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Mechanism of copper surface toxicity in Escherichia coli O157:H7 and Salmonella involves immediate membrane depolarization followed by slower rate of DNA destruction which differs from that observed for Gram-positive bacteria
Abstract
We have reported previously that copper I and II ionic species, and superoxide but not Fenton reaction generated hydroxyl radicals, are important in the killing mechanism of pathogenic enterococci on copper surfaces. In this new work we determined if the mechanism was the same in non-pathogenic ancestral (K12) and laboratory (DH5α) strains, and a pathogenic strain (O157), of Escherichia coli. The pathogenic strain exhibited prolonged survival on stainless steel surfaces compared with the other E. coli strains but all died within 10 min on copper surfaces using a 'dry' inoculum protocol (with approximately 10(7) cfu cm(-2) ) to mimic dry touch contamination. We observed immediate cytoplasmic membrane depolarization, not seen with enterococci or methicillin resistant Staphylococcus aureus, and loss of outer membrane integrity, inhibition of respiration and in situ generation of reactive oxygen species on copper and copper alloy surfaces that did not occur on stainless steel. Chelation of copper (I) and (II) ionic species still had the most significant impact on bacterial survival but protection by d-mannitol suggests hydroxyl radicals are involved in the killing mechanism. We also observed a much slower rate of DNA destruction on copper surfaces compared with previous results for enterococci. This may be due to protection of the nucleic acid by the periplasm and the extensive cell aggregation that we observed on copper surfaces. Similar results were obtained for Salmonella species but partial quenching by d-mannitol suggests radicals other than hydroxyl may be involved. The results indicate that copper biocidal surfaces are effective for Gram-positive and Gram-negative bacteria but bacterial morphology affects the mechanism of toxicity. These surfaces could not only help to prevent infection spread but also prevent horizontal gene transmission which is responsible for the evolution of virulent toxin producing and antibiotic resistant bacteria.
... This finding suggests that the development of copper resistance is unlikely. Warnes et al. confirmed their previous results in other works and added that the membrane depolarization occurs after cell death [153,154]. ...
... In contrast, in Gramnegative bacteria, due to the protection of nucleic acid by the periplasm, the access of copper ions to DNA is restricted until the cytoplasmic membrane becomes disintegrated. As such, the first hypothesis is more likely in this case [153]. Nevertheless, Santo et al. [155] reported that the antibacterial mode of stress for copper is not dependent on the structural difference in the cell wall, and all bacteria are killed as a result of extensive membrane damage. ...
... In the previous sections, the two modes of stress exerted by copper on bacteria were described, and it was discussed that membrane damage could occur. However, several researchers believe that this may not be the primary target of copper [150,[152][153][154]. ...
Titanium (Ti) has been widely used for manufacturing of bone implants because of its mechanical properties, biological compatibility, and favorable corrosion resistance in biological environments. However, Ti implants are prone to infection (peri-implantitis) by bacteria which in extreme cases necessitate painful and costly revision surgeries. An emerging, viable solution for this problem is to use copper (Cu) as an antibacterial agent in the alloying system of Ti. The addition of copper provides excellent antibacterial activities, but the underpinning mechanisms are still obscure. This review sheds light on such mechanisms and reviews how incorporation of Cu can render Ti–Cu implants with antibacterial activity. The review first discusses the fundamentals of interactions between bacteria and implanted surfaces followed by an overview of the most common engineering strategies utilized to endow an implant with antibacterial activity. The underlying mechanisms for antibacterial activity of Ti–Cu implants are then discussed in detail. Special attention is paid to contact killing mechanisms because the misinterpretation of this mechanism is the root of discrepancies in the literature.
... Another feature of the antibacterial activity of copper and its alloys is that only a few copper-resistant bacteria have been reported. This may be related to the degradation of bacterial nucleic acids observed on copper and its alloy surfaces [12][13][14][15][16][17][18]. Bacteria have the ability of horizontal gene transfer (HGT), which can occur on touch surfaces. ...
... For its further utilization and optimization, it is important to appropriately evaluate the nucleic acids degradability of materials as well as to investigate its mechanism. In order to evaluate the fragmentation of bacterial genes, electrophoresis of nucleic acids extracted from the bacteria applied onto the material surface is mostly performed [12,[14][15][16][17][18], but a quantitative evaluation is difficult since bacterial numbers will change at the material surface depending on its antibacterial activity. There is no quantitative evaluation method of a material's ability to degrade nucleic acids on its surface. ...
... Dominancy or sequences among these processes remains unclear; it may be different depending on the type of microorganisms [4]. As described before, the degradation of bacterial genes is considered as beneficial to inhibit HGT of antibiotic-resistant genes and confirmed by electrophoresis of nucleic acids extracted from bacteria applied to the copper surface [12][13][14][15][16][17][18]. However, this method has a limitation on its quantitativeness since the amount of extracted nucleic acids will be influenced by the difference in the number of viable cells recovered from the copper and the reference material. ...
Copper (Cu) and its alloys have bactericidal activity known as “contact killing” with degradation of nucleic acids inside the bacteria, which is beneficial to inhibit horizontal gene transfer (HGF). In order to understand the nucleic acid degradability of Cu and its alloy surfaces, we developed a new in vitro method to quantitatively evaluate it by a swab method under a “dry” condition and compared it with that of commercially available antibacterial materials such as antibacterial stainless steel, pure silver, and antibacterial resins. As a result, only Cu and its alloys showed continuous degradation of nucleic acids for up to 6 h of contact time. The nucleic acid degradability levels of the Cu alloys and other antibacterial materials correlate to their antibacterial activities evaluated by a film method referring to JIS Z 2801:2012 for Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria. Nucleic acid degradation by copper (I) and (II) chlorides was confirmed at the ranges over 10 mM and 1–20 mM, respectively, suggesting that the copper ion release may be responsible for the degradation of the nucleic acids on Cu and its alloy surfaces. In conclusion, the higher Cu content in the alloys gave higher nucleic acid degradability and higher antibacterial activities.
... Numerous studies have demonstrated the antibacterial and antiviral activity of copper against a wide range of pathogens including E. coli, Influenza A, Norovirus, SARS-CoV-1, herpes simplex, Junin, HIV-1, poliovirus, monkeypox, and Marburg and Ebola viruses (Champagne et al. 2019;Cortes and Zuñiga 2020;Govind et al. 2021;Grass et al. 2011;Han et al. 2005;Imai et al. 2012;Mantlo et al. 2020;Manuel et al. 2015;Michels et al. 2015;Montero et al. 2019;Noyce et al. 2007;Rakowska et al. 2021;Rosenberg et al. 2018;Różańska et al. 2017;Warnes et al. 2012;Wilks et al. 2005). In addition, laboratory results have led to the use of copper materials in clinical trials in healthcare facilities and community centers (Casey et al. 2010;Colin et al. 2018;Hinsa-Leasure et al. 2016;Ibrahim et al. 2018;Poggio et al. 2020;Zerbib et al. 2020;Schmidt et al. 2012), with hospital intensive care units containing copper-coated appliances reporting 83-99.9% ...
... reduction in the burden of pathogens and infections (Montero et al. 2019;Salgado et al. 2013). The exact mechanism behind the ability of copper to inactivate or kill pathogens is believed to differ between pathogen types (Festa and Thiele 2011;Manuel et al. 2015;Rosenberg et al. 2018;Warnes et al. 2012Warnes et al. , 2015. For viruses, the proposed mechanism is that copper ions disrupt viral envelopes, prevent cellular respiration, produce free radicals, and destroy the DNA/RNA of microbes when in contact with copper surfaces (Rakowska et al. 2021). ...
SARS-CoV-2 is a highly infectious virus and etiologic agent of COVID-19, which is spread by respiratory droplets, aerosols, and contaminated surfaces. Copper is a known antiviral agent, and has resulted in successful reduction of pathogens and infections by 83-99.9% when coated on surfaces in intensive care units. Additionally, copper has been shown to inactivate pathogens such as Coronavirus 226E, a close relative of SARS-CoV-2. Here, we examine the ability of two copper blends with differing compositions to inactivate SARS-CoV-2 virus at different time points. Copper Blend 2 (75.07% pure copper) was found to significantly reduce (over 50%) the viability of SARS-CoV-2 at 5 min of contact, with at least 98% reduction in recovered virus at 20 min (vs. plastic control). However, Copper Blend 1 (48.26% pure copper), was not found to significantly reduce viability of SARS-CoV-2 at any time point when compared to plastic. This may indicate that there is an important percentage of copper content in materials that is needed to effectively inactivate SARS-CoV-2. Overall, this study shows that over the course of 20 min, coatings made of copper materials can significantly reduce the recovery of infectious SARS-CoV-2 compared to uncoated controls, indicating the effective use of copper for viral inactivation on surfaces. Furthermore, it may suggest higher copper content has stronger antiviral properties. This could have important implications when short turnaround times are needed for cleaning and disinfecting rooms or equipment, especially in strained healthcare settings which are struggling to keep up with demand.
... Here, CFS from L. rhamnosus SCB0119 accumulated the ROS levels in E. coli ATCC25922 and S. aureus ATCC6538, which was similar to the increases of ROS production in S. typhimurium caused by CFS from L. rhamnosus SQ511 [20]. The high level of ROS production causes oxidative stress, which is closely associated with adverse effects on cellular components and causes cell death [25,26]. ...
... Secondly, nickel is an essential catalytic cofactor of enzymes allowing organisms to inhabit diverse environmental niches, and its pumping through the cytoplasmic membrane is regulated by NikABCDE [38]. Iron intake positively correlated with the synthesis of some ferritin proteins, such as catalases, whose reduction will cause the intracellular accumulation of H 2 O 2 , induce the oxidative stress response inside the thallus, and bring adverse effects on cellular components such as DNA, proteins, and membrane lipids [26,39,40]. The deletion of E. coli fepD caused a reduction in iron intake [41]. ...
Lactic acid bacteria were reported as a promising alternative to antibiotics against pathogens. Among them, Lactobacillus rhamnosus could be used as probiotics and inhibit several pathogens, but its antibacterial mechanisms are still less known. Here, L. rhamnosus SCB0119 isolated from fermented pickles could inhibit bacterial growth or even cause cell death in Escherichia coli ATCC25922 and Staphylococcus aureus ATCC6538, which was mainly attributed to the cell-free culture supernatant (CFS). Moreover, CFS induced the accumulation of reactive oxygen species and destroyed the structure of the cell wall and membrane, including the deformation in cell shape and cell wall, the impairment of the integrity of the cell wall and inner membrane, and the increases in outer membrane permeability, the membrane potential, and pH gradient in E. coli and S. aureus. Furthermore, the transcriptomic analysis demonstrated that CFS altered the transcripts of several genes involved in fatty acid degradation, ion transport, and the biosynthesis of amino acids in E. coli, and fatty acid degradation, protein synthesis, DNA replication, and ATP hydrolysis in S. aureus, which are important for bacterial survival and growth. In conclusion, L. rhamnosus SCB0119 and its CFS could be used as a biocontrol agent against E. coli and S. aureus.
... Among the hybrid samples, only the Ti 0.54 Cu 0.46 induced significant bactericidal effect (approximately 2 log 10 reductions for E. coli and 1 log 10 reduction for S. aureus), while the other, Ti 0.74 Cu 0.26 and Ti 0.70 Cu 0.30 , showed bacterial reduction values comparable to the Ti sample. The copper action mechanism against bacteria depends on the release of copper ions into the medium, which inhibits cell respiration, induces bacterial membrane disruption, or destroys the intracellular DNA and RNA [28]. This property is important for avoiding the occurrence of resistance since it destroys the machinery for mutation [28]. ...
... The copper action mechanism against bacteria depends on the release of copper ions into the medium, which inhibits cell respiration, induces bacterial membrane disruption, or destroys the intracellular DNA and RNA [28]. This property is important for avoiding the occurrence of resistance since it destroys the machinery for mutation [28]. The material subjected to the presence of bacterial inoculum for 2 h was then analyzed by fluorescence microscopy using a live/dead kit, as depicted in Figure 4a-f. ...
Titanium-copper alloy films with stoichiometry given by Ti1−xCux were produced by magnetron co-sputtering technique and analyzed in order to explore the suitability of the films to be applied as resistive temperature sensors with antimicrobial properties. For that, the copper (Cu) amount in the films was varied by applying different DC currents to the source during the deposition in order to change the Cu concentration. As a result, the samples showed excellent thermoresistivity linearity and stability for temperatures in the range between room temperature to 110 °C. The sample concentration of Ti0.70Cu0.30 has better characteristics to act as RTD, especially the αTCR of 1990 ×10−6°C−1. The antimicrobial properties of the Ti1−xCux films were analyzed by exposing the films to the bacterias S. aureus and E. coli, and comparing them with bare Ti and Cu films that underwent the same protocol. The Ti1−xCux thin films showed bactericidal effects, by log10 reduction for both bacteria, irrespective of the Cu concentrations. As a test of concept, the selected sample was subjected to 160 h reacting to variations in ambient temperature, presenting results similar to a commercial temperature sensor. Therefore, these Ti1−xCux thin films become excellent antimicrobial candidates to act as temperature sensors in advanced coating systems.
... The mechanisms of Cu-mediated contact killing are not fully understood, but it has been generally accepted that toxic Cu + ions are the major cause of cell death (Vincent et al., 2018). Copper ions disrupt bacterial membrane integrity and further damage DNAs in the cytoplasm (Hong et al., 2012;Molteni et al., 2010;Warnes et al., 2012). However, the free Cu 2+ ion concentrations on metallic Cu are not high enough to kill bacteria, and direct physical contact between bacteria and copper was shown to be crucial for the antimicrobial activities (Mathews et al., 2013;Molteni et al., 2010). ...
... Metabolism (442) Regulator (160) Secreted Protein (77) Cell Motility (35) Siderophore (25) EPS & Cell Envelope (50) Transporter (268) Others ( We showed that Cu + ions were mutagenic as we would expect based on their toxic effects on genomic DNAs (Warnes et al., 2012). ...
Abstract Antimicrobial copper‐containing surface materials have a great potential of reducing the risks of healthcare‐associated infections (HAIs), but their increased use in hospital facilities may select copper‐resistant strains, causing concerns to antimicrobial resistance management. Here, we describe a long‐term bacterial evolution experiment wherein a non‐pathogenic Pseudomonas strain was subjected to daily transfer in laboratory media with and without copper‐mediated contact killing. The copper treatment sequentially involved two surface materials differing in Cu content and thus contact killing effectiveness: first on brass (Cu 63.5%) and then on pure copper (Cu 99.9%). A gradual increase in bacterial survival rate (or a decrease of killing effectiveness) was observed over time on the related copper surfaces. For the final evolved populations after 320 transfers, 37.8% cells of the copper‐evolved populations were able to survive 60 min on pure copper, whereas populations in the control lines remained sensitive with a survival rate of 0.09% under the same contact killing condition. Genome re‐sequencing revealed ~540 mutations accumulated in the copper lines but only 71, on average, in the control lines (variant frequency > 0.5). The mutagenic activities of Cu+ ions were confirmed by measuring spontaneous mutation rate in a laboratory medium supplemented with copper sulfate at a non‐inhibitory concentration. The copper‐evolved populations have acquired increased resistance to Cu+ ions and tobramycin (an aminoglycoside antibiotic), but showed decreased production of biofilm, exoprotein, and pyoverdine. Together, our data demonstrate the potential of bacteria to evolve prolonged survival on metallic copper, and the long‐term impacts should be considered with increased copper usage in hospital environments.
... When the potential difference drops to zero, it will cause membrane leakage or even rupture, exposure of the cellular components, and, eventually, bacterial death (75). Many studies have shown that the cell membrane is a direct target of copper exposure (76,77). Hong et al. (78) found that E. coli died after 45 min of copper alloy contact, but no degradation of genomic DNA was observed. ...
... Tian et al. (106) demonstrated that the Enterobacter cell structure was severely degraded after exposure to the dry copper surface for 30 s. Moreover, compared to wet conditions, copper kills Enterococcus 80% to 90% faster under dry conditions (77). In the case of contact killing, the antimicrobial effect of copper is not related to the dissolution of copper but the copper content on the contact surface (107). ...
Copper has been used as an antimicrobial agent long time ago. Nowadays, copper-containing nanoparticles (NPs) with antimicrobial properties have been widely used in all aspects of our daily life. Copper-containing NPs may also be incorporated or coated on the surface of dental materials to inhibit oral pathogenic microorganisms. This review aims to detail copper-containing NPs’ antimicrobial mechanism, cytotoxic effect and their application in dentistry.
... When the potential difference reaches zero, membrane leakage or rupture, exposure of cellular components, and, ultimately, bacterial death will occur [37]. Numerous studies have demonstrated that copper exposure directly affects the cell membrane [38,39]. ...
Citation: Salvo, J.; Sandoval, C.; Schencke, C.; Acevedo, F.; del Sol, M. Healing Effect of a Nano-Functionalized Medical-Grade Honey for the Treatment of Infected Wounds. Pharmaceutics 2023, 15, 2187. Abstract: Based on the qualities of Ulmo honey (Eucryphia cordifolia), a medical-grade honey (Ulmoplus ®) has been developed. Relevant to this, the use of copper represents an emerging therapy for the treatment of wounds. Therefore, the aim of this study was to see how this medical-grade honey with copper nanoparticles (CuNPs) helped to heal infected or non-infected wounds. Twenty-four guinea pigs (Cavia porcellus) were divided into four groups for phase 1 (without and with infection, U + F 1 and U + F 2), and two groups for phase 2 (selected formulation, without and with infection, U + F 2 NI and U + F 2 I). Bacteriological and histopathological studies, collagen fibers content evaluation, and stereological analysis were performed. The selected formulation displayed the same antibacterial potency as Ulmoplus ® , indicating that this medical-grade honey by itself can be used as an antibacterial agent. However, the evaluation of collagen content demonstrated a significant increase in fibroblast and type III collagen fibers for infected and uninfected groups, which correlated with the histopathological study. Therefore, it is correct to affirm that adding CuNPs to Ulmoplus ® improved the maturation of collagen fibers. Finally, polymorphonuclear cells presented similar values between experimental groups, which would indicate that the formulation under study was able to regulate the inflammatory process despite their infectious condition.
... Table 3 summarizes studies on copper toxicity on surfaces, as nanoparticles, and in solu- The effect of copper surfaces on bacterial respiration has also been reported on vancomycin-resistant Enterococcus species in a process associated with cytochrome inhibition by copper ions released from the surface [39]. reported that in E. coli O157: H7 and Salmonella, the damage caused by hydroxyl radicals is not the primary toxicity mechanism of copper surfaces [114]. The authors mainly refer to the damage occurring on the outer membrane since it is the cellular structure that interacts the most with the surface. ...
Copper is a metal historically used to prevent infections. One of the most relevant challenges in modern society are infectious disease outbreaks, where copper-based technologies can play a significant role. Currently, copper nanoparticles and surfaces are the most common antimicrobial copper-based technologies. Despite the widespread use of copper on nanoparticles and surfaces, the toxicity mechanism(s) explaining their unique antimicrobial properties are not entirely known. In general, toxicity effects described in bacteria and fungi involve the rupture of membranes, accumulation of ions inside the cell, protein inactivation, and DNA damage. A few studies have associated Cu-toxicity with ROS production and genetic material degradation in viruses. Therefore, understanding the mechanisms of the toxicity of copper nanoparticles and surfaces will contribute to developing and implementing efficient antimicrobial technologies to combat old and new infectious agents that can lead to disease outbreaks such as COVID-19. This review summarizes the current knowledge regarding the microbial toxicity of copper nanoparticles and surfaces and the gaps in this knowledge. In addition, we discuss potential applications derived from discovering new elements of copper toxicity, such as using different molecules or modifications to potentiate toxicity or antimicrobial specificity.
... The mechanism may be that when Cu2+ is present as a free ion, it will generate highly toxic hydroxyl radicals from hydrogen peroxide and superoxide [205,206]. The generated hydroxyl radicals can oxidize with most bacterial macromolecules to exert antibacterial effects [207,208]. In addition, Cu2+ can be associated with affecting the bacterial outer membrane potential, leading to the rupture of the bacterial membrane, and eventually to bacterial death. ...
The regeneration of biological tissues in medicine is challenging, and 3D bioprinting offers an innovative way to create functional multicellular tissues. One common way in bioprinting is bioink, which is one type of the cell-loaded hydrogel. For clinical application, however, the bioprinting still suffers from satisfactory performance, e.g., in vascularization, effective antibacterial, immunomodulation, and regulation of collagen deposition. Many studies incorporated different bioactive materials into the 3D-printed scaffolds to optimize the bioprinting. Here, we reviewed a variety of additives added to the 3D bioprinting hydrogel. The underlying mechanisms and methodology for biological regeneration are important and will provide a useful basis for future research.
... This allows the effect of the nanoparticles to be amplified even further. Nanoparticles molecules demonstrated that the destruction of plasmid genomic DNA has an effect on the prevention of the spread of infection and gene transfer [33]. ...
Klebsiella pneumoniae, ESBLs, Biosynthesized Ag-NPs, blaCTX, blaTEM, entB, htrA. Klebsiella pneumoniae bacteria were isolated from different sources; urine, blood, burns and wound swab, sputum, ear swabs, fluid, pus, endotracheal swabs, CSF and abscess of biopsy as (37, 24, 16, 9, 4, 3, 3, 2, and 1) % respectively. It showed different levels of antibiotic resistance with highest level of resistance against Ampicillin (100 %), also it showed that 53.13% of isolates were positive and 46.87% were negative for producing of β-lactamase. Biosynthesized Ag-NPs has inhibitory action (MIC) against K. pneumoniae with concentration 10 mM and sub-MIC with concentration 5mM. XRD spectrum of silver nanoparticles exhibited at 2ø (32.5°) corresponds to the (101) plane of conventional XRD data of Ag-NPs Crystals, while FTIR analysis was showed that stretch for Ag-NPs discovered around 518.58 cm-1. All isolates (100%) were positive to htrA, entB, blaCTX, and blaTEM before treatment with silver nanoparticles, but genes of htrA, entB, and blaTEM disappeared in the isolate no.1 after treatment with Ag-NPs at concentration (5mM). After gene sequence, the results have shown that before treatment with AgNPs, htrA, entB, blaCTX, and blaTEM genes were identical (100%) with NCBI, while after treatment with AgNPs in concentration (5 and 10) mM these genes were not affected. This work is licensed under a Creative Commons Attribution Non-Commercial 4.0 International License.
... However, K(AbS) values were similar in the case of these bacteria. For E. faecalis, high K(AbS) was observed for all combinations that may be the result of faster rate of DNA destruction by Cu components compared to Enterobacteria (such as E. coli) 25 . ...
Bacterial infections are one of the leading causes of death worldwide. In the case of topical bacterial infections such as wound infections, silver (Ag) has historically been one of the most widely used antibacterials. However, scientific publications have demonstrated the adverse effects of silver on human cells, ecotoxicity and insufficient antibacterial effect for the complete elimination of bacterial infections. The use of Ag in the form of nanoparticles (NPs, 1–100 nm) allows to control the release of antibacterial Ag ions but is still not sufficient to eliminate infection and avoid cytotoxicity. In this study, we tested the potency of differently functionalized copper oxide (CuO) NPs to enhance the antibacterial properties of Ag NPs. The antibacterial effect of the mixture of CuO NPs (CuO, CuO–NH2 and CuO–COOH NPs) with Ag NPs (uncoated and coated) was studied. CuO and Ag NP combinations were more efficient than Cu or Ag (NPs) alone against a wide range of bacteria, including antibiotic-resistant strains such as gram-negative Escherichia coli and Pseudomonas aeruginosa as well as gram-positive Staphylococcus aureus, Enterococcus faecalis and Streptococcus dysgalactiae. We showed that positively charged CuO NPs enhanced the antibacterial effect of Ag NPs up to 6 times. Notably, compared to the synergy of CuO and Ag NPs, the synergy of respective metal ions was low, suggesting that NP surface is required for the enhanced antibacterial effect. We also studied the mechanisms of synergy and showed that the production of Cu⁺ ions, faster dissolution of Ag⁺ from Ag NPs and lower binding of Ag⁺ by proteins of the incubation media in the presence of Cu²⁺ were the main mechanisms of the synergy. In summary, CuO and Ag NP combinations allowed increasing the antibacterial effect up to 6 times. Thus, using CuO and Ag NP combinations enables to retain excellent antibacterial effects due to Ag and synergy and enhances beneficial effects, since Cu is a vital microelement for human cells. Thus, we suggest using combinations of Ag and CuO NPs in antibacterial materials, such as wound care products, to increase the antibacterial effect of Ag, improve safety and prevent and cure topical bacterial infections.
... Because the vast majority of research has been done on the action of bacteria, there are very few findings that specifically discuss the antifungal mechanisms of metal NPs (Beyth et al., 2015;Chiriac et al., 2016;Warnes et al., 2012;Jangjou et al., 2022b). As a consequence of this, the function that these NPs play as antifungal agents is still a matter of debate. ...
Metallic nanoparticles (NPs) are of particular interest as antimicrobial agents in water and wastewater treatment due to their broad suppressive range against bacteria, viruses, and fungi commonly found in these environments. This review explores the potential of different types of metallic NPs, including zinc oxide, gold, copper oxide, and titanium oxide, for use as effective antimicrobial agents in water and wastewater treatment. This is due to the fact that metallic NPs possess a broad suppressive range against bacteria, viruses, as well as fungus. In addition to that, NPs are becoming an increasingly popular alternative to antibiotics for treating bacterial infections. Despite the fact that most research has been focused on silver NPs because of the antibacterial qualities that are known to be associated with them, curiosity about other metallic NPs as potential antimicrobial agents has been growing. Zinc oxide, gold, copper oxide, and titanium oxide NPs are included in this category since it has been demonstrated that these elements have antibacterial properties. Inducing oxidative stress, damage to the cellular membranes, and breakdowns throughout the protein and DNA chains are some of the ways that metallic NPs can have an influence on microbial cells. The purpose of this review was to engage in an in-depth conversation about the current state of the art regarding the utilization of the most important categories of metallic NPs that are used as antimicrobial agents. Several approaches for the synthesis of metal-based NPs were reviewed, including physical and chemical methods as well as “green synthesis” approaches, which are synthesis procedures that do not involve the employment of any chemical agents. Moreover, additional pharmacokinetics, physicochemical properties, and the toxicological hazard associated with the application of silver NPs as antimicrobial agents were discussed.
... High concentrations of ions (especially copper) bind to both the inner and outer parts of the bacterial cell membrane, lipopolysaccharides, peptidoglycans, and carboxylic groups, reducing the potential difference between intracellular and extracellular components, causing depolarization and instability in the cell membrane. 41 The result is the rupture of the cell membrane and disintegration of bacteria. 42 Additionally, metallic nanoparticles can generate ROS that induces cellular oxidative damage by causing DNA/RNA breakage, protein oxidative carbonylation, membrane disruption, and lipid peroxidation, eventually leading to the death of microorganisms. ...
Bacteria cause many common infections and are the culprit of many outbreaks throughout history that have led to the loss of millions of lives. Contamination of inanimate surfaces in clinics, the food chain, and the environment poses a significant threat to humanity, with the increase in antimicrobial resistance exacerbating the issue. Two key strategies to address this issue are antibacterial coatings and effective detection of bacterial contamination. In this study, we present the formation of antimicrobial and plasmonic surfaces based on Ag-CuxO nanostructures using green synthesis methods and low-cost paper substrates. The fabricated nanostructured surfaces exhibit excellent bactericidal efficiency and high surface-enhanced Raman scattering (SERS) activity. The CuxO ensures outstanding and rapid antibacterial activity within 30 min, with a rate of >99.99% against typical Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacteria. The plasmonic Ag nanoparticles facilitate the electromagnetic enhancement of Raman scattering and enables rapid, label-free, and sensitive identification of bacteria at a concentration as low as 103 cfu/mL. The detection of different strains at this low concentration is attributed to the leaching of the intracellular components of the bacteria caused by the nanostructures. Additionally, SERS is coupled with machine learning algorithms for the automated identification of bacteria with an accuracy that exceeds 96%. The proposed strategy achieves effective prevention of bacterial contamination and accurate identification of the bacteria on the same material platform by using sustainable and low-cost materials.
... In this research, Shigella flexneri strain IrCis5 was treated with the addition of dye and copper which caused stress. When bacteria are exposed to copper, bacterial cellular respiration will be affected, and degradation of bacterial DNA occurs (Warnes et al., 2011). The decrease in decolorization ability is also thought to be caused by excessive stress faced by ...
Dyes and copper are dangerous contaminants because they are toxic. Bioremediation using indigenous bacteria is the best solution to overcome water pollution. Copper resistant bacteria usually have resistance to dyes thereby helping the bioremediation of dye and copper wastes. This study aims to examine the ability of indigenous bacteria isolated from the Cisadane River, namely Klebsiella grimontii IrCis3, Shigella flexneri IrCis5, Enterobacter cloacae IrCis6, and Enterobacter cloacae IrCis9 in terms of resistance and ability to decolorize 12 textile dyes namely methylene blue, malachite green, congo red, mordant orange, reactive black, direct yellow, basic fuchsin, reactive orange, dispersed orange, remasol red, wantex yellow and wantex red. The results showed that Shigella flexneri IrCis5, Enterobacter cloacae IrCis6, and Enterobacter cloacae IrCis9 were resistant to all dye concentrations of 200 and 500 ppm except Klebsiella grimontii IrCis3 did not grow on malachite green and basic fuchsin at concentrations of 200 ppm and methylene blue, malachite green and basic fuchsin concentration of 500 ppm. Only Shigella flexneri IrCis5 has the ability to decolorize 200 ppm basic fuchsin up to 87.23% after 3 days of incubation. The addition of 3 mM CuSO4 reduced the ability to decolorize Shigella flexneri IrCis5 to 0.57%.
... Another inhibitory mechanism for bacterial damage via treatment with CuO-NPs is the overproduction of reactive oxygen species (ROS). These ROS such as superoxide anions, hydrogen peroxides, and hydroxyl radicals, enhance the oxidative stress to amino acids, nucleic acids, and membrane lipids, leading to enzyme deactivation and loss of the selective permeability function [69]. The activity of CuO-NPs toward C. albicans could be related to their efficacy for changing the sterol profile in Candida cell walls via inhibition of ergosterol pathway synthesis [70]. ...
... Another inhibitory mechanism for bacterial damage via treatment with CuO-NPs is the overproduction of reactive oxygen species (ROS). These ROS such as superoxide anions, hydrogen peroxides, and hydroxyl radicals, enhance the oxidative stress to amino acids, nucleic acids, and membrane lipids, leading to enzyme deactivation and loss of the selective permeability function [69]. The activity of CuO-NPs toward C. albicans could be related to their efficacy for changing the sterol profile in Candida cell walls via inhibition of ergosterol pathway synthesis [70]. ...
Herein, the aqueous extract of Portulaca oleracea has been used as a safe, cheap, eco-friendly, and applicable scale-up method to bio-fabricate copper oxide nanoparticles (CuO-NPs). The character of CuO-NPs were determined using UV-vis spectroscopy, Fourier transform infrared (FT-IR), X-ray diffraction (XRD), Transmission electron microscopy (TEM), Energy dispersive X-ray(EDX), Dynamic light scattering (DLS), and zeta potential. Spherical and crystalline CuO-NPs with a size range of 5–30 nm at a maximum surface plasmon resonance of 275 nm were successfully fabricated. The main components of the green-synthesized particles were Cu and O with weight percentages of 49.92 and 28.45%, respectively. A Zeta-potential value of −24.6 mV was recorded for CuO-NPs, indicating their high stability. The plant-based CuO-NPs showed promising antimicrobial and catalytic activity in a dose-dependent manner. Results showed that the synthesized CuO-NPs had the efficacy to inhibit the growth of pathogens Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans with low MIC values in the ranges of 6.25–25 µg/mL. The highest decolorization percentages of tanning wastewater were attained under sunlight irradiation conditions at a concentration of 2.0 mg/mL after 200 min with percentages of 88.6 ± 1.5% compared to those which were recorded under dark conditions (70.3 ± 1.2%). The physicochemical parameters of tanning wastewater including total suspended solids (TSS), total dissolved solids (TDS), chemical oxygen demand (COD), biological oxygen demand (BOD), and conductivity under optimum conditions were significantly decreased with percentages of 95.2, 86.7, 91.4, 87.2, and 97.2%, respectively. Interestingly, the heavy metals including cobalt (Co), lead (Pb), nickel (Ni), cadmium (Cd), and chromium (Cr (VI)) decreased with percentages of 73.2, 80.8, 72.4, 64.4, and 91.4%, respectively, after treatment of tanning wastewater with CuO-NPs under optimum conditions. Overall, the plant-synthesized CuO-NPs that have antimicrobial and catalytic activities are considered a promising nano-catalyst and environmentally beneficial to wastewater treatment.
... The coordination bonding between copper ions and their neighbouring cellulose chains makes this copper ion-textile (Cu-IT) highly stable in air and water, and durable against abrasion. The copper ions can interact with viral genomes and inhibit virus replication 23-25 , and cause contact killing of bacteria and fungi by rupturing cell membranes and inducing reactive oxygen species (ROS) [26][27][28][29] . Cu-IT also shows better mechanical properties, with a ~23% increase in tensile strength compared with unmodified textiles, which is due to the role of the copper ions as 'crosslinkers' between the cellulose molecular chains. ...
Cotton textiles are ubiquitous in daily life and are also one of the primary mediums for transmitting viruses and bacteria. Conventional approaches to fabricating antiviral and antibacterial textiles generally load functional additives onto the surface of the fabric and/or their microfibres. However, such modifications are susceptible to deterioration after long-term use due to leaching of the additives. Here we show a different method to impregnate copper ions into the cellulose matrix to form a copper ion-textile (Cu-IT), in which the copper ions strongly coordinate with the oxygen-containing polar functional groups (for example, hydroxyl) of the cellulose chains. The Cu-IT displays high antiviral and antibacterial performance against tobacco mosaic virus and influenza A virus, and Escherichia coli, Salmonella typhimurium, Pseudomonas aeruginosa and Bacillus subtilis bacteria due to the antimicrobial properties of copper. Furthermore, the strong coordination bonding of copper ions with the hydroxyl functionalities endows the Cu-IT with excellent air/water retainability and superior mechanical stability, which can meet daily use and resist repeated washing. This method to fabricate Cu-IT is cost-effective, ecofriendly and highly scalable, and this textile appears very promising for use in household products, public facilities and medical settings. An antiviral and antibacterial cotton textile based on a fundamentally different principle of incorporating copper ions into the cotton structure at the atomic level is fabricated with excellent air/water retainability and superior mechanical stability.
... The production of Reactive Oxygen Species (ROS) is considered one of the most common outcomes of the interaction between the bacteria and exceeded amount of copper. This is mainly due to the boundary of copper with oxygen and the consecutive formation of peroxide radicals [52,53]. However, contact-killing studies on dry copper alloy surfaces assessed that the first effect of copper on bacteria is represented by the peroxidation of unsaturated fatty acids leading to the disruption of the cellular structure and the failing of the membrane integrity [54][55][56]. ...
Citation: Ghezzi, D.; Sassoni, E.; Boi, M.; Montesissa, M.; Baldini, N.; Graziani, G.; Cappelletti, M. Antibacterial and Antibiofilm Activity of Nanostructured Copper Films Prepared by Ionized Jet Deposition. Antibiotics 2023, 12, 55. Abstract: Metal coatings represent good strategies to functionalize surfaces/devices and limit bacterial contamination/colonization thanks to their pleiotropic activity and their ability to prevent the biofilm formation. Here, we investigated the antibacterial and antibiofilm capacity of copper coatings deposited through the Ionized Jet Deposition (IJD) on the Calgary Biofilm Device (CBD) against the growth of two gram-negative and two gram-positive pathogenic strains. Three areas (i.e., (+)Cu, (++)Cu, and (+++)Cu based on the metal amount) on the CBD were obtained, presenting nanostructured coatings with high surface homogeneity and increasing dimensions of aggregates from the CBD periphery to the centre. The coatings in (++)Cu and (+++)Cu were efficient against the planktonic growth of the four pathogens. This antibacterial effect decreased in (+)Cu but was still significant for most of the pathogens. The antibiofilm efficacy was significant for all the strains and on both coated and uncoated surfaces in (+++)Cu, whereas in (++)Cu the only biofilms forming on the coated surfaces were inhibited, suggesting that the decrease of the metal on the coatings was associated to a reduced metal ion release. In conclusion, this work demonstrates that Cu coatings deposited by IJD have antibacterial and antibiofilm activity against a broad range of pathogens indicating their possible application to functionalize biomedical devices.
... More explicit information regarding the mechanism is presented in Figure 1. Additionally, membrane depolarization is also considered to be one of the main mechanisms of Cu ions' antimicrobial activity (Santo and Lam, 2011;Warnes et al., 2012;Fan et al., 2021). Copper ions can bind to negatively charged regions of the bacterial cell membrane (both outer and inner), reducing the potential difference and causing membrane depolarization. ...
The use of titanium dental implants to replace missing teeth represents an important field of daily dental practice worldwide, which is highly reliable for long-term survival and success rates. However, titanium dental implants still have intrinsic problems that cannot meet the clinical requirements. Improving the performance of implants is an increasingly important area of dental research to reduce infection rates. Improved properties can be achieved by two main methods: 1) the overall change in the materials by changing the elemental composition and 2) surface modifications. This review provides an overview of various titanium-based alloys that have been employed to achieve a higher survival rate of implantation by adding elements or modifying the surface, with a special focus on their antibacterial applications. Recent developments in titanium-based alloys containing various antibacterial agents have been described in detail, including Cu-bearing, Ag-bearing, and Zr-bearing Ti alloys. Moreover, the applications of bioactive coatings and 3D printing materials with antibacterial properties are reviewed. This review aims to highlight the antibacterial challenges associated with titanium-based alloys to promote the further development and clinical application of antibacterial alloys.
... achieved an incredible outcome, wherein as a consequence of placing the bacteria on copper surfaces, the outer membrane integrity was compromised and hydroxyl radicals were produced, respiration was inhibited, and DNA was degraded. [23] Besides, copper appeared to be employed by macrophages and neutrophils for its antibacterial activity within the host. [24,25] In our study, we attempted to determine the copper sensitivity and resistance of Acinetobacter spp. with the aim to better understand the copper-based antimicrobial strategies against Acinetobacter spp. ...
Background: Acinetobacter spp., emerging pathogens equipped with the competence to establish multitudinous severe infections in immunocompromised hosts, are grievous threats to human health. To tackle the enormous burden of disease caused by Acinetobacter spp., the headlong discovery and the advancement of novel therapies are of the essence at this juncture. The present study attempted to determine the antimicrobial effects of copper on the clinical isolates of Acinetobacter spp. (Iso-03 and Iso-04). Methods: The potential deployment of copper-based antibacterial strategies against Acinetobacter spp. was assessed by exposing the isolates to the increasing concentrations of CuSO4 (from 2.5 to 1.5 mM) in liquid culture (M9 minimal medium) for 6 h and also through the exposure of them on solid metal surfaces (stainless steel and copper coupons) for 75 min, wherein the copper sensitivity and resistance of the clinical isolates of Acinetobacter spp. were determined. Results: There was no interference with the growth of the isolates at the low concentrations, whereas the bacterial growth was affected by the high concentrations of CuSO4 at different levels. During the exposure on the solid metal coupons, no loss of viability of isolates was observed on stainless steel, however, the rapid death of isolates was discernible on copper surface, leading to a dramatic decrease in the number of colony-forming units (CFUs), eventually to the limit of detection (3 CFUs per coupon). Conclusion: This study substantiated that copper possesses antimicrobial properties which can be deployed in novel therapies for the prevention of the infections caused by Acinetobacter spp. and other emerging pathogens. Further studies on the sensitivity and resistance of Acinetobacter spp. to copper at the molecular genetics levels can open the door to better exploitation of this metal for the inhibition of the vigorous growth of drug-resistant Acinetobacter spp.
... 17 Even when a "dry" inoculum protocol was employed, E. coli could still be effectively killed by copper surfaces within 30 min owing to the combination of ROS ions and radicals, which leads to damage of the cytoplasmic membrane and degradation of genomic DNA. 18 Studies on copper bulk surfaces also demonstrated that cuprous oxide (Cu 2 O) efficiently inactivates the influenza A virus and E. coli bacteriophage, and cupric oxide (CuO) was less efficient for the same exposure time, indicating that the oxidation state of copper could play an essential role in the efficacy of the biocidal surface. 14,19 Although the antibacterial properties of solid copper surfaces have been the subject of intensive research, the "contact-killing" mechanisms associated with copper NPs remain controversial. ...
The scientific community has recognized that copper can kill bacteria; however, the effect of the particle size, concentration, and oxidation state on antibacterial activity remains unclear for copper and its nanoparticles (NPs), in particular. In this study, copper NP coatings with extremely fast and sustained antibacterial activity are reported. It is found that coating with cuprous oxide (Cu2O) NPs (∼150 nm) and coating with metallic copper NPs (∼50 nm) on commonly used fabrics for cleaning and masks can kill bacteria within 45 s. Our bacterial study was conducted using Staphylococcus aureus as a Gram-positive bacterium and Klebsiella pneumoniae and Pseudomonas aeruginosa as Gram-negative bacteria. Scanning electron micrographs suggest bacterial damage, and bacterial DNA harvested after interaction with copper-coated fabrics indicates DNA fragmentation. On top of this, significantly higher levels of 8-hydroxy-2′-deoxyguanosine are also detected in DNA after interaction with coated fabrics, signifying that both copper and Cu2O NPs rapidly induce oxidative stress. Furthermore, cumulative inoculations with K. pneumoniae for 144 h show excellent sustained bacterial killing in the presence of Cu2O NPs. Using a combination of detailed physical and chemical analysis of the NPs and a study of how bacteria interact with the coated substrate, it is possible to establish the parameters that resulted in speedy and robust antibacterial properties in Cu2O-coated fabrics. This study offers a rational strategy on how to slow down or even halt the transmission of infectious pathogens.
... In addition, copper and its compound were investigated and utilised as a sanitiser for centuries [22]. The bacteria-killing mechanisms of copper may mainly attribute to the cell membrane damage and the ROS (Reactive oxygen species) release leading to the membrane alteration [23], loss of membrane integrity [24], and oxidative stress followed by the degradation of DNA [25]. However, the phagocytes released by the innate immune system response use concentrations of copper to kill bacteria or use chemical means to prevent bacteria from acquiring copper [26]. ...
Antibacterial surfaces in healthcare settings are an important tool for combating the increasing threat of antibacterial drug resistance, which the global Covid-19 pandemic has further exacerbated. Herein, we report a new method to achieve dual antibacterial and flame retardant functionalities in flexible polyurethane foam (PUF) by synthesising a multifunctional coating using a layer-by-layer assembly technique. The coating consists of Ti3C2 nanosheets and chitosan as the flame retardant and metal particles (copper or silver) for the antibacterial property. Results show that the multilayer Ti3C2/CH/Ag coating possesses excellent antibacterial performance with reductions of 99.97% in gram-negative bacteria (P. aeruginosa) and 88.9% in gram-positive bacteria (S. aureus) compared with the unmodified counterpart. Compared with the pristine PUF, the multifunctional coating yielded 66.3% reductions in the PHRR, and demonstrated outstanding smoke suppression performance with a PSPR reduction of 51.6% and a TSR decline of 65.5%. Moreover, Raman spectroscopy revealed an increased graphitisation level in the residual char of the coated foam, indicating the coating's remarkable charring performance. This exceptional multifunctional performance endows the coating technology with a great potential for eradicating the fire risks of antibacterial surfaces in healthcare settings and providing furniture, interior walls and building panels with antibacterial properties.
... When the bacteria were in contact with the microdomain of such a potential difference, the cathodic electrons would consume H + due to the electrochemical potential difference, which is responsible for the bacterial charge transfer process, blocking the respiratory metabolism and energy production of bacteria [51][52][53], as shown in Figure 1. In addition, the overproduction of ROS by the synergistic effect of H + depletion and Cu ions burst release due to the consumption of cathodic electrons would further affect the bio-activities of bacteria, such as membrane damage [54,55], DNA degradation and so on [56]. It is worth noting that since the charge transfer for H + depletion between the cell and substratum is a short-range interaction [57], a sufficient contact between a Cu-bearing stainless steel and bacteria is the key to its antibacterial performance. ...
Metals play an essential role in biochemistry, and the use of metals for antimicrobial applications has been well studied. Biomaterials incorporating copper and silver demonstrated high antimicrobial activity while maintaining good cytocompatibility. In this overview, nanostruc-ture processing is underscored as a method to overcome the shortcomings of conventional bioceramics. Restructuring crystalline structures at the nanoscale make it less susceptible to brittle fracture. Furthermore, the bioactivity of the material is significantly improved through nanoscale surface modifications such as coatings. The effectiveness of nanostructured bioma-terials featuring copper and silver in combatting bacterial attachment and proliferation is described. Nanoscale copper-containing stainless steel achieved antimicrobial activity by disrupting bacterial metabolism and damaging bacterial membranes while providing a conducive environment for cellular proliferation. Copper-containing stainless steels can be used to prevent marine corrosion, food preservation and combat implant-related infections. It is envisaged that future antimicrobial strategies will continue to feature copper and silver nanostructured biomaterials prominently. ARTICLE HISTORY
... Recent research articles reported that metal complexes having copper(II) atom demonstrated efficient antibiofilm potential against gram positive and gram negative bacteria [36,37]. It has been observed that copper ions in the complexes exhibit antibiofilm potential through different mode of actions, remarkably through DNA destruction since intracellular and extracellular genetic materials assumes a crucial role at various levels of biofilm formation and maturation [38]. ...
A polymeric tetrakis N-imidazole copper(II) sulphate complex [Cu(imidazole)4(SO4)]n 1, was synthesized and thoroughly characterized by various spectroscopic techniques, elemental analysis and single crystal X-ray crystallography. X-ray diffraction analysis confirmed that polymer complex 1 crystallized in a monoclinic C2/c space group possessing the lattice constants, a = 9.2213(1) Å, b = 17.6062(3) Å, c = 10.5710(2) Å, α = γ = 90˚ and β = 93.561˚ (1) per unit cell. Hirshfeld surface and DFT calculations were executed to simulate the electronic ground state energies in gas phase which showed that the HOMO and HOMO–1 were distributed on the axially coordinated SO42– moiety and considerable amount of electron density was present on Cu(II). Absorption and emission spectroscopic techniques were used to investigate the binding interaction of the copper(II) imidazole complex with the therapeutic target ct-DNA. The results suggested that the complex 1 binds to the ct-DNA through an electrostatic mode. The gel electrophoresis experiments of 1 were carried out with plasmid pBR322 which revealed that the polymer complex could unwind the plasmid DNA at 30 μM micromolar concentration via discernible oxidative cleavage pathway. Molecular docking studies were also carried out to support the results of DNA binding experiments. In addition, the antimicrobial potential of polymer complex was evaluated against various key pathogens viz., B. subtilis, E. coli, K. pneumonia and S. aureus. Antibiofilm behaviour of the complex 1 was examined against E. coli and S. aureus. The results demonstrated that 1 could act as an active antibacterial agent as it inhibited the bacterial growth in agar plates very efficiently.
... Although the antibacterial mechanism of the solid copper surface has yet to be clearly understood, several studies have investigated the result of the so-called contact killing [8,9]. When bacteria are directly in contact with metallic copper, copper ions accumulate inside the cell because the bacteria recognize the copper ions as essential nutrients [10,11]. The cell and DNA are then damaged and destroyed by the depolarization effect and reactive oxygen species (ROS) [12]. ...
In this work, a copper coating is developed on a carbon steel substrate by exploiting the superwetting properties of liquid copper. We characterize the surface morphology, chemical composition, roughness, wettability, ability to release a copper ion from surfaces, and antibacterial efficacy (against Escherichia coli and Staphylococcus aureus). The coating shows a dense microstructure and good adhesion, with thicknesses of approximately 20–40 µm. X-ray diffraction (XRD) analysis reveals that the coated surface structure is composed of Cu, Cu2O, and CuO. The surface roughness and contact angle measurements suggest that the copper coating is rougher and more hydrophobic than the substrate. Inductively coupled plasma atomic emission spectroscopy (ICP-AES) measurements reveal a dissolution of copper ions in chloride-containing environments. The antibacterial test shows that the copper coating achieves a 99.99% reduction of E. coli and S. aureus. This study suggests that the characteristics of the copper-coated surface, including the chemical composition, high surface roughness, good wettability, and ability for copper ion release, may result in surfaces with antibacterial properties.
... The treatment of C. albicans with Ag-phendione induced extensive smearing of DNA, indicating non-specific cleavage of the DNA [25]. In addition, several studies have reported that copper nanoparticles dramatically affect the bacterial redox systems that culminate with DNA fragmentation [49][50][51]. ...
Tackling microbial resistance requires continuous efforts for the development of new molecules with novel mechanisms of action and potent antimicrobial activity. Our group has previously identified metal-based compounds, [Ag(1,10-phenanthroline-5,6-dione)2]ClO4 (Ag-phendione) and [Cu(1,10-phenanthroline-5,6-dione)3](ClO4)2.4H2O (Cu-phendione), with efficient antimicrobial action against multidrug-resistant species. Herein, we investigated the ability of Ag-phendione and Cu-phendione to bind with double-stranded DNA using a combination of in silico and in vitro approaches. Molecular docking revealed that both phendione derivatives can interact with the DNA by hydrogen bonding, hydrophobic and electrostatic interactions. Cu-phendione exhibited the highest binding affinity to either major (-7.9 kcal/mol) or minor (-7.2 kcal/mol) grooves. In vitro competitive quenching assays involving duplex DNA with Hoechst 33258 or ethidium bromide demonstrated that Ag-phendione and Cu-phendione preferentially bind DNA in the minor grooves. The competitive ethidium bromide displacement technique revealed Cu-phendione has a higher binding affinity to DNA (Kapp=2.55×106 M-1) than Ag-phendione (Kapp=2.79×105 M-1) and phendione (Kapp=1.33×105 M-1). Cu-phendione induced topoisomerase-I-mediated DNA relaxation of supercoiled plasmid DNA. Moreover, Cu-phendione was able to induce oxidative DNA injuries with the addition of free radical scavengers inhibiting DNA damage. Ag-phendione and Cu-phendione avidly displaced propidium iodide bound to DNA in permeabilized Pseudomonas aeruginosa cells in a dose-dependent manner as judged by cytometry. The treatment of P. aeruginosa with bactericidal concentrations of Cu-phendione (15 µM) induced DNA fragmentation as visualized by either agarose gel or TUNEL assays. Altogether, these results highlight a possible novel DNA-targeted mechanism by which phendione-containing complexes, in part, elicit toxicity toward the multidrug-resistant pathogen P. aeruginosa.
... As shown in several studies, nanoscale size allows for the nanoparticles to penetrate microbial cell walls and biofilms layers, causing several events such as irreversible damage of microbial membranes [9,117,118]. Several hypotheses for nanoparticles mechanisms of action have been explored, including cell membrane alterations and disruption [119,120], ROS generation, and lipid peroxidation [121][122][123]. Metabolic pathway disruption is also described as a mechanism of NPs [124,125]. ...
Bacterial biofilms are defined as complex aggregates of bacteria that grow attached to surfaces or are associated with interfaces. Bacteria within biofilms are embedded in a self-produced extracellular matrix made of polysaccharides, nucleic acids, and proteins. It is recognized that bacterial biofilms are responsible for the majority of microbial infections that occur in the human body, and that biofilm-related infections are extremely difficult to treat. This is related with the fact that microbial cells in biofilms exhibit increased resistance levels to antibiotics in comparison with planktonic (free-floating) cells. In the last years, the introduction into the market of novel compounds that can overcome the resistance to antimicrobial agents associated with biofilm infection has slowed down. If this situation is not altered, millions of lives are at risk, and this will also strongly affect the world economy. As such, research into the identification and eradication of biofilms is important for the future of human health. In this sense, this article provides an overview of techniques developed to detect and imaging biofilms as well as recent strategies that can be applied to treat biofilms during the several biofilm formation steps.
... Finally, log reductions were calculated by subtracting the viable counts of bacteria exposed to Cu surfaces from those of bacteria recovered from glass slides. This is an EPA validated procedure [35] and a similar antibacterial testing technique and incubation time has been used by other researchers [1,17,36,37]. ...
Contact surfaces have been identified as one of the main routes for pathogen transmission. The efficacy to kill both viruses and bacteria on touch surfaces is critical to reducing the rampant spread of harmful pathogens. Copper is one such material that has been traditionally used for its antimicrobial properties. However, most contact/touch surfaces are made up of steel or aluminum due to their structural properties. Therefore, coating high-touch components with copper is one possible solution to improve antibacterial efficacy. In this study, copper was coated on both stainless steel and aluminum substrates using a cold spray process which is a fast and economic coating technique. The coated samples in both as-deposited and heat-treated states were exposed to Escherichia coli and Staphylococcus aureus bacteria, and their efficacy was compared with bulk copper plate. It was found that both bacterial cells responded differently to the different coating properties such as coating thickness, porosity, hardness, surface roughness, oxide content, and galvanic coupling effect. These correlations were elucidated in light of various results obtained from antibacterial and bacterial attachment tests, and materials characterizations of the coatings. It is possible to tailor copper coating characteristics to render them more effective against targeted bacteria.
Hybrid metal halide semiconductors are a unique family of materials with immense potential for numerous applications. For this to materialize, environmental stability and toxicity deficiencies must be simultaneously addressed. We report here a porous, visible light semiconductor, namely, (DHS)Bi2I8 (DHS = [2.2.2] cryptand), which consists of nontoxic, earth-abundant elements, and is water-stable for more than a year. Gas- and vapor-sorption studies revealed that it can selectively and reversibly adsorb H2O and D2O at room temperature (RT) while remaining impervious to N2 and CO2. Solid-state NMR measurements and density functional theory (DFT) calculations verified the incorporation of H2O and D2O in the molecular cages, validating the porous nature. In addition to porosity, the material exhibits broad band-edge light emission centered at 600 nm with a full width at half-maximum (fwhm) of 99 nm, which is maintained after 6 months of immersion in H2O. Moreover, (DHS)Bi2I8 exhibits bacteriocidal action against three Gram-positive and three Gram-negative bacteria, including antibiotic-resistant strains. This performance, coupled with the recorded water stability and porous nature, renders it suitable for a plethora of applications, from solid-state batteries to water purification and disinfection.
Cu-bearing stainless steel is widely used in the fields of food, medical and household sanitary equipment because of its surface finish and corrosion resistance. However, the growth of bacteria on stainless steel leads to the formation of biofilms, which causes corrosion. Therefore, the antibacterial property of stainless steel is a worthy research topic. Reviews of breakthroughs in the field of corrosion resistance and antimicrobial properties are still lacking. Herein, due to the scarcity of publications on the antibacterial mechanisms and processing methods of antibacterial Cu-bearing stainless steel, we review the current state of relevant research and progress. The toxicity of Cu, corrosion resistance mechanism of stainless steel, and antibacterial mechanism and preparation method of antibacterial stainless steel are reported. In addition, alloying, surface modification and other methods are found to have limitations in balancing the toxicity and antibacterial properties of copper and the relationship between the antibacterial properties and corrosion resistance of Cu-bearing stainless steel. A new preparation method of antibacterial stainless steel associated with selective laser melting (SLM) is proposed. SLM is becoming a powerful additive manufacturing technology that can be used to manufacture customized and complex metals. The research status of SLM applied in antibacterial stainless steel preparation is described. Finally, the future research direction of Cu-bearing antibacterial stainless steel is discussed.
Copper has a long history of use as a biocidal agent. Recent studies have demonstrated that incorporating graphene into copper coatings improves their antibacterial properties. However, the implementation of copper-graphene composite coatings is currently limited by the cost and scarcity of copper, as well as the difficulty of achieving a homogeneous distribution of graphene within the copper matrix. In this study, a new approach was developed to utilize an inductively-coupled radio frequency plasma torch to spray a uniform composite coating of copper nanoparticles and graphene nanoflakes (GNFs) onto a metal substrate. The resulting composite coatings exhibit microstructural uniformity, coating splats cohesion, and GNFs retention and dispersion within the Cu matrix. Furthermore, the Cu-GNFs coatings demonstrated strong antibacterial properties, with a 99% reduction of Escherichia coli bacteria within 1 hour.
Recently, the development of materials with antimicrobial properties has become a challenge under scrutiny. The incorporation of copper nanoparticles (NpCu) into a chitosan matrix appears to represent a viable strategy to contain the particles and prevent their oxidation. Regarding the physical properties, the nanocomposite films (CHCu) showed a decrease in the elongation at break (5 %) and an increase in the tensile strength of 10 % concerning chitosan films (control). They also showed solubility values lower than 5 % while the swelling diminished by 50 %, on average. The dynamical mechanical analysis (DMA) of nanocomposites revealed two thermal events located at 113° and 178 °C, which matched the glass transitions of the CH-enriched phase and nanoparticles-enriched phase, respectively. In addition, the thermogravimetric analysis (TGA) detected a greater stability of the nanocomposites. Chitosan films and the NpCu-loaded nanocomposites demonstrated excellent antibacterial capacity against Gram-negative and Gram-positive bacteria, proved through diffusion disc, zeta potential, and ATR-FTIR techniques. Additionally, the penetration of individual NpCu particles into bacterial cells and the leakage of cell content were verified by TEM. The mechanism of the antibacterial activity of the nanocomposites involved the interaction of chitosan with the bacterial outer membrane or cell wall and the diffusion of the NpCu through the cells. These materials could be applied in diverse fields of biology, medicine, or food packaging.
Antibacterial elements and non‐contact heating abilities have been proven effective for antibacterial and antibiofilm activities, but it remains a challenge to integrate both within one material. Herein, assisted by the high‐entropy effect, FeNiTiCrMnCux high‐entropy alloy nanoparticles (HEA‐NPs) with excellent photothermal heating properties for boosting antibacterial and antibiofilm performances are synthesized. Benefitting from the synergetic effect of copper ions released and thermal damage by the HEA‐NPs, more reactive oxygen species (ROS) are generated, leading to the rupture of the cell membranes and the eradication of the biofilms. As a result, the antibiofilm efficiency (400 µg mL⁻¹) of the mostly optimized FeNiTiCrMnCu1.0 HEA‐NPs in the marine nutrient medium, which is the worst‐case scenario for the antimicrobial material, can be improved from 81% to 97.4% under 30 min solar irradiation (1 sun). The present study demonstrates a new strategy for effectively treating marine microorganisms that cause biofouling and microbial corrosion using HEA‐NPs with photothermal heating characteristics as an antibacterial auxiliary.
The ability of bacteria to maintain homeostasis of the essential-but-toxic “Janus”-faced element copper is important for their survival in many natural environments but also in case of pathogenic bacteria in their respective host. The most important contributors to copper homeostasis have been identified in the last decades and comprise P IB1 -type ATPases, periplasmic copper- and oxygen-dependent copper oxidases, transenvelope efflux systems, and glutathione; however, it is not known how all these players interact.
Regeneration of biological tissues in medicine is challenging, and 3D bioprinting offers an innovative way to create functional multicellular tissues. One common way in bioprinting is bioink which is one type of the cell-loaded hydrogel. For clinical application, however, the bioprinting still suffers from satisfactory performance, e.g. in vascularization, effective antibacterial, immunomodulation and regulation of collagen deposition. Many studies have incorporated different bioactive materials into the 3D printed scaffolds to optimize the bioprinting. Here, we review a variety of additives added to the 3D bioprinting hydrogel. The underlying mechanisms and methodology for biological regeneration are important and will provide useful basis for future research.
With the widespread dispersal of pathogens, toxins and all sorts of harmful chemicals throughout the globe, the demand for suitable cleaners, hand sanitisers and surface disinfectants are increasing day by day. Most of the conventional sanitisers are alkali-based, like the soap cakes, liquid soaps, and detergents; or alcohol-based liquids, gels, or sprays. The recent pandemic situation led to an unprecedented rise in the production and use (as well as overuse) of such disinfectants. But all of them have certain detrimental effects on human health and also on the environment. Since reducing the use of disinfectants is not possible in the present scenario, the only solution is to find out a better alternative that can effectively clean a surface without causing any harm. The natural clays, owing to their unique physical and chemical properties, can remove from a surface a wide variety of viruses, bacteria, grease and dirt. In some cases, clay minerals assist in the bactericidal actions of cations like Fe 2+ , Cu + detrimental effect on human health instead of damaging the skin, the clay-based disinfectants may contribute to skin nourishment. Furthermore, clays are readily available everywhere, and their purification processes are also simple and less expensive. This makes them suitable for large-scale production of low-cost skin sanitisers and surface disinfectants, thus helping the developing economies to meet the challenges of the ever-increasing demands for these products. This contribution explains the correlation between the internal structures, chemical compositions and properties of clay minerals that make them suitable as cleaners and disinfectants, and discusses the present situation and future prospects of the clay-based sanitisers.
This review discussed the relationship among copper, human, and bacteria. Copper plays an important role in human immunity. Copper can boost human immune defense reactions at recommended intake level. The content mainly focused on copper antibacterial activity and copper antibacterial mechanisms. Conclusions stated that copper antibacterial activity is affected by copper homeostasis mechanisms in bacteria, adhesion, humidity, strain specificity, and manufacturing methods of antibacterial agents. For the preparation of particle antibacterial agents and surface antibacterial agents, this review discussed several manufacturing methods, such as sol-gel, cold spray, and biosynthesis belonging to chemical synthesis, physical synthesis, and biological synthesis, respectively. Sol-gel method contributes to the preparation of particle agents and surface agents. Cold spray technique is utilized in synthesis of surface copper agent. Biosynthesis is a novel technology which can be applied in nanoparticle agent preparation.
The remarkable link between the strength and location of the Localized Surface Plasmon Resonance (LSPR) peak and the size, shape, and density of Cu NPs has been validated by numerous investigations on the optical properties of copper NPs. The prospect of attaining Cu NPs with tunable LSPR peak may be useful for developing catalysts, biosensors, optoelectronic devices, optical devices, etc. The diversity, complexity and heterogeneity of cancer and bacteria-causing diseases have placed them among the most disheartening infections that threaten the health of humans for so many years. Investigations on copper oxide's optical, anticancer, and antibacterial properties have been carried out on a number of occasions due to their fascinating properties, which have been discovered as a potential therapeutic agent for the treatment of both cancer and bacteria-causing illnesses. Despite these established investigations, little review research has been done on the antibacterial and anticancer properties of copper NPs and their oxides. The optical properties of copper NPs and their oxides are not known to have any recorded review information. The optical characteristics of copper NPs and their efficacy in treating cancer and bacterial infections are highlighted in this review as a result. The mechanism of action of CuO NPson cancer strains and bacterial strains, challenges, and recommendations in the clinical application of copper nanomedicine were also highlighted. The evaluated studies developed copper oxide nanoparticles with enhanced optical characteristics; however, the methods and conditions used in each study's synthesis varied from study to study. Outstanding anticancer and antibacterial properties were exhibited by the studied copper oxide nanoparticles. It is clear that most approaches are still unable to bring copper nanosystems loaded with anticancer and antibacterial agents to the clinic; thus, additional work must be done to solve the major issues of the cancer epidemic and antibiotic resistance.
Contaminated surfaces are a major source of nosocomial infection. To reduce microbial bioburden and surface‐based transmission of infectious disease, the use of antibacterial and self‐sanitizing surfaces, such as copper (Cu), is being explored in clinical settings. Cu has long been known to have antimicrobial activity. However, Gram‐positive microorganisms, a class that includes pathogens commonly responsible for hospital‐acquired infection such as Staphylococcus aureus and Clostridioides difficile, are more resilient to its biocidal effect. Inspired by inherently bactericidal nanostructured surfaces found in nature, an improved Cu coating is developed, engineered to contain nanoscale surface features and thus increase its antibacterial activity against a broader range of organisms. In addition, a new method is established for facilitating the rapid and continuous release of biocidal metal ions from the coating, through incorporation of an antibacterial metal salt (ZnCl2) with a lower reduction potential than Cu. Electrophoretic deposition (EPD) is used to fabricate these coatings, which serves as a low‐cost and scalable route for modifying existing conductive surfaces with complex shape. By tuning both the surface morphology and chemistry, a nanocomposite Cu coating is created that decreases the microbial bioburden of Gram‐positive S. aureus by 94% compared to unmodified Cu. Antimicrobial copper (Cu) products are being deployed in clinical settings to decrease microbial bioburden and prevent surface‐based transmission of infectious disease. However, Gram‐positive bacteria demonstrate increased resistance to Cu's biocidal effects. To improve Cu's antibacterial efficacy against Gram‐positive bacteria, a hydrophobic Cu coating was developed with cytotoxic nanotopography that facilitates the rapid and continuous release of biocidal metal ions.
"This study targeted at providing a solution to overcome antimicrobial resistance through new pyridine complexes represented with the general formula [ML2Cl2] (L1: 2-amino-3-methylpyridine; L2: 2,6-diaminopyridine; M: Ni(II), Cu(II), Co(II)). The structures of the synthesized complexes were characterized via FT-IR, 1H-NMR and 13C-NMR techniques. These complexes were used for obtaining hybrid microfibers via electrospinning of cellulose acetate modified with them. The microfibers were characterized via FT-IR spectroscopy and their FE-SEM micrographs were used to study their morphologies and determine their diameters. Thermal properties of the fibers were investigated by a TG/DTA combined system. The antibacterial properties of the complexes and fibers were investigated against representative gram-positive and gram-negative bacterial strains by disc diffusion and broth microdilution tests, as well as by the JIS L 1902: 2008 testing method for antibacterial activity of textiles. The complexes and the hybrid microfibers were observed to have considerable antibacterial activity."
Cryptocaryon irritans infection could cause huge economic losses to the marine fish industry. Due to the lack of targeted anti-parasitic drugs, CuSO4 is widely used in the prevention and control of parasitic diseases in aquaculture. C. irritans tomonts are “cyst like, reproductive stage” of the parasites life cycle that is highly resistant to different compounds and drugs. In this study, we explored the effects of CuSO4 on the C. irritans tomonts, incubation rate, morphological difference and transcriptome changes. The results showed that the tomonts treated with CuSO4 had a thicker cyst wall than the control group. Ultrastructural analysis of C. irritans tomonts exhibited less encapsulated content after CuSO4 treatment, while tomonts organelle was abundant in the control group. The hatching rate of tomonts treated with CuSO4 (10 mg/L) was lower (25.92–40.73%) than that of tomonts without treatment with chemical drugs (80.77–95.45%). Differentially expressed genes (DEGs) analysis revealed that 223 DEGs including 160 DEGs up-regulated and 63 DEGs down-regulated genes were identified. In GO analysis, relatively more upregulated DEGs were annotated into growth, reproduction and reproductive process, while down-regulated DEGs were mainly annotated into biological adhesion, immune system process, and supramolecular complex. In the KEGG enrichment analysis, Taste transduction (ko04742), Circadian entrainment (ko04713), Vascular smooth muscle contraction (ko04270) and Platelet activation (ko04611) were the top 4 pathways with the highest degree of enrichment. In addition, IP3R, AC, PKG, MLCP and MPase genes involved in regulating calcium flow play an important role in these pathways. Taken together, our results indicate that CuSO4 may affect the C. irritans tomonts by influencing the calcium flow.
Lignin is a natural polymer produced in huge amounts by the paper industry. Innovative applications of lignin, especially in agriculture, represent a valuable way to develop a more sustainable economy. Its antioxidant and antimicrobial properties, combined with its biodegradability, make it particularly attractive for the development of plant protection products. Copper is an element that has long been used as a pesticide in agriculture. Despite its recognized antimicrobial activity, the concerns derived from its negative environmental impact is forcing research to move toward the development of more effective and sustainable copper‐based pesticides. Here a simple and sustainable way of synthesizing a new hybrid material composed of Cu2O nanocrystals embedded into lignin, named Lignin@Cu2O is presented. The formation of cuprite nanocrystals leaves the biopolymer intact, as evidenced by infrared spectroscopy, gel permeation chromatography, and Pyrolysis‐GC analysis. The combined activity of lignin and cuprite make Lignin@Cu2O effective against Listeria monocytogenes and Rhizoctonia solani at low copper dosage, as evidenced by in vitro and in vivo tests conducted on tomato plants. The reaction between a basic solution of lignin and copper sulfate leads to the formation of the hybrid material Lignin@Cu2O, where cuprite nanocrystals are embedded into the biopolymeric framework. The material is an effective antimicrobial agent at low copper dosage against several pathogens, such as Listeria monocytogenes and Rhizoctonia solani, as demonstrated by in vitro and in vivo tests.
Salmonella enteritidis is an important food-borne pathogen. The use of antibiotics is a serious threat to animal and human health, owing to the existence of resistant strains and drug residues. Lactic acid bacteria, as a new alternative to antibiotics, has attracted much attention. In this study, we investigated the antibacterial potential and underlying mechanism of Lactobacillus rhamnosus SQ511 against S. enteritidis ATCC13076. The results revealed that L. rhamnosus SQ511 significantly inhibited S. enteritidis ATCC13076 growth or even caused death. Laser confocal microscopic imaging revealed that the cell-free supernatant (CFS) of L. rhamnosus SQ511 elevated the reactive oxygen species level and bacterial membrane depolarization in S. enteritidis ATCC13076, leading to cell death. Furthermore, L. rhamnosus SQ511 CFS had severely deleterious effects on S. enteritidis ATCC13076, causing membrane destruction and the release of cellular materials. In addition, L. rhamnosus SQ511 CFS significantly reduced the expression of virulence, motility, adhesion, and invasion genes in S. enteritidis ATCC13076 (P < 0.05), and considerably inhibited motility and biofilm formation capacity (P < 0.05). Thus, antimicrobial compounds produced by L. rhamnosus SQ511 strongly inhibited S. enteritidis growth, mobility, biofilm formation, membrane disruption, and reactive oxygen species generation, and regulated virulence-related gene expressions, presenting promising applications as a probiotic agent.
The transmission of bacterial infections through contaminated surfaces is nowadays an increasing source of concern, also related to the current pandemic situation. Functional materials that prevent the adhesion of microorganisms and/or induce their eradication thus avoiding fomite transmission are highly needed. In this work, a highly antimicrobial hybrid with sensorial capability is developed to be further applied as interactive high traffic surface coatings. The nanocomposite is composed of polyvinylidene fluoride (PVDF), a highly stable fluorinated polymer, incorporating copper core‐shell nanowires (NWs). The NWs comprised of copper and shelled with silver is highly antimicrobial, inducing a full kill effect against Escherichia coli and Staphylococcus epidermidis strains but biocompatible towards mammalian cells at concentrations below 0.5 mg mL−1. Further NWs incorporation on PVDF matrix retains its antimicrobial activity reducing in 6.5 logs the E. coli and 4.5 logs the S. epidermidis. NW/PVDF composites demonstrate suitable mechanical and electrical characteristics for the development of capacitive sensing surfaces, allowing for the fabrication of an antimicrobial capacitive touch sensing matrix for interactive surfaces. Multifunctional polymer composites are developed for high‐traffic touch surfaces, allowing them to manage viruses or bacteria transmission and, simultaneously, work as interactive surfaces. The antimicrobial capability is provided using synthesized core/shell metallic nanowires which are then embedded into polyvinylidene fluoride polymer, with a high dielectric response. The antimicrobial and sensorial capability is demonstrated in an interactive touch sensing surface.
Cryptocaryonosis, caused by the ciliate parasite Cryptocaryon irritans, results in large economic losses in large yellow croaker (Larimichthys crocea) culture. In order to explore the effect of copper plates on C. irritans tomonts, incubation rate, morphological characteristics, copper concentration, and transcriptome changes were studied. After copper plate treatment for 6 h, the tomonts showed erosion in the internal structure and the tomonts wall exhibited reduced transparency. Compared with the control group, the hatching rate of tomonts in the treatment group was significantly lower. Copper concentrations of tomonts in the treatment group was 340.67 ± 0.94 mg/kg, while the copper value in the control group was 22.40 ± 0.91 mg/kg. Transcriptome analysis revealed that 21 GO terms were significantly enriched by differential expression genes (DEGs). Among them, the regulation of cellular respiration and protein-containing complexes were highly enriched (q-value<0.001). The results of KEGG analysis showed that the ribosome pathway and the systemic lupus erythematosus pathway were the most significantly enriched pathways. In addition, most of the annotated DEGs on these two pathways were down-regulated indicating the killing effect was mainly mediated by ribosomal proteins, histones, and small nuclear ribonucleoproteins.
This study investigates the interaction between Escherichia coli（E. coli） and various surface states of Cu. Pure Cu was first immersed in ultrapure water for 24 h at 298 K and then oxidized at 673 and 1273 K. Subsequently, its surface chemical states were characterized using X-ray photoelectron spectroscopy （XPS）. The oxidized specimens were immersed in both bacteria-free and bacteria-containing solutions, and the release of Cu ions from each specimen was evaluated. The specimens that existed mainly as Cu＋ on the surface were found to promote the elution of Cu ions because of the presence of E. coli in the immersion solution. In contrast, the specimen that existed mainly as Cu2＋ showed no changes in Cu release in the presence of bacteria. XPS analyses conducted before and after immersion in bacteria-free and bacteria-containing solutions showed that the presence of E. coli inhibited the generation of Cu2＋ on the surface and promoted Cu ion elution. This study proposes that the specific corrosion behavior of Cu in response to bacteria is beneficial for developing its antibacterial properties.
Escherichia coli O157:H7 is a serious pathogen causing haemorrhagic colitis. It has been responsible for several large-scale outbreaks in recent years. E. coli O157:H7 is able to survive in a range of environments, under various conditions. The risk of infection from contaminated surfaces is recognised, especially due to the low infectious dose required. In this study, a high concentration (107 cells) of E. coli O157 was placed onto different metals and survival time measured. Results showed E. coli O157 to survive for over 28 days at both refrigeration and room temperatures on stainless steel. Copper, in contrast, has strong antibacterial properties (no bacteria can be recovered after only 90 min exposure at 20 °C, increasing to 270 min at 4 °C) but its poor corrosion resistance and durability make it unsuitable for use as a surface material. Other copper-containing alloys, such as copper nickels and copper silvers, have improved durability and anticorrosion properties and greatly reduce bacterial survival times at these two temperatures (after 120 min at 20 °C and 360 min at 4 °C, no E. coli could be detected on a copper nickel with a 73% copper content). Use of a surface material with antibacterial properties could aid in preventing cross-contamination events in food processing and domestic environments, if standard hygiene measures fail.
The acquisition of microbes with the subsequent development of an infection while hospitalized continues to challenge healthcare worldwide. The CDC estimates the overall risk, mortality and cost to the USA to be ~5%, 100,000 deaths and ~45 billion additional dollars; rates for Medical Intensive Care Units (MICU) are higher where the risk often exceeds 25%. At issue is whether reducing the microbial burden of the environment can lead to an effective method to limit the risk of acquiring an infection while hospitalized.
Aims:
As copper has been previously suggested as an antimicrobial surface, we tested the effectiveness of copper as an antifungal surface which could be used in air-conditioning systems as an alternative to aluminium.
Methods and results:
Coupons of copper (C11000) and aluminium were inoculated with fungal isolates (Aspergillus spp., Fusarium spp., Penicillium chrysogenum and Candida albicans) for various time periods. Culture on potato dextrose agar and an in situ viability assay using the fluorochrome FUN-1 were used to determine whether spores had survived. The results showed increased die off of fungal isolates tested compared to aluminium. In addition, copper also prevented the germination of spores present, thereby reducing the risk of the release of spores.
Conclusions:
Copper offered an antifungal surface and prevented subsequent germination of spores present. FUN-1 demonstrated that fungal spores entered into a viable but not culturable (VBNC) state on copper indicating the importance of using such methods when assessing the effect of an antifungal as culture alone may give false results.
Significance and impact of study:
Copper offers a valuable alternative to aluminium which could be used in air-conditioning systems in buildings, particularly in hospital environments where patients are more susceptible to fungal infections.
Contaminated touch surfaces have been implicated in the spread of hospital-acquired infections, and the use of biocidal surfaces could help to reduce this cross-contamination. In a previous study we reported the death of aqueous inocula of pathogenic Enterococcus faecalis or Enterococcus faecium isolates, simulating fomite surface contamination, in 1 h on copper alloys, compared to survival for months on stainless steel. In our current study we observed an even faster kill of over a 6-log reduction of viable enterococci in less than 10 min on copper alloys with a "dry" inoculum equivalent to touch contamination. We investigated the effect of copper(I) and copper(II) chelation and the quenching of reactive oxygen species on cell viability assessed by culture and their effects on genomic DNA, membrane potential, and respiration in situ on metal surfaces. We propose that copper surface toxicity for enterococci involves the direct or indirect action of released copper ionic species and the generation of superoxide, resulting in arrested respiration and DNA breakdown as the first stages of cell death. The generation of hydroxyl radicals by the Fenton reaction does not appear to be the dominant instrument of DNA damage. The bacterial membrane potential is unaffected in the early stages of wet and dry surface contact, suggesting that the membrane is not compromised until after cell death. These results also highlight the importance of correct surface cleaning protocols to perpetuate copper ion release and prevent the chelation of ions by contaminants, which could reduce the efficacy of the surface.
Biofilms are slimy aggregates of microbes that are likely responsible for many chronic infections as well as for contamination
of clinical and industrial environments. Pseudomonas aeruginosa is a prevalent hospital pathogen that is well known for its ability to form biofilms that are recalcitrant to many different
antimicrobial treatments. We have devised a high-throughput method for testing combinations of antimicrobials for synergistic
activity against biofilms, including those formed by P. aeruginosa. This approach was used to look for changes in biofilm susceptibility to various biocides when these agents were combined
with metal ions. This process identified that Cu2+ works synergistically with quaternary ammonium compounds (QACs; specifically benzalkonium chloride, cetalkonium chloride,
cetylpyridinium chloride, myristalkonium chloride, and Polycide) to kill P. aeruginosa biofilms. In some cases, adding Cu2+ to QACs resulted in a 128-fold decrease in the biofilm minimum bactericidal concentration compared to that for single-agent
treatments. In combination, these agents retained broad-spectrum antimicrobial activity that also eradicated biofilms of Escherichia coli, Staphylococcus aureus, Salmonella enterica serovar Cholerasuis, and Pseudomonas fluorescens. To investigate the mechanism of action, isothermal titration calorimetry was used to show that Cu2+ and QACs do not interact in aqueous solutions, suggesting that each agent exerts microbiological toxicity through independent
biochemical routes. Additionally, Cu2+ and QACs, both alone and in combination, reduced the activity of nitrate reductases, which are enzymes that are important
for normal biofilm growth. Collectively, the results of this study indicate that Cu2+ and QACs are effective combinations of antimicrobials that may be used to kill bacterial biofilms.
Copper is both an essential nutrient and a toxic element able to catalyze free radicals formation which damage lipids and proteins. Although the available copper redox species in aerobic environment is Cu(II), proteins that participate in metal homeostasis use Cu(I). With isolated Escherichia coli membranes, we have previously shown that electron flow through the respiratory chain promotes cupric ions reduction by NADH dehydrogenase-2 and quinones. Here, we determined Cu(II)-reductase activity by whole cells using strains deficient in these respiratory chain components. Measurements were done by the appearance of Cu(I) in the supernatants of cells exposed to sub-lethal Cu(II) concentrations. In the absence of quinones, the Cu(II)-reduction rate decreased ~70% in respect to the wild-type strain, while this diminution was about 85% in a strain lacking both NDH-2 and quinones. The decrease was ~10% in the absence of only NDH-2. In addition, we observed that quinone deficient strains failed to grow in media containing either excess or deficiency of copper, as we have described for NDH-2 deficient mutants. Thus, the Cu(II)-reduction by E. coli intact cells is mainly due to quinones and to a lesser extent to NDH-2, in a quinone-independent way. To our knowledge, this is the first in vivo demonstration of the involvement of E. coli respiratory components in the Cu(II)-reductase activity which contributes to the metal homeostasis.
Metallic copper surfaces have strong antimicrobial properties and kill bacteria, such as Escherichia coli, within minutes in a process called contact killing. These bacteria are exposed to acute copper stress under dry conditions which is different from chronic copper stress in growing liquid cultures. Currently, the physiological changes of E. coli during the acute contact killing process are largely unknown. Here, a label-free, quantitative proteomic approach was employed to identify the differential proteome profiles of E. coli cells after sub-lethal and lethal exposure to dry metallic copper. Of the 509 proteins identified, 110 proteins were differentially expressed after sub-lethal exposure, whereas 136 proteins had significant differences in their abundance levels after lethal exposure to copper compared to unexposed cells. A total of 210 proteins were identified only in copper-responsive proteomes. Copper surface stress coincided with increased abundance of proteins involved in secondary metabolite biosynthesis, transport and catabolism, including efflux proteins and multidrug resistance proteins. Proteins involved in translation, ribosomal structure and biogenesis functions were down-regulated after contact to metallic copper. The set of changes invoked by copper surface-exposure was diverse without a clear connection to copper ion stress but was different from that caused by exposure to stainless steel. Oxidative posttranslational modifications of proteins were observed in cells exposed to copper but also from stainless steel surfaces. However, proteins from copper stressed cells exhibited a higher degree of oxidative proline and threonine modifications.
Bacteria, yeasts, and viruses are rapidly killed on metallic copper surfaces, and the term "contact killing" has been coined for this process. While the phenomenon was already known in ancient times, it is currently receiving renewed attention. This is due to the potential use of copper as an antibacterial material in health care settings. Contact killing was observed to take place at a rate of at least 7 to 8 logs per hour, and no live microorganisms were generally recovered from copper surfaces after prolonged incubation. The antimicrobial activity of copper and copper alloys is now well established, and copper has recently been registered at the U.S. Environmental Protection Agency as the first solid antimicrobial material. In several clinical studies, copper has been evaluated for use on touch surfaces, such as door handles, bathroom fixtures, or bed rails, in attempts to curb nosocomial infections. In connection to these new applications of copper, it is important to understand the mechanism of contact killing since it may bear on central issues, such as the possibility of the emergence and spread of resistant organisms, cleaning procedures, and questions of material and object engineering. Recent work has shed light on mechanistic aspects of contact killing. These findings will be reviewed here and juxtaposed with the toxicity mechanisms of ionic copper. The merit of copper as a hygienic material in hospitals and related settings will also be discussed.
Metallic copper surfaces rapidly and efficiently kill bacteria. Cells exposed to copper surfaces accumulated large amounts
of copper ions, and this copper uptake was faster from dry copper than from moist copper. Cells suffered extensive membrane
damage within minutes of exposure to dry copper. Further, cells removed from copper showed loss of cell integrity. Acute contact
with metallic copper surfaces did not result in increased mutation rates or DNA lesions. These findings are important first
steps for revealing the molecular sensitive targets in cells lethally challenged by exposure to copper surfaces and provide
a scientific explanation for the use of copper surfaces as antimicrobial agents for supporting public hygiene.
Surfaces made of copper or its alloys have strong antimicrobial properties against a wide variety of microorganisms. However,
the molecular mode of action responsible for the antimicrobial efficacy of metallic copper is not known. Here, we show that
dry copper surfaces inactivate Candida albicans and Saccharomyces cerevisiae within minutes in a process called contact-mediated killing. Cellular copper ion homeostasis systems influenced the kinetics
of contact-mediated killing in both organisms. Deregulated copper ion uptake through a hyperactive S. cerevisiae Ctr1p (ScCtr1p) copper uptake transporter in Saccharomyces resulted in faster inactivation of mutant cells than of wild-type cells. Similarly, lack of the C. albicans Crp1p (CaCrp1p) copper-efflux P-type ATPase or the metallothionein CaCup1p caused more-rapid killing of Candida mutant cells than of wild-type cells. Candida and Saccharomyces took up large quantities of copper ions as soon as they were in contact with copper surfaces, as indicated by inductively
coupled plasma mass spectroscopy (ICP-MS) analysis and by the intracellular copper ion-reporting dye coppersensor-1. Exposure
to metallic copper did not cause lethality through genotoxicity, deleterious action on a cell's genetic material, as indicated
by a mutation assay with Saccharomyces. Instead, toxicity mediated by metallic copper surfaces targeted membranes in both yeast species. With the use of Live/Dead
staining, onset of rapid and extensive cytoplasmic membrane damage was observed in cells from copper surfaces. Fluorescence
microscopy using the indicator dye DiSBaC2(3) indicated that cell membranes were depolarized. Also, during contact-mediated killing, vacuoles first became enlarged
and then disappeared from the cells. Lastly, in metallic copper-stressed yeasts, oxidative stress in the cytoplasm and in
mitochondria was elevated.
The increasing incidence of nosocomial infections caused by glycopeptide-resistant enterococci is a global concern. Enterococcal species are also difficult to eradicate with existing cleaning regimens; they can survive for long periods on surfaces, thus contributing to cases of reinfection and spread of antibiotic-resistant strains. We have investigated the potential use of copper alloys as bactericidal surfaces. Clinical isolates of vancomycin-resistant Enterococcus faecalis and Enterococcus faecium were inoculated onto copper alloy and stainless steel surfaces. Samples were assessed for the presence of viable cells by conventional culture, detection of actively respiring cells, and assessment of cell membrane integrity. Both species survived for up to several weeks on stainless steel. However, no viable cells were detected on any alloys following exposure for 1 h at an inoculum concentration of <or=10(4) CFU/cm(2). Analysis of genomic and plasmid DNA from bacterial cells recovered from metal surfaces indicates substantial disintegration of the DNA following exposure to copper surfaces that is not evident in cells recovered from stainless steel. The DNA fragmentation is so extensive, and coupled with the rapid cell death which occurs on copper surfaces, that it suggests that mutation is less likely to occur. It is therefore highly unlikely that genetic information can be transferred to receptive organisms recontaminating the same area. A combination of effective cleaning regimens and contact surfaces containing copper could be useful not only to prevent the spread of viable pathogenic enterococci but also to mitigate against the occurrence of potential resistance to copper, biocides, or antibiotics and the spread of genetic determinants of resistance to other species.
The ability of many bacteria to adhere to surfaces and to form biofilms has major implications in a variety of industries including the food industry, where biofilms create a persistent source of contamination. The formation of a biofilm is determined not only by the nature of the attachment surface, but also by the characteristics of the bacterial cell and by environmental factors. This review focuses on the features of the bacterial cell surface such as flagella, surface appendages and polysaccharides that play a role in this process, in particular for bacteria linked to food-processing environments. In addition, some aspects of the attachment surface, biofilm control and eradication will be highlighted.
A meat factory commensal bacterium, Acinetobacter calcoaceticus, affected the spatial distribution of Escherichia coli O157:H7 surface colonization. The biovolume of E. coli O157:H7 was 400-fold higher (1.2 x 10(6) microm(3)) in a dynamic cocultured biofilm than in a monoculture (3.0 x 10(3) microm(3)), and E. coli O157:H7 colonized spaces between A. calcoaceticus cell clusters.
Bacteria are rapidly killed on copper surfaces. However, the mechanism of this process remains unclear. Using Enterococcus hirae, the effect of inactivation of copper homeostatic genes and of medium compositions on survival and copper dissolution was
tested. The results support a role for dissolved copper ions in killing.
Enterohemorrhagic Escherichia coli O157:H7 is a major food-borne pathogen causing severe disease in humans worldwide. Healthy cattle are a reservoir of E. coli O157:H7 and bovine food products and fresh produce contaminated with bovine waste are the most common sources for disease outbreaks in the United States. E. coli O157:H7 also survives well in the environment. The ability to cause human disease, colonize the bovine gastrointestinal tract, and survive in the environment, requires that E. coli O157:H7 adapt to a wide variety of conditions. Three major virulence factors of E. coli O157:H7 have been identified including Shiga toxins, a pathogenicity island called the locus of enterocyte effacement, and an F-like plasmid, pO157. Among these virulence factors, the role of the pO157 is least understood. This review provides a board overview of E. coli O157:H7 with an emphasis on the pO157.
Metallic copper alloys have recently attracted attention as a new antimicrobial weapon for areas where surface hygiene is paramount. Currently it is not understood on a molecular level how metallic copper kills microbes, but previous studies have demonstrated that a wide variety of bacteria, including Escherichia coli, Staphylococcus aureus, and Clostridium difficile, are inactivated within minutes or a few hours of exposure. In this study, we show that bacteria isolated from copper alloy coins comprise strains that are especially resistant against the toxic properties exerted by dry metallic copper surfaces. The most resistant of 294 isolates were Gram-positive staphylococci and micrococci, Kocuria palustris, and Brachybacterium conglomeratum but also included the proteobacterial species Sphingomonas panni and Pseudomonas oleovorans. Cells of some of these bacterial strains survived on copper surfaces for 48 h or more. Remarkably, when these dry-surface-resistant strains were exposed to moist copper surfaces, resistance levels were close to those of control strains and MICs for copper ions were at or below control strain levels. This suggests that mechanisms conferring resistance against dry metallic copper surfaces in these newly isolated bacterial strains are different from well-characterized copper ion detoxification systems. Furthermore, staphylococci on coins did not exhibit increased levels of resistance to antibiotics, arguing against coselection with copper surface resistance traits.
To compare silver and copper, metals with known antimicrobial properties, by evaluating the effects of temperature and humidity on efficacy by challenging with methicillin resistant Staphylococcus aureus (MRSA).
Using standard methodology described in a globally used Japanese Industrial Standard, JIS Z 2801, a silver ion-containing material exhibited >5 log reduction in MRSA viability after 24 h at >90% relative humidity (RH) at 20 degrees C and 35 degrees C but only a <0.3 log at approximately 22% RH and 20 degrees C and no reduction at approximately 22% RH and 35 degrees C. Copper alloys demonstrated >5 log reductions under all test conditions.
While the high humidity (>90% RH) and high temperature (35 degrees C) utilized in JIS Z 2801 produce measurable efficacy in a silver ion-containing material, it showed no significant response at lower temperature and humidity levels typical of indoor environments.
The high efficacy levels displayed by the copper alloys, at temperature and humidity levels typical of indoor environments, compared to the low efficacy of the silver ion-containing material under the same conditions, favours the use of copper alloys as antimicrobial materials in indoor environments such as hospitals.
The ability of metal ions to damage DNA and cause mutagenesis has been analyzed with reversion and forward mutation assays using single-stranded DNA templates. We previously reported that incubation of phi X174 am3 DNA with Fe2+ in vitro results in mutagenesis when the treated DNA is transfected into Escherichia coli spheroplasts (Loeb, L. A., James, E. A., Waltersdorph, A. M., and Klebanoff, S. J. (1988) Proc. Natl. Acad. Sci. U.S.A. 85, 3918-3922, 1988). We now extend these studies to other metal ions. Of the metal ions tested, copper ions were the most mutagenic; the frequency of mutants produced was equal to or greater than that produced by Fe2+. Mutagenesis by Cu+ was diminished by catalase, mannitol, and superoxide dismutase suggesting the involvement of H2O2, hydroxyl ions, and superoxide, respectively. However, the findings that Cu+ and Cu2+ are nearly equally mutagenic and that the mutagenic activities are not completely inhibited by oxygen free radical scavengers make it unlikely that the mechanism for mutagenesis is simply the production of hydroxyl free radicals. The spectra of mutations produced by either copper ion using the lacZ gene as a target are very similar and differ from those reported with other agents. The predominant mutagenic sequence changes are single-base substitutions, the most frequent being replacement of a template C by a T. This transition presumably results from mispairing of an altered C with deoxyadenosine. Copper-induced mutations are not randomly distributed. Instead, they are found predominantly in clusters suggesting direct interaction of copper ions with specific nucleotide sequences in DNA. Evidence is considered that the high frequency of C----T transitions may be a common manifestation of DNA damage by oxygen radicals.
The site specificity of metallic ion binding in Escherichia coli K-12 lipopolysaccharide was assessed by collecting high-resolution phosphorus nuclear magnetic resonance spectra in the presence of manganese, a paramagnetic divalent cation. This technique revealed high-affinity interactions between the cation and all of the lipopolysaccharide phosphoryl groups. To ascertain whether the carboxyl groups of 2-keto-3-deoxyoctonate contributed to the metal cation binding, lipopolysaccharide was chemically modified using a glycine ethyl ester - carbodiimide reaction. Of the three available carboxyl groups, only one was neutralized by the exogenously added ligand; the others appeared to be cross-linked within the molecule. By analogy, only one carboxyl group should be freely available for binding metallic ions, while the others are probably neutralized by the close proximity of endogenous amino substituents. Although high-resolution phosphorus nuclear magnetic resonance showed that an intermolecular conformational change had occurred after the carboxyl groups were neutralized, titration with manganese revealed no differences in the apparent strength of the interactions between the cation and the phosphoryl groups. Together, these data suggest that the high affinity of lipopolysaccharide for divalent metallic ions can be attributed primarily to the phosphoryl substituents and not free carboxyl groups.
Although flow cytometry has been used to study antibiotic effects on bacterial membrane potential (MP) and membrane permeability, flow cytometric results are not always well correlated to changes in bacterial counts. Using new, precise techniques, we simultaneously measured MP, membrane permeability, and particle counts of antibiotic-treated and untreated Staphylococcus aureus and Micrococcus luteus cells. MP was calculated from the ratio of red and green fluorescence of diethyloxacarbocyanine [DiOC(2)(3)]. A normalized permeability parameter was calculated from the ratio of far red fluorescence of the nucleic acid dye TO-PRO-3 and green DiOC(2)(3) fluorescence. Bacterial counts were calculated by the addition of polystyrene beads to the sample at a known concentration. Amoxicillin increased permeability within 45 min. At concentrations of <1 microg/ml, some organisms showed increased permeability but normal MP; this population disappeared after 4 h, while bacterial counts increased. At amoxicillin concentrations above 1 microg/ml, MP decreased irreversibly and the particle counts did not increase. Tetracycline and erythromycin caused smaller, dose- and time-dependent decreases in MP. Tetracycline concentrations of <1 microg/ml did not change permeability, while a tetracycline concentration of 4 microg/ml permeabilized 50% of the bacteria; 4 microg of erythromycin per ml permeabilized 20% of the bacteria. Streptomycin decreased MP substantially, with no effect on permeability; chloramphenicol did not change either permeability or MP. Erythromycin pretreatment of bacteria prevented streptomycin and amoxicillin effects. Flow cytometry provides a sensitive means of monitoring the dynamic cellular events that occur in bacteria exposed to antibacterial agents; however, it is probably simplistic to expect that changes in a single cellular parameter will suffice to determine the sensitivities of all species to all drugs.
Plasmids harboring multiple antimicrobial-resistance determinants (R plasmids) were transferred in simulated natural microenvironments from various bacterial pathogens of human, animal, or fish origin to susceptible strains isolated from a different ecological niche. R plasmids in a strain of the human pathogen Vibrio cholerae O1 E1 Tor and a bovine Escherichia coli strain were conjugated to a susceptible strain of the fish pathogenic bacterium Aeromonas salmonicida subsp. salmonicida in marine water. Conjugations of R plasmids between a resistant bovine pathogenic E. coli strain and a susceptible E. coli strain of human origin were performed on a hand towel contaminated with milk from a cow with mastitis. A similar conjugation event between a resistant porcine pathogenic E. coli strain of human origin was studied in minced meat on a cutting board. Conjugation of R plasmids between a resistant strain of the fish pathogenic bacterium A. salmonicida subsp. salmonicida and a susceptible E. coli strain of human origin was performed in raw salmon on a cutting board. R plasmids in a strain of A. salmonicida subsp. salmonicida and a human pathogenic E. coli strain were conjugated to a susceptible porcine E. coli strain in porcine feces. Transfer of the different R plasmids was confirmed by plasmid profile analyses and determination of the resistance pattern of the transconjugants. The different R plasmids were transferred equally well under simulated natural conditions and under controlled laboratory conditions, with median conjugation frequencies ranging from 3 x 10(-6) to 8 x 10(-3). The present study demonstrates that conjugation and transfer of R plasmids is a phenomenon that belongs to the environment and can occur between bacterial strains of human, animal, and fish origins that are unrelated either evolutionarily or ecologically even in the absence of antibiotics. Consequently, the contamination of the environment with bacterial pathogens resistant to antimicrobial agents is a real threat not only as a source of disease but also as a source from which R plasmids can easily spread to other pathogens of diverse origins.
Knowledge of biofilm structure and function has changed significantly in the last few years due to advances in light microscopy. One pertinent example is the use of scanning confocal laser microscopy (SCLM) to visualise corrosion pits caused by the biofilm mosaic footprint on corroding metal surfaces. Nevertheless, SCLM has some limitations as to its widespread use, including cost, inability to observe motile bacteria and eukaryotic grazers within biofilms, and difficulty to scan a curved surface. By contrast, episcopic differential interference contrast (EDIC) microscopy has provided a rapid, real time analysis of biofilms on opaque, curved, natural or man-made surfaces without the need for cover slips and oil. EDIC, coupled with epi-fluorescence (EDIC/EF), microscopy has been used successfully to visualise the 3-D biofilm structure, physiological niches, protozoal grazing and iron biomineralization, and the location of specific pathogens such as Legionella pneumophila, Campylobacter jejuni and Cryptosporidium parvum. These species were identified using gold nanoparticles or fluorophores coupled to monoclonal antibodies or 16S rRNA probes, respectively. Among its many potential uses, the EDIC technique will provide a rapid procedure to facilitate the calibration of the modern generation of biofilm-sensing electrodes.
Escherichia coli O157:H7 is a serious pathogen causing haemorrhagic colitis. It has been responsible for several large-scale outbreaks in recent years. E. coli O157:H7 is able to survive in a range of environments, under various conditions. The risk of infection from contaminated surfaces is recognised, especially due to the low infectious dose required. In this study, a high concentration (10(7) cells) of E. coli O157 was placed onto different metals and survival time measured. Results showed E. coli O157 to survive for over 28 days at both refrigeration and room temperatures on stainless steel. Copper, in contrast, has strong antibacterial properties (no bacteria can be recovered after only 90 min exposure at 20 degrees C, increasing to 270 min at 4 degrees C) but its poor corrosion resistance and durability make it unsuitable for use as a surface material. Other copper-containing alloys, such as copper nickels and copper silvers, have improved durability and anticorrosion properties and greatly reduce bacterial survival times at these two temperatures (after 120 min at 20 degrees C and 360 min at 4 degrees C, no E. coli could be detected on a copper nickel with a 73% copper content). Use of a surface material with antibacterial properties could aid in preventing cross-contamination events in food processing and domestic environments, if standard hygiene measures fail.
Epidemic meticillin-resistant Staphylococcus aureus (EMRSA) emerged in the early 1980s with EMRSA-15 and -16 being the most prevalent strains within the UK. MRSA transmission between patients is largely via the hands of healthcare workers, and contamination of the hospital environment may occur. The objective of this study was to evaluate the effectiveness of copper and brass to reduce the viability of air-dried deposits of three MRSA strains [MRSA (NCTC 10442), EMRSA-1 (NCTC 11939) and EMRSA-16 (NCTC 13143)] compared with stainless steel. MRSA and EMRSA [10(7)colony-forming units (CFU)] were inoculated on to coupons (1 cm x 1 cm) of copper, brass or stainless steel and incubated at either 22 degrees C or 4 degrees C for various time periods. Viability was determined by resuspending removed CFUs and plating out on tryptone soy agar plates in addition to staining with the respiratory indicator fluorochrome 5-cyano-2,3-ditolyl tetrazolium. On pure copper surfaces, 10(7) MRSA, EMRSA-1 and EMRSA-16 were completely killed after 45, 60 and 90 min, respectively, at 22 degrees C. In contrast, viable organisms for all three strains were detected on stainless steel (grade 304) after 72 h at 22 degrees C. At 4 degrees C, complete kill was achieved on copper for all three strains within 6 h. The results demonstrate an antimicrobial effect of copper on MRSA, EMRSA-1 and -16 in contrast to stainless steel. Consequently, the contemporary application of stainless steel in hospital environments for work surfaces and door furniture is not recommended.
Assessment of the membrane potential, intracellular pH and respiration of bacteria employing fluorescence techniquesIntroductionAll living cells require energy to grow and multiply, for synthesis of enzymes, nucleic acids, polysaccharides, and other cell components, for cell maintenance and repair of damage, for motility, and for numerous other processes. In microorganisms, there are basically two forms of metabolic energy: energy-rich phosphate bonds such as ATP, and electrochemical energy provided by ion gradients. Fermentative microorganisms, for example, can produce ATP by substrate level phosphorylation. In this process, ATP is formed by transfer of a phosphate group from a chemical compound to ADP. Additionally, many microorganisms have developed another strategy to obtain metabolic energy based on conversion of chemical, light or redox energy to energy stored in io ...
1. Oxygen is a toxic gas - an introductionto oxygen toxicity and reactive species 2. The chemistry of free radicals and related 'reactive species' 3. Antioxidant defences Endogenous and Diet Derived 4. Cellular responses to oxidative stress: adaptation, damage, repair, senescence and death 5. Measurement of reactive species 6. Reactive species can pose special problems needing special solutions. Some examples. 7. Reactive species can be useful some more examples 8. Reactive species can be poisonous: their role in toxicology 9. Reactive species and disease: fact, fiction or filibuster? 10. Ageing, nutrition, disease, and therapy: A role for antioxidants?
Homeostatic systems for essential and non-essential metals create the cellular environments in which the correct metals are acquired by metalloproteins while the incorrect ones are somehow avoided. Cyanobacteria have metal requirements often absent from other bacteria; copper in thylakoidal plastocyanin, zinc in carboxysomal carbonic anhydrase, cobalt in cobalamin but magnesium in chlorophyll, molybdenum in heterocystous nitrogenase, manganese in thylakoidal water-splitting oxygen-evolving complex. This article reviews: an intracellular trafficking pathway for inward copper supply, the sequestration of surplus zinc by metallothionein (also present in other bacteria) and the detection and export of excess cobalt. We consider the influence of homeostatic proteins on selective metal availability.
The increasing emergence of serious multidrug-resistant (MDR) Gram-negative infections has led to a new health-care crisis. These infections predominately include MDR Pseudomonas aeruginosa, extended-spectrum beta-lactamase-producing Enterobacteriaceae and MDR Acinetobacter baumannii. These organisms are present in a variety of clinical settings, but there is a distinct paucity of antibiotics to effectively treat these infections. The increasing use of broad-spectrum antibiotics and lack of good stewardship have contributed to the increase in these MDR organisms. This review focuses on the main MDR Gram-negative infections contributing to the current crisis in health care, their mechanisms of resistance and various treatment options for empiric therapy.
Escherichia coli O157 is an uncommon but serious cause of gastroenteritis. This bacterium is noteworthy because a few, but significant, number of infected people develop the haemolytic uraemic syndrome, which is the most frequent cause of acute renal failure in children in the Americas and Europe. Many infections of E coli O157 could be prevented by the more effective application of evidence-based methods, which is especially important because once an infection has been established, no therapeutic interventions are available to lessen the risk of the development of the haemolytic uraemic syndrome. This Review takes into account the evolution and geographical distibution of E coli O157 (and its close pathogenic relatives); the many and varied routes of transmission from its major natural hosts, ruminant farm animals; and other aspects of its epidemiology, its virulence factors, the diagnosis and management of infection and their complications, the repercussions of infection including costs, and prevention.