhizobacteria in the presence or absence of Brassica napus, and in relation to iron availability. Our study illustrates that interkingdom and interspecies interactions in addition to external factors may affect the success of introduced beneficial microorganisms by modulating the expression of phytobeneficial genes.

Synergistic Antimicrobial Metal Oxide-Doped Phosphate Glasses; a Potential Strategy to Reduce Antimicrobial Resistance and Host Cell Toxicity

The emergence of antimicrobial resistant strains bacteria and a decline in the discovery of new antibiotics has led to the idea of combining various antimicrobials to treat resistant strains and/or polymicrobial infections. Metal oxide-doped glasses have been extensively investigated for their antimicrobial potential; however to date, most experiments have focused on single metal species in isolation. The present study investigates the antimicrobial potential of sodium calcium phosphates (P₂O₅)₅₀(Na₂O)₂₀(CaO)_30-X(MO)_X, where M is cobalt, copper, or zinc as single species. In addition, this work studied the effect of co-doping glasses containing two different metal ions (Co + Cu, Co + Zn, and Cu + Zn). The antimicrobial efficacy of all glasses was tested against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacterial strains, as well as a fungal strain (Candida albicans). Minimum inhibitory and bactericidal concentrations and time kill/synergy assays were used to assess the antimicrobial activity. An enhanced antimicrobial effect, at 5 mg/mL concentration, was exhibited by cobalt, copper, and zinc oxide glasses alone and in combinations. A synergistic antimicrobial effect was observed by Cu + Co and Cu + Zn against E. coli and Cu + Zn against S. aureus.

Advancement of Gallium and Gallium-Based Compounds as Antimicrobial Agents

With the abuse and misuse of antibiotics, antimicrobial resistance has become a challenging issue in the medical system. Iatrogenic and non-iatrogenic infections caused by multidrug-resistant (MDR) pathogens pose serious threats to global human life and health because the efficacy of traditional antibiotics has been greatly reduced and the resulting socio-economic burden has increased. It is important to find and develop non-antibiotic-dependent antibacterial strategies because the development of new antibiotics can hardly keep pace with the emergence of resistant bacteria. Gallium (III) is a multi-target antibacterial agent that has an excellent antibacterial activity, especially against MDR pathogens; thus, a gallium (III)-based treatment is expected to become a new antibacterial strategy. However, some limitations of gallium ions as antimicrobials still exist, including low bioavailability and explosive release. In recent years, with the development of nanomaterials and clathrates, the progress of manufacturing technology, and the emergence of synergistic antibacterial strategies, the antibacterial activities of gallium have greatly improved, and the scope of application in medical systems has expanded. This review summarizes the advancement of current optimization for these key factors. This review will enrich the knowledge about the efficiency and mechanism of various gallium-based antibacterial agents and provide strategies for the improvement of the antibacterial activity of gallium-based compounds.

Selective Anticancer and Antimicrobial Metallodrugs Based on Gold(III) Dithiocarbamate Complexes

New dithiocarbamate cycloaurated complexes have been synthesized and their physicochemical and in vitro antitumor properties have been evaluated. All the performed studies highlighted good transport through the blood and biodistribution, according to the balance between the properties of hydrophilicity/lipophilicity and the binding of moderate strength to the BSA protein. Furthermore, none of the complexes exhibited reduction or decomposition reactions, presenting excellent physiological stability. The in vitro cytotoxic effect was evaluated on human colon cancer cell line Caco-2/TC7, and the complexes showed great antiproliferative activity and excellent selectivity, as much less effect was detected on normal Caco-2/TC7 cells. Most of the complexes exhibit antiproliferative activity that was better than or similar to auranofin, and at least nine times better than that of cisplatin. Its action mechanism is still under discussion since no evidence of cell cycle arrest was found, but an antioxidant role was shown for some of the selective complexes. All complexes were also tested as antimicrobial drugs, exhibiting good activity towards S. aureus and E. coli. bacteria and C. albicans and C. neoformans fungi.

In Vitro Effect of Copper (I) Complex [Cu(NN1)2](ClO4) on Vibrio harveyi BB170 Biofilm Formation

Biofilm formation in pathogenic bacteria is an important factor of resistance to antimicrobial treatments, allowing them to survive for a long time in their hosts. In the search for new antibiofilm agents, in this work we report the activity of a copper (I) complex, [Cu(NN₁)₂]ClO₄, synthesized with Cu (I) and NN1, an imine ligand 6-((quinolin-2-ylmethylene)amino)-2H-chromen-2-one, a derivate of natural compound coumarin. The antibacterial and antibiofilm capacity was evaluated in Vibrio harveyi BB170 used as model bacteria. Antibacterial activity was measured in vitro by minimal inhibitory concentration (MIC), minimal bactericidal concentration (MBC) and half-maximal inhibitory concentration (IC₅₀) determination. Antibiofilm capacity of copper (I) complex was analyzed by different concentrations of IC₅₀ values. The results showed that the sub-IC₅₀ concentration, 12.6 µg/mL of the copper (I) complex, was able to reduce biofilm formation by more than 75%, and bacterial viability was reduced by 50%. Inverted and confocal laser scanning microscopy showed that the [Cu(NN₁)₂]ClO₄ complex affected the biofilm structure. Therefore, the copper (I) complex is effective as an antibiofilm compound in V. harveyi BB170.

The Mutation in wbaP cps Gene Cluster Selected by Phage-Borne Depolymerase Abolishes Capsule Production and Diminishes the Virulence of Klebsiella pneumoniae

Klebsiella pneumoniae is considered one of the most critical multidrug-resistant pathogens and urgently requires new therapeutic strategies. Capsular polysaccharides (CPS), lipopolysaccharides (LPS), and exopolysaccharides (EPS) are the major virulence factors protecting K. pneumoniae against the immune response and thus may be targeted by phage-based therapeutics such as polysaccharides-degrading enzymes. Since the emergence of resistance to antibacterials is generally considered undesirable, in this study, the genetic and phenotypic characteristics of resistance to the phage-borne CPS-degrading depolymerase and its effect on K. pneumoniae virulence were investigated. The K63 serotype targeting depolymerase (KP36gp50) derived from Klebsiella siphovirus KP36 was used as the selective agent during the treatment of K. pneumoniae 486 biofilm. Genome-driven examination combined with the surface polysaccharide structural analysis of resistant mutant showed the point mutation and frameshift in the wbaP gene located within the cps gene cluster, resulting in the loss of the capsule. The sharp decline in the yield of CPS was accompanied by the production of a larger amount of smooth LPS. The modification of the surface polysaccharide layers did not affect bacterial fitness nor the insensitivity to serum complement; however, it made bacteria more prone to phagocytosis combined with the higher adherence and internalization to human lung epithelial cells. In that context, it was showed that the emerging resistance to the antivirulence agent (phage-borne capsule depolymerase) results in beneficial consequences, i.e., the sensitization to the innate immune response.

Antimicrobial and Anticorrosion Activity of a Novel Composite Biocide against Mixed Bacterial Strains in Taiwanese Marine Environments

Taiwan is an island with a humid subtropical climate. The relatively warm seawater results in biofouling of the surfaces of marine facilities. Biocide application is a common practice for combating and eliminating adhesive fouling. However, a single type of biocide may have limited antimicrobial effects due to the relatively high microbial diversity in marine environments. Therefore, applying a mixture of various biocides may be necessary. In this study, the antimicrobial and anticorrosion properties of a newly designed composite biocide, namely a combination of thymol and benzyldimethyldodecylammonium chloride, were investigated by applying the biocide to 304 stainless steel substrates immersed in inocula containing bacterial strains from Tamsui and Zuoying harbors. The ability of 3TB and 5TB treatments to prevent sessile cells and biofilm formation on the 304 stainless steel coupon surface was determined through scanning electron microscopy investigation. In addition, confocal laser scanning microscopy indicated that the 5TB treatment achieved a greater bactericidal effect in both the Tamsui and Zuoying inocula. Moreover, electrochemical impedance spectroscopy revealed that the diameter of the Nyquist semicircle was almost completely unaffected by Tamsui or Zuoying under the 5TB treatment. Through these assessments of antimicrobial activity and corrosion resistance, 5TB treatment was demonstrated to have superior bactericidal activity against mixed strains in both southern and northern Taiwanese marine environments.

In Vitro Antimicrobial Susceptibility Testing of Biofilm-Growing Bacteria: Current and Emerging Methods

The antibiotic susceptibility of bacterial pathogens is typically determined based on planktonic cells, as recommended by several international guidelines. However, most of chronic infections - such as those established in wounds, cystic fibrosis lung, and onto indwelling devices - are associated to the formation of biofilms, communities of clustered bacteria attached onto a surface, abiotic or biotic, and embedded in an extracellular matrix produced by the bacteria and complexed with molecules from the host. Sessile microorganisms show significantly increased tolerance/resistance to antibiotics compared with planktonic counterparts. Consequently, antibiotic concentrations used in standard antimicrobial susceptibility tests, although effective against planktonic bacteria in vitro, are not predictive of the concentrations required to eradicate biofilm-related infections, thus leading to treatment failure, chronicization and removal of material in patients with indwelling medical devices.Meeting the need for the in vitro evaluation of biofilm susceptibility to antibiotics, here we reviewed several methods proposed in literature highlighting their advantages and limitations to guide scientists towards an appropriate choice.

Antibacterial and Antibiofilm Formation Activities of Pyridinium-Based Cationic Pillar[5]arene Against Pseudomonas aeruginosa

An omnipresent pathogenic bacterium, Pseudomonas aeruginosa (P. aeruginosa PAO1), is easy to contaminate environmental water or foods, causing daily food spoilage and infections. The biofilm-forming ability and bacterial resistance of P. aeruginosa PAO1 make it difficult to be eradicated by traditional bacteriostatic agents. In this work, we designed and synthesized a pyridinium-based pillar[5]arene (PP5), while trimethylammonium-based pillar[5]arene (TP5) was used as a control compound. After clear characterization, the antibacterial and antibiofilm activities as well as the microbial resistance of TP5 and PP5 against P. aeruginosa PAO1 were extensively examined. It was revealed that PP5 exhibited good inhibition activity with the minimum inhibitory concentration (MIC) of 0.051 mmol/L, while no significant antibacterial and biofilm formation activity for TP5 against P. aeruginosa PAO1 was observed. More importantly, PP5 had negligible antimicrobial resistance even after 18th passages. A transmission electron microscope (TEM) showed that PP5 could physically disrupt the cell membranes, causing the leakage of internal constituents, which is possibly ascribed to the synergistic penetrability and π-π interactions of strain, thus greatly reduced the development of bacterial resistance. Overall, the presented studies indicated that pyridinium moieties could facilitate the cationic pillar[5]arene to generate surprising antibacterial and antibiofilm formation ability against P. aeruginosa PAO1.

Comparative in vitro study on the local tolerance and efficacy of benzalkonium chloride, myristalkonium chloride and nonoxynol-9 as active principles in vaginal contraceptives

BACKGROUND

Spermicides have been identified as a potentially attractive alternative to hormonal contraceptives and/or intrauterine devices. Thus, this study aimed evaluating the efficacy and local tolerance of benzalkonium chloride (BKC) and myristalkonium chloride (MKC) contained in Pharmatex^® vaginal formulations and compare them with nonoxynol-9 (N-9), the most common active ingredient in topical vaginal contraceptives.

METHODS

Human normozoospermic samples were assessed for motility, viability, acrosome status and penetration ability after exposure to control, N-9 or different BKC and MKC doses for 0 and 10 minutes. Local tolerance on HeLa cells was evaluated by the Trypan-blue and MTT assays.

RESULTS

Exposure to BKC and MKC reduced acrosome integrity while promoting total immobilisation and complete loss of sperm viability (p < .001, n = 15). Both compounds also compromised sperm penetration ability upon exposure (p < .001, n = 15). N-9 induced the same outcomes (p < .001, n = 15); nevertheless, it was more toxic to HeLa cells than BKC and MKC (p < .05, n = 14).

CONCLUSIONS

BKC and MKC present strong in vitro spermicidal activity at lower doses than N-9 and were better tolerated after immediate exposure than N-9. Available Pharmatex^® galenic formulations were as effective as products based on N-9.

The evolutionary trade-offs in phage-resistant Klebsiella pneumoniae entail cross-phage sensitization and loss of multidrug resistance

Bacteriophage therapy is currently being evaluated as a critical complement to traditional antibiotic treatment. However, the emergence of phage resistance is perceived as a major hurdle to the sustainable implementation of this antimicrobial strategy. By combining comprehensive genomics and microbiological assessment, we show that the receptor-modification resistance to capsule-targeting phages involves either escape mutation(s) in the capsule biosynthesis cluster or qualitative changes in exopolysaccharides, converting clones to mucoid variants. These variants introduce cross-resistance to phages specific to the same receptor yet sensitize to phages utilizing alternative ones. The loss/modification of capsule, the main Klebsiella pneumoniae virulence factor, did not dramatically impact population fitness, nor the ability to protect bacteria against the innate immune response. Nevertheless, the introduction of phage drives bacteria to expel multidrug resistance clusters, as observed by the large deletion in K. pneumoniae 77 plasmid containing bla_CTX-M , ant(3″), sul2, folA, mph(E)/mph(G) genes. The emerging bacterial resistance to viral infection steers evolution towards desired population attributes and highlights the synergistic potential for combined antibiotic-phage therapy against K. pneumoniae.

Antibacterial and Antiviral Functional Materials: Chemistry and Biological Activity toward Tackling COVID-19-like Pandemics

The ongoing worldwide pandemic due to COVID-19 has created awareness toward ensuring best practices to avoid the spread of microorganisms. In this regard, the research on creating a surface which destroys or inhibits the adherence of microbial/viral entities has gained renewed interest. Although many research reports are available on the antibacterial materials or coatings, there is a relatively small amount of data available on the use of antiviral materials. However, with more research geared toward this area, new information is being added to the literature every day. The combination of antibacterial and antiviral chemical entities represents a potentially path-breaking intervention to mitigate the spread of disease-causing agents. In this review, we have surveyed antibacterial and antiviral materials of various classes such as small-molecule organics, synthetic and biodegradable polymers, silver, TiO2, and copper-derived chemicals. The surface protection mechanisms of the materials against the pathogen colonies are discussed in detail, which highlights the key differences that could determine the parameters that would govern the future development of advanced antibacterial and antiviral materials and surfaces.

Biofilm-specific uptake of a 4-pyridone-based iron chelator by Pseudomonas aeruginosa

Iron is an essential nutrient for virtually all microbes and limiting the concentration of available iron is a potential strategy to be used as an alternative to antibiotic treatment. In this study we analysed the antimicrobial activity of two chelators, specifically 3-hydroxy-1,2-dimethyl-4(1H)-pyridone (deferiprone, DFP), which is clinically approved for the treatment of iron overload disorders, and its 1,2-diethyl homologue, CP94. Both compounds showed moderate activity towards planktonically growing P. aeruginosa cells, and the mechanism of action of these chelators was indeed by limiting the amount of free iron. Surprisingly, the compounds behaved very differently when the cells were grown in biofilms. DFP also showed inhibitory effects on biofilm formation but in contrast, CP94 stimulated this process, in particular at high concentrations. We hypothesised that CP94 behaves as an iron carrier, which was confirmed by our observation that it had antimicrobial synergy with the toxic metals, gallium and copper. This suggests that P. aeruginosa produces a biofilm-specific transport protein that recognises CP94 but not the closely related compound DFP.

Anti-biofouling microfiltration membranes based on 1-vinyl-3-butylimidazolium chloride grafted PVDF with improved bactericidal properties and vitro biocompatibility

Polyvinylidene fluoride (PVDF) porous membranes have been widely used as the filtration and separation industry. Herein, novel microfiltration membranes based on 1-vinyl-3-butylimidazolium chloride ([VBIm][Cl]) grafted PVDF (PVDF-g-[VBIm][Cl]) were prepared via the non-solvent induced phase separation method. The chemical composition and microstructure of PVDF-g-[VBIm][Cl] membranes were characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, Scanning electron microscopy and Water contact angle measurements. The results showed that an increasing in [VBIm][Cl] grafting content leads to the increasing hydrophilicity and wetting capacity of the PVDF-g-[VBIm][Cl] porous membranes. The anti-biofouling properties of membranes were evaluated by measuring the water flux before and after Bovine serum albumin solution treatment. It was found that the modified membranes presented a good anti-biofouling property. The degree of irreversible flux loss caused by protein adsorption dramatically reduced from 42.1% to 2.9% compared with the pristine hydrophobic PVDF membranes. Meanwhile, these PVDF-g-[VBIm][Cl] membranes also exhibited excellent bactericidal properties against both gram-positive bacteria Staphylococcus saureus and gram-negative bacteria Escherichia coli, while PVDF membranes did not show any antibacterial activity. The vitro biocompatibility of the modified membranes was studied by hemolysis analysis, the platelet adhesion observation, thromboelastography assay and cytotoxicity assay. It was found that the incorporation of [VBIm][Cl] into PVDF membranes has less effect on the hemolysis and cytotoxicity of PVDF membranes. Furthermore, both hydrophilicity and charges of the membrane surface played important role in the adhesion and activation of platelet cells, which consequently affected the clotting process of whole blood. The membrane with appropriate [VBIm][Cl] grafting ratio (2.94 wt.%) exhibited good hemocompatibility with less blood coagulation effect. As an ultrafiltration membrane, PVDF-g-[VBIm][Cl] membranes have potential applications in the biomedical field due to the improved antibacterial property and biocompatibility.

Inactivation of RNA and DNA viruses in water by copper and silver ions and their synergistic effect

Cu and Ag have been used as bactericidal agents since ancient times, yet their antiviral capacity in water remains poorly understood. This study tested the effect of copper (Cu) and silver (Ag) on model RNA and DNA viruses MS2 and PhiX 174 in solution at pH 6-8. Cu caused MS2 inactivation with similar rates at pH 6 and 7 but was inert towards PhiX 174 regardless of pH. Ag inactivated both viruses, causing denaturation of MS2 and loss of capsid spikes in PhiX 174. Ag inactivation rates were pH dependent and increased with increasing pH. At pH 8, 6.5 logs of PhiX were inactivated after 3 h and 3 logs of MS2 after only 10 min. The combined use of Cu and Ag revealed synergy in disinfecting MS2 at pH ≥ 7. Although metal concentrations used were higher than the desired values for drinking water treatment, the results prove a promising potential of Cu and Ag combinations as efficient viricidal agents.

Silver Antibacterial Synergism Activities with Eight Other Metal(loid)-Based Antimicrobials against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus

The present study surveys potential antibacterial synergism effects of silver nitrate with eight other metal or metalloid-based antimicrobials (MBAs), including silver nitrate, copper (II) sulfate, gallium (III) nitrate, nickel sulfate, hydrogen tetrachloroaurate (III) trihydrate (gold), aluminum sulfate, sodium selenite, potassium tellurite, and zinc sulfate. Bacteriostatic and bactericidal susceptibility testing explored antibacterial synergism potency of 5760 combinations of MBAs against three bacteria (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus) in three different media. Silver nitrate in combination with potassium tellurite, zinc sulfate, and tetrachloroaurate trihydrate had remarkable bactericidal and bacteriostatic synergism effects. Synergism properties of MBAs decreased effective antibacterial concentrations remarkably and bacterial cell count decreased by 8.72 log10 colony-forming units (CFU)/mL in E. coli, 9.8 log10 CFU/mL in S. aureus, and 12.3 log10 CFU/mL in P. aeruginosa, compared to each MBA alone. Furthermore, most of the MBA combinations inhibited the recovery of bacteria; for instance, the combination of silver nitrate–tetrachloroaurate against P. aeruginosa inhibited the recovery of bacteria, while three-fold higher concentration of silver nitrate and two-fold higher concentration of tetrachloroaurate were required for inhibition of recovery when used individually. Overall, higher synergism was typically obtained in simulated wound fluid (SWF) rather than laboratory media. Unexpectedly, the combination of A silver nitrate–potassium tellurite had antagonistic bacteriostatic effects in Luria broth (LB) media for all three strains, while the combination of silver nitrate–potassium tellurite had the highest bacteriostatic and bactericidal synergism in SWF. Here, we identify the most effective antibacterial MBAs formulated against each of the Gram-positive and Gram-negative pathogen indicator strains.

Therapeutic Strategies To Counteract Antibiotic Resistance in MRSA Biofilm-Associated Infections

Methicillin-resistant Staphylococcus aureus (MRSA) has emerged as one of the leading causes of persistent human infections. This pathogen is widespread and is able to colonize asymptomatically about a third of the population, causing moderate to severe infections. It is currently considered the most common cause of nosocomial infections and one of the main causes of death in hospitalized patients. Due to its high morbidity and mortality rate and its ability to resist most antibiotics on the market, it has been termed a "superbug". Its ability to form biofilms on biotic and abiotic surfaces seems to be the primarily means of MRSA antibiotic resistance and pervasiveness. Importantly, more than 80 % of bacterial infections are biofilm-mediated. Biofilm formation on indwelling catheters, prosthetic devices and implants is recognized as the cause of serious chronic infections in hospital environments. In this review we discuss the most relevant literature of the last five years concerning the development of synthetic small molecules able to inhibit biofilm formation or to eradicate or disperse pre-formed biofilms in the fight against MRSA diseases. The aim is to provide guidelines for the development of new anti-virulence strategies based on the knowledge so far acquired, and, to identify the main flaws of this research field, which have hindered the generation of new market-approved anti-MRSA drugs that are able to act against biofilm-associated infections.

Micro-structured copper and nickel metal foams for wastewater disinfection: proof-of-concept and scale-up

It is necessary to disinfect treated wastewater prior to discharge to reduce exposure risks to humans and the environment. The currently practiced wastewater disinfection technologies are challenged by toxic by-products, chemicals and energy demand, a range of effectiveness limitations, among other concerns. An effective, eco-friendly, and energy-efficient alternative disinfection technique is desirable to modernize and enhance wastewater treatment operations. Copper and nickel micro-structured metal foams, and a conventional copper mesh, were evaluated as disinfecting surfaces for treating secondary-treated wastewater contaminated with coliform bacteria. The micro-structured copper foam was adopted for scale-up study, due to its stable and satisfactory bactericidal performance obtained over a wide range of bacterial concentrations and metal-to-liquid ratios. Three scales of experiments, using two types of reactor designs, were performed using municipal wastewater to determine the optimal scale-up factors: small lab-scale batch reactor, intermediate lab-scale batch reactor, and pilot-scale continuous tubular reactor experiments. The performance was evaluated with the aim of minimizing metal material requirement with respect to bactericidal efficiency and leaching risks at all scales. Copper foam, at or above optimal conditions, consistently inactivated over 95 % of total coliforms, fecal coliforms and E.coli in wastewater at various scales, and leachate copper concentrations were determined to be below Canadian guideline values for outfall. This study successfully implemented the "structure" strategy of process intensification, and opens up the possibility to apply micro-structured copper foam in a range of other water disinfection systems, from pre-treatment to point-of-use, and should thus become a topic of further research.

Antimicrobial Copper-Based Materials and Coatings: Potential Multifaceted Biomedical Applications

Surface contamination by microbes leads to several detrimental consequences like hospital- and device-associated infections. One measure to inhibit surface contamination is to confer the surfaces with antimicrobial properties. Copper's antimicrobial properties have been known since ancient times, and the recent resurgence in exploiting copper for application as antimicrobial materials or coatings is motivated by the growing concern about antibiotic resistance and the pressure to reduce antibiotic use. Copper, unlike silver, demonstrates rapid and high microbicidal efficacy against pathogens that are in close contact under ambient indoor conditions, which enhances its range of applicability. This review highlights the mechanisms behind copper's potent antimicrobial property, the design and fabrication of different copper-based antimicrobial materials and coatings comprising metallic copper/copper alloys, copper nanoparticles or ions, and their potential for practical applications. Finally, as the antimicrobial coatings market is expected to grow, we offer our perspectives on the implications of increased copper release into the environment and the potential ecotoxicity effects and possibility of development of resistant genes in pathogens.

In vitro evaluation of antimicrobial efficacy and durability of three copper surfaces used in healthcare

Antimicrobial properties of solid copper (Cu) surfaces against various microorganisms have been demonstrated, but little is known about the durability and relative antimicrobial efficacy of different Cu formulations currently used in healthcare. The aim of this study was to assess whether three different formulations of copper-bearing alloys (integral, spray-on and Cu-impregnated surfaces) and a stainless steel control differed in their antimicrobial efficacy, durability, and compatibility with hospital-grade cleaner/disinfectants. The U.S. Environmental Protection Agency draft protocol for the evaluation of bactericidal activity of Cu containing alloys was modified to more accurately reflect cleaning methods in healthcare. The three different Cu alloys were evaluated using 25 × 25 × 3 mm disks subjected to one year of simulated cleaning and disinfection using the Wiperator™ with microfiber cloths presoaked in three common hospital disinfectants: accelerated hydrogen peroxide, quaternary ammonium, or sodium hypochlorite solutions. Bactericidal activity was evaluated using Staphylococcus aureus and Pseudomonas aeruginosa. While all Cu formulations exhibited some antimicrobial activity, integral and spray-on Cu alloys showed the greatest efficacy. Assessments of durability included documentation of changes in mass, morphological changes by scanning electron microscopy, chemical composition alteration by energy-dispersive x-ray spectroscopy, and surface roughness alteration using profilometry over one year of simulated use. The integral Cu alloy had the least mass loss (0.20% and 0.19%) and abrasion-corrosion rate (6.28 and 6.09 μm/yr) compared to stainless steel. The integral product also showed the highest durability. Exposure to disinfectants affected both the antimicrobial efficacy and durability of the various copper products.

Co-crystallization of antibacterials with inorganic salts: paving the way to activity enhancement

Co-crystallization of the antibacterial agents proflavine and methyl viologen with the inorganic salts CuCl, CuCl₂ and AgNO₃ results in enhanced antimicrobial activity with respect to the separate components.

Electrochemical Preparation of Synergistic Nanoantimicrobials

The rapid spreading of resistance among common bacterial pathogens towards the misused antibiotics/disinfectant agents has drawn much attention worldwide to bacterial infections. In light of this, the present work aimed at the realization of core-shell nanoparticles possessing remarkable antimicrobial properties thanks to the synergistic action of the metal core and the disinfectant shell. Copper nanoparticles stabilized by benzalkonium chloride were prepared, characterized, and implemented in poly-vinyl-methyl ketone to obtain nanoantimicrobial composite coatings. Bioactivity tests are reported, proving the excellent disinfectant properties of the proposed nanomaterials, as compared to one of the well-known and strongest silver-based nanoantimicrobials. Applications are also briefly described.

Adaptation of metal and antibiotic resistant traits in novel β-Proteobacterium Achromobacter xylosoxidans BHW-15

Chromosomal co-existence of metal and antibiotic resistance genes in bacteria offers a new perspective to the bacterial resistance proliferation in contaminated environment. In this study, an arsenotrophic bacterium Achromobacter xylosoxidans BHW-15, isolated from Arsenic (As) contaminated tubewell water in the Bogra district of Bangladesh, was analyzed using high throughput Ion Torrent Personal Genome Machine (PGM) complete genome sequencing scheme to reveal its adaptive potentiality. The assembled draft genome of A. xylosoxidans BHW-15 was 6.3 Mbp containing 5,782 functional genes, 1,845 pseudo genes, and three incomplete phage signature regions. Comparative genome study suggested the bacterium to be a novel strain of A. xylosoxidans showing significant dissimilarity with other relevant strains in metal resistance gene islands. A total of 35 metal resistance genes along with arsenite-oxidizing aioSXBA, arsenate reducing arsRCDAB, and mercury resistance merRTPADE operonic gene cluster and 20 broad range antibiotic resistance genes including β-lactams, aminoglycosides, and multiple multidrug resistance (MDR) efflux gene complex with a tripartite system OM-IM-MFP were found co-existed within the genome. Genomic synteny analysis with reported arsenotrophic bacteria revealed the characteristic genetic organization of ars and mer operonic genes, rarely described in β-Proteobacteria. A transposon Tn21 and mobile element protein genes were also detected to the end of mer (mercury) operonic genes, possibly a carrier for the gene transposition. In vitro antibiotic susceptibility assay showed a broad range of resistance against antibiotics belonging to β-lactams, aminoglycosides, cephalosporins (1st, 2nd, and 3rd generations), monobactams and even macrolides, some of the resistome determinants were predicted during in silico analysis. KEGG functional orthology analysis revealed the potential of the bacterium to utilize multiple carbon sources including one carbon pool by folate, innate defense mechanism against multiple stress conditions, motility, a proper developed cell signaling and processing unit and secondary metabolism-combination of all exhibiting a robust feature of the cell in multiple stressed conditions. The complete genome of the strain BHW-15 stands as a genetic basis for the evolutionary adaptation of metal and the antibiotic coexistence phenomenon in an aquatic environment.

Structure-function relationships of nonviral gene vectors: Lessons from antimicrobial polymers

In recent years, substantial advances have been achieved in the design and synthesis of nonviral gene vectors. However, lack of effective and biocompatible vectors still remains a major challenge that hinders their application in clinical settings. In the past decade, there has been a rapid expansion of cationic antimicrobial polymers, due to their potent, rapid, and broad-spectrum biocidal activity against resistant microbes, and biocompatible features. Given that antimicrobial polymers share common features with nonviral gene vectors in various aspects, such as membrane affinity, functional groups, physicochemical characteristics, and unique macromolecular architectures, these polymers may provide us with inspirations to overcome challenges in the design of novel vectors toward more safe and efficient gene delivery in clinic. Building off these observations, we provide here an overview of the structure-function relationships of polymers for both antimicrobial applications and gene delivery by elaborating some key structural parameters, including functional groups, charge density, hydrophobic/hydrophilic balance, MW, and macromolecular architectures. By borrowing a leaf from antimicrobial agents, great advancement in the development of newer nonviral gene vectors with high transfection efficiency and biocompatibility will be more promising. STATEMENT OF SIGNIFICANCE: The development of gene delivery is still in the preclinical stage for the lack of effective and biocompatible vectors. Given that antimicrobial polymers share common features with gene vectors in various aspects, such as membrane affinity, functional groups, physicochemical characteristics, and unique macromolecular architectures, these polymers may provide us with inspirations to overcome challenges in the design of novel vectors toward more safe and efficient gene delivery in clinic. In this review, we systematically summarized the structure-function relationships of antimicrobial polymers and gene vectors, with which the design of more advanced nonviral gene vectors is anticipated to be further boosted in the future.

Characterization and biological removal of organic compounds from hydraulic fracturing produced water

Hydraulic fracturing generates large volumes of produced water, and treatment of produced water may be necessary for disposal or reuse. Biological treatment of produced water is a potential approach to remove organic constituents and reduce fouling, in conjunction with other treatment processes. This study investigates the biological treatability of produced water samples from the Utica and Bakken Shales using engineered biofilms. Observed total dissolved organic carbon (DOC) removal varied between 1-87% at normalized total dissolved solids concentrations, suggesting that the composition of produced water, including organic constituents and trace elements such as nutrients and metals, is an important driver of biological treatment performance. Mass spectrometric analyses of the DOC composition revealed various alkanes in all samples, but differences in non-ionic surfactant, halogenated, and acidic compound content. Statistical data reduction approaches suggest that the latter two groups are correlated with reduced biodegradation kinetics. These results demonstrate that the combination of biodegradation performance and organic speciation can guide the assessment of the biological treatment of produced water.

Effect of nano-silver, nano-copper, deconex and benzalkonium chloride on biofilm formation and expression of transcription regulatory quorum sensing gene (rh1R) in drug-resistance Pseudomonas aeruginosa burn isolates

BACKGROUND

Biofilm forming drug-resistant Pseudomonas aeruginosa are responsible for major death in burn center of different hospitals across the globe.

OBJECTIVE

The aims of this study were to evaluate the effect of nano-silver (Ag), nano-copper (Cu), and two hospital disinfectants (deconex and benzalkonium chloride) on biofilm formation and expression of transcription regulatory quorum sensing gene rh1R in P. aeruginosa burn isolates.

METHODS

28 multidrug-resistant P. aeruginosa (MDRPA) strains were isolated from patients hospitalized in the burn center of a referral hospital in Kerman, Iran. Sizes and purities of nanoparticles were checked by TEM and X-ray diffraction (XRD) analysis. The Minimal Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) of the nanoparticles (NPs), deconex and benzalkonium chloride were determined by broth microdilution method. Antibiofilm activities of these compounds were measured by microtiter assay. Polymerase chain reaction (PCR) was used for detection of qacEΔ1, cepA, copA and rhlR genes. Quantification of rhlR gene expression in presence and absence of the above compounds was carried out by relative quantitative real-time PCR (qRT-PCR).

RESULTS

Benzalkonium chloride had a potent antimicrobial activity and inhibited growth of all the isolates at MIC 0.06±0.2mg/mL, while nano-Ag was effective at MIC 20±0.2mg/mL. Furthermore, 28.5% of the isolates showed strong, 25% moderate, 14% weak and 32% demonstrated no biofilm activity. Ag NPs exerted highest antibiofilm activity, follow by deconex and benzalkonium chloride. The qacEΔ1 was absent in this study, whereas 17.8% and 60.8% of the isolates were positive for cepA and copA genes. Benzalkonium chloride, Ag NPs and deconex increased the expression of rhlR gene 64, 2 and 7 folds, respectively.

CONCLUSION

Our results suggest that, there is direct relationship between decrease in antibiofilm activity and increase in expression of the rhlR gene in the presence of benzalkonium chloride. Absence of qacEΔ1 gene may be contributed in sensitivity of the isolates to the above agents.

Hydrogels Containing Antibiofilm and Antimicrobial Agents Beneficial for Biofilm-Associated Wound Infection: Formulation Characterizations and In vitro Study

Bacterial biofilm which adheres onto wound surface is shown to be impervious to antibiotics and this in turn delays wound healing. Previous studies showed that antibiofilm agents such as xylitol and ethylenediaminetetraacetic acid (EDTA) prevent bacterial adherence onto surfaces. Formulation of a wound dressing containing antibiofilm agents may be a plausible strategy in breaking the biofilm on wound surfaces and at the same time increase the efficacy of the antibiotic. The purpose of this study was to develop hydrogel formulations containing antibiofilm agents along with antibiotic (gentamicin) for bacterial biofilm-associated wound infection. Sodium carboxymethyl cellulose (NaCMC) hydrogels loaded with antibiofilm agents and antibiotic were prepared. The hydrogels were characterized for their physical properties, rheology, Fourier transform infrared spectroscopy (FTIR), drug content uniformity, differential scanning calorimetry (DSC) and in vitro drug release study. The antibiofilm (Crystal Violet staining and XTT assay) and antibacterial performances of the hydrogels against Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, and Escherichia coli were assessed in vitro. The formulated hydrogels showed adequate release of both antibiofilm agents (xylitol and EDTA). Both antimicrobial and antibiofilm tests showed promising results and demonstrated that the combination of xylitol, EDTA, and gentamicin had an additive effect against both Gram-positive and Gram-negative bacteria. In summary, NaCMC (sodium carboxymethyl cellulose) hydrogels containing the combination of antimicrobial and antibiofilm agents were successfully developed and this can be a new strategy in combating biofilm in wound infection which in turn accelerate wound healing.

Evaluation of the antileishmanial potency, toxicity and phytochemical constituents of methanol bark extract of Sterculia villosa

CONTEXT

Visceral leishmaniasis is a protozoan disease caused by Leishmania donovani parasite. The genus Sterculia (Malvaceae) possesses ethnobotanical potential against this protozoan infection.

OBJECTIVE

Determining the potential role of methanol bark extracts from Sterculia villosa Roxb (SVE) and its phytoconstituents against Leishmania donovani promastigotes.

MATERIALS AND METHODS

SVE was analysed by TLC, UV-Vis, IR spectroscopy and biochemical assays. Antileishmanial potential of SVE (0.5-130 μg/mL for 72 h) was characterized by MTT assay. Fluorescent microscopy was performed to validate the IC₅₀ dose. To determine the effect of SVE on promastigotes, reactive oxygen species (ROS) and superoxide generation, lipid peroxidation and DNA fragmentation assays were performed. Molecular aggregation of compounds was determined by atomic force microscopy (AFM). Extent of cytotoxicity of SVE at IC₅₀ dose was determined against RAW 264.7 macrophages, peritoneal macrophages and murine RBCs. In vivo cytotoxicity of SVE was evaluated in BALB/c mice.

RESULT

SVE exhibited reverse dose dependent antileishmanial activity when 130-0 μg/mL doses were tested against promastigotes. The IC₅₀ and IC₇₀ values were found to be 17.5 and 10 μg/mL, respectively. SVE at IC₅₀ dose demonstrated elevated level of ROS, superoxide, lipid peroxidation and DNA fragmentation against promastigotes with no cytotoxicity. AFM analysis suggested increasing size of molecular aggregation (31.3 nm < 35.2 nm < 2.93 μm) with increase in concentration (10 μg < 17.5 μg < 130 μg).

DISCUSSION AND CONCLUSIONS

The study elucidates the antileishmanial potential of SVE against Leishmania donovani promastigotes by exerting oxidative stress and DNA damage. In sum, SVE can be explored as an immunotherapeutic candidate against leishmaniasis and other infectious diseases.