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Evaluation of new in vitro efficacy test for antimicrobial surface activity reflecting UK hospital conditions

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Evaluation of new in vitro efficacy test for antimicrobial surface activity reflecting UK hospital conditions

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Abstract

Antimicrobial surfaces aim to reduce microbial bioburden and improve hygiene. The current antimicrobial surface efficacy test (ISO22196) is an initial screening test but its conditions, high temperature (37°C) and relative humidity (RH) (100%) bear little relationship to in-use conditions. To develop an antimicrobial surface efficacy test providing a realistic second-tier test, simulating in-use conditions. Surface relative humidity, temperature and soiling were measured over one year at a UK hospital, enabling realistic parameters to be set for our surface efficacy test. A nebulizer, connected to a cascade impactor, aerosolized and uniformly deposited a Staphylococcus aureus suspension over test copper alloys and control stainless steel surfaces. Bacteria were enumerated following nebulization, and after a range of contact times, under [20°C, 50% RH] and [20°C, 40% RH] parameters reflecting in-use conditions; [37°C, 100% RH] was employed to reflect conditions used in ISO22196. All copper alloys produced a >4 log10 reduction after 24h under all conditions tested. Copper alloys were more effective at [37°C, 100% RH] showing a >4 log10 reduction after 30min than at in-use conditions [20°C, 50% RH and 20°C, 40% RH], for which 60min was required to achieve the same level of kill, for most but not all alloys. The use of the nebulizer to deposit bacterial inocula on surfaces showed little variability in results. Our method was more discriminatory than the ISO22196 enabling distinction between the bactericidal surface activity, which allows for a more rigorous selection of antimicrobial surfaces for potential use in healthcare settings.

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... Microbes are tiny living things that are omnipresent in our environmental setting, and their harmful effect may cause many infectious and non-infectious diseases. It is well known that bacteria, yeast, and filamentous molds are some common types of pathogenic organisms that could survive for prolonged periods on varieties of frequently contacting surfaces such as currency notes, mobile phones, doorknobs, sinks, toilet seats, bed rails, light switches, etc [1][2][3]. These contaminated surfaces serve as the potential reservoirs of microbes that facilitate microbial transmission with the same frequency as contact with the colonized patients. ...
... Based on the aforementioned analysis and experimental results, a Zscheme heterojunction with spatial charge carriers transport path is developed between the SnS and bilayered g-C 3 N 4 /PDA contact interface [31]. It is illustrated in Fig. 6a that under visible-light irradiation, the photoexcited electrons in the CB of SnS start moving to the VB of g-C 3 N 4 across the PDA layer, and recombine there with the h + , while the rest of the electrons in the CB of g-C 3 Accordingly, the PDA-modified SnS/g-C 3 N 4 hybrid photocatalyst reflects improved visible-light absorption response because of the strong interaction of chemically bonded interfaces between the SnS core and dual g-C 3 N 4 /PDA shell, thus improving the efficacy of photoexcited charge carriers separation, which may results in strong antimicrobial effect under visible-light irradiation. ...
... The photogenerated ein the CB of SnS easily transferred to the VB of g-C 3 N 4 across the PDA surface interface of the SnS/g-C 3 N 4 photocatalyst (reaction 7). The photoinduced ein the CB of g-C 3 It is worth mentioning that the PDA@SnS/g-C 3 N 4 hybrid photocatalyst provides a synergistic therapy platform with enhanced photoinactivation of varieties of infectious microbial pathogens. ...
Article
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Herein, we aimed to fabricate poly(dopamine) coated tin sulfide/graphitic-carbon nitride ([email protected]/g-C3N4) photocatalyst as a targeted bioactive nano-agent for the growth control of antimicrobial resistants’ using a combined solvothermal and chemically oxidative polymerization of dopamine synthesis technique. The as-synthesized materials were systematically characterized for crystallographic, morphological, and spectroscopic analysis, revealed that the g-C3N4 component is composed of discrete nanoparticles that couple with SnS nanoparticles anchoring g-C3N4 nanosheets and poly(dopamine) molecules as capping agents, resulting in tight bilayer contact interfaces. Therefore, effective charge carrier separation was observed in the final product upon visible-light illumination. When used as an antimicrobial agent, the resultant [email protected]/g-C3N4 composite strongly inactivated the growth of the Gram-positive–Enterococcus faecalis, Gram-negative–Pseudomonas aeruginosa, and two mold strains–Aspergillus fumigatus, Aspergillus flavus upon 0.60 J dose of visible-light treatment at a minimum concentration of 45 μg·ml⁻¹, respectively. Moreover, radical scavenger experiments confirm the •O2–, and h⁺ initial species in the system. Importantly, no antimicrobial effect is recorded for the non-irradiated samples, indicating that the developed materials are not innately virulent in the lack of visible light and can be safely used to control the growth and survivorship of both detrimental molds and bacteria in reducing the risk of healthcare-associated infections.
... For the application in AMP, the film (25.4 × 50.8 mm) is first inoculated with 50 μL of bacterial suspension containing 7 log CFU/mL (either E. coli or S. aureus to achieve a final density of 5.7 log CFU/mL on each film) and then it is fully covered with a plastic film and placed in a Petri dish. After 0 and 24 h of incubation at 35 • C and >90% relative humidity (Campos et al., 2016;Ojeil, Jermann, Holah, Denyer, & Maillard, 2013), the film is transferred to a stomacher bag containing an appropriate dilution solution, agitated, serially diluted and counted according to the viable cell count as previously described. To ensure the high humidity (>90%), it is suggested to place the Petri dish in a jar with a saturated solution of zinc sulfate (Ojeil et al., 2013). ...
... After 0 and 24 h of incubation at 35 • C and >90% relative humidity (Campos et al., 2016;Ojeil, Jermann, Holah, Denyer, & Maillard, 2013), the film is transferred to a stomacher bag containing an appropriate dilution solution, agitated, serially diluted and counted according to the viable cell count as previously described. To ensure the high humidity (>90%), it is suggested to place the Petri dish in a jar with a saturated solution of zinc sulfate (Ojeil et al., 2013). Bumbudsanpharoke et al. (2019) used a similar method to investigate the antimicrobial activity of LDPE-ZnO composite film (50 × 50 mm) on different foodborne pathogens. ...
... During the storage period, the sampling must be carried out at regular intervals, usually 5-7 times (Komitopoulou, 2011). At each sampling point, the sample (10 or 50 g) is aseptically removed from the container and is homogenized in 90 or 450 mL of peptone saline water (0.85% NaCl and 0.1% peptone), peptone water buffer (0.1% w/v), or maximum recovery diluent (MRD, 1 g/L peptone, 8.5 g/L sodium chloride) (Ojeil et al., 2013;R Razavi, Tajik, et al., 2020). Then, the sample is serially diluted, and the bacterial count is performed by plate count or most probable number (MPN; to increase the detection limit) methods using the adequate selective medium according to available standard protocols. ...
Article
Background: Appropriate food packaging maintains food safety and quality. The development of active packaging is a novel approach for food preservation, in which the interaction between food, packaging material, and the environment enhances food safety and quality. Antimicrobial packaging (AMP) is a type of active packaging that can be developed by incorporating different kinds and concentrations of antimicrobial substances to packaging polymers in order to increase product shelf life. Scope and approach: In the existing literature, different antimicrobial tests have been used to establish the efficiency of antimicrobials in AMP. The variety of testing procedures being used in these studies makes it difficult to interpret the data and reach a general conclusion, indicating the need to establish valid methodologies. This review provides information about the main aspects and general requirements of in vitro methodologies, both in culture media (e.g., agar- and broth-based methods) and in food matrix, for determination of antibacterial performance of antimicrobial films and solutions. Key findings and conclusions: Several factors seem to influence the antimicrobial performance of AMP, including the AMP preparation method, the testing method, the selected bacterial strain, the inoculation level, among others. In addition, each packaging material requires not only different testing methods but also the modification of the test in order to meet the requirement of the specific active packaging and ensure consistent and reliable results.
... The conditions imposed in the assay of antimicrobial performance set out in the JIS Z 2801 method differ from those reported under real conditions in hospitals [26]. Although such in vitro tests may not accurately recreate the desired conditions, they can be easily implemented and are useful in initial screening of new materials. ...
... These could be simulated in a laboratory setting by generating bacterial aerosols. Despite the importance of this issue, only a few studies address it [26,30]. Ojeil et al. [26] deposited an S. aureus suspension on copper surfaces and measured antibacterial activity at three different conditions of temperature and relative humidity (RH): those stated in ISO 22196 (37 • C, 100% RH) and two authentic conditions at 20 • C with 40% or 50% RH and 100%. ...
... Despite the importance of this issue, only a few studies address it [26,30]. Ojeil et al. [26] deposited an S. aureus suspension on copper surfaces and measured antibacterial activity at three different conditions of temperature and relative humidity (RH): those stated in ISO 22196 (37 • C, 100% RH) and two authentic conditions at 20 • C with 40% or 50% RH and 100%. The authentic conditions generated an antibacterial activity around half of that measured under the standard conditions. ...
Article
Full-text available
Our aim is to present a comprehensive review of the development of modern antibacterial metallic materials as touch surfaces in healthcare settings. Initially we compare Japanese, European and US standards for the assessment of antimicrobial activity. The variations in methodologies defined in these standards are highlighted. Our review will also cover the most relevant factors that define the antimicrobial performance of metals, namely, the effect of humidity, material geometry, chemistry, physical properties and oxidation of the material. The state of the art in contact-killing materials will be described. Finally, the effect of cleaning products, including disinfectants, on the antimicrobial performance, either by direct contact or by altering the touch surface chemistry on which the microbes attach, will be discussed. We offer our outlook, identifying research areas that require further development and an overview of potential future directions of this exciting field.
... Organic soiling of antimicrobial surfaces is a known cause of loss of activity and thus was investigated for surfaces containing PANI and P3ABA [25,71,84]. Surface activity of both PANI in film and P3ABA in film was decreased in the presence of organic matter (Figure 8). ...
... Additionally, contaminating organic matter may inactivate antimicrobial agents [86]. Typical organic contaminants on hospital surfaces include blood and faecal matter [25,71]. It is important that antimicrobial surfaces are tested in conditions, including contamination with organic matter, relevant to the application to verify that the surfaces will be sufficiently active in these settings [25]. ...
... Typical organic contaminants on hospital surfaces include blood and faecal matter [25,71]. It is important that antimicrobial surfaces are tested in conditions, including contamination with organic matter, relevant to the application to verify that the surfaces will be sufficiently active in these settings [25]. ...
Article
Full-text available
Antimicrobial surfaces can be applied to break transmission pathways in hospitals. Polyaniline (PANI) and poly(3-aminobenzoic acid) (P3ABA) are novel antimicrobial agents with potential as non-leaching additives to provide contamination resistant surfaces. The activity of PANI and P3ABA were investigated in suspension and as part of absorbent and non-absorbent surfaces. The effect of inoculum size and the presence of organic matter on surface activity was determined. PANI and P3ABA both demonstrated bactericidal activity againstEscherichia coliandStaphylococcus aureusin suspension and as part of an absorbent surface. Only P3ABA showed antimicrobial activity in non-absorbent films. The results that are presented in this work support the use of P3ABA to create contamination resistant surfaces.
... In response, extensive guidelines on control and prevention of contamination are in place, created by equipment manufacturers, public health departments, and healthcare organizations [1][2][3]. This environment has been acknowledged an important "reservoir" for microorganisms responsible for hospital-acquired infections [4]. It has been documented that hospital patients often shed organisms into their environments which can be picked up by healthcare workers [1,[5][6][7][8][9]. ...
... At the present time, stainless steel is common in hospital settings due to appearance, durability, and ease of cleaning. However, this material does not have inherent antimicrobial properties and studies have demonstrated that Clostridium difficile spores and methicillin-resistant Staphylococcus aureus (MRSA) can survive on stainless steel for up to five and seven months or more, respectively [4]. However, metallic copper surfaces have antimicrobial properties, demonstrating significant activity within 2 hours of inoculation [10]. ...
... A major obstacle in marketing novel antimicrobial surfaces is a lack of performance evidence based on efficacy test protocols. The testing protocol commonly used in industry is International Standard (ISO) 22196 titled "Plastics-Measurement of antibacterial activity on plastics surfaces [4,13]." In this protocol, surfaces are tested using a liquid bacterial culture, covered in a plastic film, and grown for 24 hours at high temperature and 100% relative humidity. ...
Article
Full-text available
Background: Contaminated hospital surfaces are an important source of nosocomial infections. A major obstacle in marketing antimicrobial surfaces is a lack of efficacy data based on standardized testing protocols. Aim: We compared the efficacy of multiple testing protocols against several "antimicrobial" film surfaces. Methods: Four clinical isolates were used: one Escherichia coli, one Klebsiella pneumoniae, and two Staphylococcus aureus strains. Two industry methods (modified ISO 22196 and ASTM E2149), a "dried droplet", and a "transfer" method were tested against two commercially available antimicrobial films, one film in development, an untreated control, and a positive (silver) control film. At 2 (only ISO) and 24 hours following inoculation, bacteria were collected from film surfaces and enumerated. Results: Compared to untreated films in all protocols, there were no significant differences in recovery on either commercial brand at 2 or 24 hours after inoculation. The silver surface demonstrated significant microbicidal activity (mean loss 4.9 Log10 CFU/ml) in all methods and time points with the exception of 2 hours in the ISO protocol and the transfer method. Using our novel droplet method, no differences between placebo and active surfaces were detected. The surface in development demonstrated variable activity depending on method, organism, and time point. The ISO demonstrated minimal activity at 2 hours but significant activity at 24 hours (mean 4.5 Log10 CFU/ml difference versus placebo). The ASTEM protocol exhibited significant differences in recovery of staphylococci (mean 5 Log10 CFU/ml) but not Gram-negative isolates (10 fold decrease). Minimal activity was observed with this film in the transfer method. Conclusions: Varying results between protocols suggested that efficacy of antimicrobial surfaces cannot be easily and reproducibly compared. Clinical use should be considered and further development of representative methods is needed.
... The ISO 22196 standard (Japanese test method JIS Z 2801) is used for the measurement of antibacterial activity on plastic surfaces 11 . However, some studies have described this test as inappropriate, since the temperature of incubation (35 ± 1 °C) and the relative humidity (higher than 90%) do not reflect real conditions 12 . Thus, alternative and more realistic methods for the in vitro study of antibacterial activity of plastic surfaces have been described 7,13 . ...
... Frequently-touched environmental surfaces play an important role as reservoirs and sources of microorganism transmission 10 . Microbial pathogens are able to survive on the surfaces for long time, and could be transferred and cause HAI in patients admitted to hospitals 12 . There are different current strategies to prevent the contamination www.nature.com/scientificreports/ of surfaces and therefore, reduce the possibility of patients' infection. ...
... Incubation time, initial bacterial concentration, bacterial phase of growth and nutrient concentration were critical factors that influenced the results of antibacterial testing. It has been demonstrated that the incubation conditions used in the ISO 22196 can influence the antibacterial activity of some materials 12,19 . Differences in the activity of silver-ion containing materials were observed when they were tested using the ISO 22196 conditions (high activity at > 90% relative humidity) instead of more realistic conditions of 22% relative humidity (nearly no activity) 19 . ...
Article
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One strategy to decrease the incidence of hospital-acquired infections is to avoid the survival of pathogens in the environment by the development of surfaces with antimicrobial activity. To study the antibacterial behaviour of active surfaces, different approaches have been developed of which ISO 22916 is the standard. To assess the performance of different testing methodologies to analyse the antibacterial activity of hydrophobic surface patterned plastics as part of a Horizon 2020 European research project. Four different testing methods were used to study the antibacterial activity of a patterned film, including the ISO 22916 standard, the immersion method, the touch-transfer inoculation method, and the swab inoculation method, this latter developed specifically for this project. The non-realistic test conditions of the ISO 22916 standard showed this method to be non-appropriate in the study of hydrophobic patterned surfaces. The immersion method also showed no differences between patterned films and smooth controls due to the lack of attachment of testing bacteria on both surfaces. The antibacterial activity of films could be demonstrated by the touch-transfer and the swab inoculation methods, that more precisely mimicked the way of high-touch surfaces contamination, and showed to be the best methodologies to test the antibacterial activity of patterned hydrophobic surfaces. A new ISO standard would be desirable as the reference method to study the antibacterial behaviour of patterned surfaces.
... The antibacterial efficacy is usually assessed after a time of exposure to the copper-containing surface using reduction in bacterial counts either compared to the initial inoculum and/or to the counts obtained on a control surface deprived of antibacterial properties such as glass, plastic or stainless steel ( Figure 2). These tests were first held on food pathogens and collection strains susceptible to antibiotics [51][52][53], but publications soon moved on to report significant reductions in bacterial counts on copper and copper alloy surfaces for a range of multidrug-resistant (MDR) bacteria and/or bacteria originating from clinical settings [32,[54][55][56][57][58][59][60][61][62][63][64][65][66][67][68][69]. Indeed, the importance of testing clinical strains to evaluate whether any co-selected, cross-selected and/or co-regulated resistance between copper and antibiotics and/or detergent-disinfectants could occur soon appeared as mandatory [62]. ...
... MRSA were shown to be as readily killed under high temperature and RH (35 °C and 90% RH) as under low temperature and RH (20 °C, 24% RH) [64]. However, pointing out that the 37 °C and 100% RH conditions recommended in the ISO 22196 [85] antimicrobial surface efficacy test were far from reflecting actual healthcare environmental conditions, Ojeil et al. proposed to test the antimicrobial activity of copper surfaces at either 20 °C, 50% RH or 20 °C, 40% RH [67]. They showed that the higher temperature and RH conditions allowed for a greater antimicrobial efficacy on a S. aureus strain of all copper alloys tested than those closer to actual environmental conditions. ...
... Using repeated soiling with S. aureus suspended in 1% Bovine Serum Albumin (BSA), a study showed that despite cleaning procedures, the efficiency of a copper surface against S. aureus was reduced [88]. However, Ojeil et al. later showed that the addition of BSA at 3 g/L did not significantly modify the antibacterial activity of a series of copper alloys against S. aureus [67]. Some copper alloys even displayed a better efficacy when the BSA soil load was present [67]. ...
Article
Full-text available
Copper has been used for its antimicrobial properties since Antiquity. Nowadays, touch surfaces made of copper-based alloys such as brasses are used in healthcare settings in an attempt to reduce the bioburden and limit environmental transmission of nosocomial pathogens. After a brief history of brass uses, the various mechanisms that are thought to be at the basis of brass antimicrobial action will be described. Evidence shows that direct contact with the surface as well as cupric and cuprous ions arising from brass surfaces are instrumental in the antimicrobial effectiveness. These copper ions can lead to oxidative stress, membrane alterations, protein malfunctions, and/or DNA damages. Laboratory studies back up a broad spectrum of activity of brass surfaces on bacteria with the possible exception of bacteria in their sporulated form. Various parameters influencing the antimicrobial activity such as relative humidity, temperature, wet/dry inoculation or wear have been identified, making it mandatory to standardize antibacterial testing. Field trials using brass and copper surfaces consistently report reductions in the bacterial bioburden but, evidence is still sparse as to a significant impact on hospital acquired infections. Further work is also needed to assess the long-term effects of chemical/physical wear on their antimicrobial effectiveness.
... Frequently-touched environmental surfaces play an important role as reservoirs and sources of microorganism transmission 10 . Microbial pathogens are able to survive on the surfaces for long time, and could be transferred and cause HAI in patients admitted to hospitals 12 . There are different current strategies to prevent the contamination of surfaces and therefore, reduce the possibility of patients' infection. ...
... Four critical factors that in uence the outcome of antibacterial testing in a series of experiments were described: (1) incubation time, (2) bacteria starting concentration, (3) physiological state of bacteria (stationary or exponential phase of growth), and (4) nutrient concentration. It has been demonstrated that the incubation conditions used in the ISO 22196 can in uence the antibacterial activity of some materials 12,19 . Differences in the activity of silver-ion containing materials were observed when they were tested using the ISO 22196 conditions (high activity at > 90% relative humidity) instead of more realistic conditions of 22% relative humidity (nearly no activity) 19 . ...
Preprint
Full-text available
Background: One strategy to decrease the incidence of hospital-acquired infections is to avoid the survival of pathogens in the environment by the development of surfaces with antimicrobial activity. To study the antimicrobial behaviour of active surfaces, different approaches have been developed of which ISO 22916 is the standard. Aim: To assess the performance of different testing methodologies to analyse the antimicrobial activity of hydrophobic surface patterned plastics as part of a Horizon 2020 European research project (FLEXPOL: Antimicrobial FLEXible POLymers for its use in hospital environments No. 721062). Methods: Four different testing methods were used to study the antimicrobial activity of a patterned film, including the ISO 22916 standard, the immersion method, the touch-transfer inoculation method, and the swab inoculation method, this latter developed specifically for this project. Findings: The non-realistic test conditions of the ISO 22916 standard showed this method to be non-appropriate in the study of hydrophobic antimicrobial patterned surfaces. The immersion method also showed no differences between patterned films and smooth controls due to the lack of attachment of testing bacteria on both surfaces. The antimicrobial activity of films could be demonstrated by the touch-transfer and the swab inoculation methods that more precisely mimicked the way of high-touch surfaces contamination. Conclusion: The touch-transfer and the swab inoculation methods proved to be the best methodologies to test the antimicrobial activity of patterned hydrophobic surfaces. In our opinion, a new ISO standard should be developed on the basis of these tests to study the antimicrobial behaviour of patterned surfaces.
... Mo provides greater corrosion resistance and improved hardness, which makes it great for sharp cutting edges, such as surgical scalpels. As a result of superior mechanical properties, 316 has been the preferred stainless steel alloy, and is recommended for medical devices [28] such as coronary stents, hip-implant stems and spinal-disc replacements. SS is also used for a variety of surgical tools such as scalpels and forceps, as well as for operating tables. ...
... Since SS is inert, it does not have sufficient antimicrobial properties for more demanding applications and surface modification must be performed. There are few microorganisms that can persist on surfaces for several months like Clostridium difficile spores and methicillin-resistant Staphylococcus aureus (MRSA) [28]. In order to reduce the contamination of surfaces, more extensive guidelines and standardized methods must be developed to achieve reliable, reproducible results for antibacterial activity. ...
Article
Full-text available
In this review, strategies for improving the antimicrobial properties of stainless steel (SS) are presented. The main focus given is to present current strategies for surface modification of SS, which alter surface characteristics in terms of surface chemistry, topography and wettability/surface charge, without influencing the bulk attributes of the material. As SS exhibits excellent mechanical properties and satisfactory biocompatibility, it is one of the most frequently used materials in medical applications. It is widely used as a material for fabricating orthopedic prosthesis, cardiovascular stents/valves and recently also for three dimensional (3D) printing of custom made implants. Despite its good mechanical properties, SS lacks desired biofunctionality, which makes it prone to bacterial adhesion and biofilm formation. Due to increased resistance of bacteria to antibiotics, it is imperative to achieve antibacterial properties of implants. Thus, many different approaches were proposed and are discussed herein. Emphasis is given on novel approaches based on treatment with highly reactive plasma, which may alter SS topography, chemistry and wettability under appropriate treatment conditions. This review aims to present and critically discuss different approaches and propose novel possibilities for surface modification of SS by using highly reactive gaseous plasma in order to obtain a desired biological response.
... 7 Parts of the document (e.g., criteria for disinfectant and sanitizer claims, selection of microorganisms, and exposure times used) were adapted from protocols used to assess chemical disinfectants; however, this may not be appropriate for evaluating solid surfaces where antimicrobial effect is continuous and the mechanisms of antimicrobial action differ compared to chemical disinfectants. 11,12 Further, the cleaner/ disinfectants in the EPA protocol do not reflect the types or concentration of products currently used in healthcare nor their mechanical application to surfaces using microfiber cloths, rags, or disinfectant wipes. 13 The modifications were not compared to the current EPA protocol for differences in outcome because the alterations made were essential in order to reflect the type of cleaning and disinfection in healthcare (https://www.picnet.ca/wp-ontent/ ...
... Adapting the EPA protocol to better reflect hospital cleaning practices was important when assessing the antimicrobial activity of these surfaces. 11 It was equally important to objectively measure the durability of the different formulations-the main concerns being resistance to wear, corrosion, and compatibility with hospitalgrade disinfectants. 14 Answering the fundamental questions of sustainability of antimicrobial action and durability of Cu alloy FIG. 2. Average thickness loss of spray-on Cu carrier treated with cleaner/disinfectants after 1 year simulated use with Wiperator™. ...
Article
Antimicrobial properties of solid copper (Cu) surfaces against various microorganisms have been demonstrated, but little is known about the durability and relative antimicrobial efficacy of different Cu formulations currently used in healthcare. The aim of this study was to assess whether three different formulations of copper-bearing alloys (integral, spray-on and Cu-impregnated surfaces) and a stainless steel control differed in their antimicrobial efficacy, durability, and compatibility with hospital-grade cleaner/disinfectants. The U.S. Environmental Protection Agency draft protocol for the evaluation of bactericidal activity of Cu containing alloys was modified to more accurately reflect cleaning methods in healthcare. The three different Cu alloys were evaluated using 25 × 25 × 3 mm disks subjected to one year of simulated cleaning and disinfection using the Wiperator™ with microfiber cloths presoaked in three common hospital disinfectants: accelerated hydrogen peroxide, quaternary ammonium, or sodium hypochlorite solutions. Bactericidal activity was evaluated using Staphylococcus aureus and Pseudomonas aeruginosa. While all Cu formulations exhibited some antimicrobial activity, integral and spray-on Cu alloys showed the greatest efficacy. Assessments of durability included documentation of changes in mass, morphological changes by scanning electron microscopy, chemical composition alteration by energy-dispersive x-ray spectroscopy, and surface roughness alteration using profilometry over one year of simulated use. The integral Cu alloy had the least mass loss (0.20% and 0.19%) and abrasion-corrosion rate (6.28 and 6.09 μm/yr) compared to stainless steel. The integral product also showed the highest durability. Exposure to disinfectants affected both the antimicrobial efficacy and durability of the various copper products.
... Other studies at clinical settings show only modest microbial reductions [6]. Controversial findings of the antimicrobial efficiency of Cu are suggested to mainly relate to inconsistent test conditions of various standards, such as relative humidity and temperature [29,30], wet or dry applications [19,31,32], different bacterial strains [19,32,33], and chemical environments [34,35]. ...
Article
Full-text available
Metal-based high-touch surfaces used for indoor applications such as doorknobs, light switches, handles and desks need to remain their antimicrobial properties even when tarnished or degraded. A novel laboratory methodology of relevance for indoor atmospheric conditions and fingerprint contact has therefore been elaborated for combined studies of both tarnishing/corrosion and antimicrobial properties of such high-touch surfaces. Cu metal was used as a benchmark material. The protocol includes pre-tarnishing/corrosion of the high touch surface for different time periods in a climatic chamber at repeated dry/wet conditions and artificial sweat deposition followed by the introduction of bacteria onto the surfaces via artificial sweat droplets. This methodology provides a more realistic and reproducible approach compared with other reported procedures to determine the antimicrobial efficiency of high-touch surfaces. It provides further a possibility to link the antimicrobial characteristics to physical and chemical properties such as surface composition, chemical reactivity, tarnishing/corrosion, surface roughness and surface wettability. The results elucidate that bacteria interactions as well as differences in extent of tarnishing can alter the physical properties (e.g. surface wettability, surface roughness) as well as the extent of metal release. The results clearly elucidate the importance to consider changes in chemical and physical properties of indoor hygiene surfaces when assessing their antimicrobial properties.
... It is true to say, however, that continued research on these surfaces is needed and will no doubt attract much interest from business and industry in the future. There has already been a call for scientific standards for antimicrobial surfaces in view of the rapidly expanding technologies and potential importance of these products (235). ...
Article
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There is increasing interest in the role of cleaning for managing hospital-acquired infections (HAI). Pathogens such as vancomycin-resistant enterococci (VRE), methicillin-resistant Staphylococcus aureus (MRSA), multiresistant Gram-negative bacilli, norovirus, and Clostridium difficile persist in the health care environment for days. Both detergent- and disinfectant-based cleaning can help control these pathogens, although difficulties with measuring cleanliness have compromised the quality of published evidence. Traditional cleaning methods are notoriously inefficient for decontamination, and new approaches have been proposed, including disinfectants, steam, automated dispersal systems, and antimicrobial surfaces. These methods are difficult to evaluate for cost-effectiveness because environmental data are not usually modeled against patient outcome. Recent studies have reported the value of physically removing soil using detergent, compared with more expensive (and toxic) disinfectants. Simple cleaning methods should be evaluated against nonmanual disinfection using standardized sampling and surveillance. Given worldwide concern over escalating antimicrobial resistance, it is clear that more studies on health care decontamination are required. Cleaning schedules should be adapted to reflect clinical risk, location, type of site, and hand touch frequency and should be evaluated for cost versus benefit for both routine and outbreak situations. Forthcoming evidence on the role of antimicrobial surfaces could supplement infection prevention strategies for health care environments, including those targeting multidrug-resistant pathogens.
... To mimic near dry conditions of frequently touched surfaces in a hospital setting, we have developed a facile "dry seeding" approach to simulate low humidity conditions representative of the surface of the skin and to study the effectiveness of anodized aluminum coupons in inhibiting cross-contaminations. Also, the MRD load (9.5 g/L peptone) has been utilized to simulate soiling conditions of vomit, blood, or faecal spills. 32 Briefly, a 5-μL aliquot suspension of E. coli inoculum (1.5 × 10 8 ) was seeded on a sterile 1″ × 1″ area of test and control coupons. To ensure bacteria inoculum covered entire coupons and edges, the former was evenly spread using sterile bent disposable pipet tips (Mettler-Toledo). ...
... 2.1. Temperature and humidity Ojeil et al., 2013 initiated tests to recognize the inappropriateness of an efficacy test protocol of antimicrobial surfaces. For this study, copper surface antimicrobial activity was tested depending on temperature, ambient relative humidity and soiling, according to a modified JIS Z 2801 protocol. ...
Conference Paper
Copper has long been known to have antimicrobial activity and is used in drinking water treatment and transportation. It has been recognized by the American Environmental Protection Agency as the first metallic antimicrobial agent in 2008. With ongoing waterborne hospital-acquired infections and antibiotic resistance, research on copper as an antimicrobial agent is again very attractive. Many studies have shown that the use of copper surface and copper particles could significantly reduce the environmental bioburden. This review highlights in its first part all the conditions described in the literature to enhance copper antimicrobial activity. Secondly, the different antimicrobial applications of copper in water treatment, hospital care units and public applications are presented. Finally, the future research needs on copper as an antimicrobial agent are discussed.
... The results obtained in this study are consistent with the results obtained by other authors in terms of confirming the stronger antimicrobial activity of copper in comparison with its alloys [25][26][27][28][29][30]. However, in this study, differences were observed regarding the rate of reduction in the initial EC and SA bacterial suspensions in comparison with studies by other authors. ...
Article
Full-text available
Background: Hospital equipment made from copper alloys can play an important role in complementing traditional methods of disinfection.Aims of the study:The aim of this study was to assess the dynamics of the antimicrobial properties of selected copper alloys in different simulations of environmental conditions (with organic contamination vs. without organic contamination), and to test alternatives to the currently used testing methods.Materials and Methods:A modification of Japanese standard JIS Z 2801 as well asStaphylococcus aureus(SA) andEscherichia coli(EC) suspended in NaCl vs. tryptic soy broth (TSB) were used in tests performed on seven commonly used copper alloys, copper, and stainless steel.Results:A much faster reduction of the bacterial suspension was observed for the inoculum prepared in NaCl than in TSB. A faster reduction for EC than for SA was observed in the inoculum prepared in NaCl. The opposite results were found for the inoculum based on TSB. A significant correlation between the copper concentration in the copper alloys and the time and degree of bacterial suspension reduction was only observed in the case of EC.Conclusions:This study confirmed the antimicrobial properties of copper alloys, and additionally showed thatStaphylococcus aureuswas more resistant thanEscherichia coliin the variant of the experiment without organic contamination. However, even for SA, a total reduction of the bacterial inoculum's density took no longer than 2 h. Under conditions simulating organic contamination, all of the tested alloys were shown to have bactericidal or bacteriostatic properties, which was contrary to the results from stainless steel.
... Characteristic of selected for tests of susceptibility for copper alloys CNS strains handles in hospital wards, was 1-6 × 10 3 CFU[18] and therefore, the criteria proposed by Souli et al. can be deemed to be appropriate for testing the antimicrobial efficacy of products made of copper and its alloys. The results are presented in ...
Article
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Background Despite the employment of sanitary regimes, contact transmission of the aetiological agents of hospital infections is still exceedingly common. The issue of microbe transmission becomes particularly important when facing multidrug-resistant microorganisms such as methicillin-resistant staphylococci. In the case of deficiencies in cleaning and disinfection procedures, hospital equipment made of copper alloys can play an important role, complementing traditional hospital hygiene procedures.The objective of this study was to characterize staphylococcal strains isolated from touch surfaces in Polish hospital wards in terms of their drug resistance, ability to form biofilm and susceptibility to antimicrobial activity of copper alloys. Methods The materials for the study were 95 staphylococcal strains isolated from touch surfaces in 13 different hospital wards from Małopolska province (the south of Poland). Phenotypic and genotypic antibiotic resistance were checked for erythromycin, clindamycin, gentamycin, ciprofloxacin, trimethoprim/sulfamethoxazole and mupirocin. Biofilm formation ability for the tested strains was checked with the use of culture on Congo red agar. Susceptibility to copper, tin bronze, brass and new silver was tested using a modification of the Japanese standard. ResultsOver 67% of the analysed staphylococcal strains were methicillin-resistant (MR). Four strains were resistant to all of the tested antibiotics, and 14 were resistant to all except mupirocin. Strains classified as MR had significantly increased resistance to the remaining antibiotic groups. About one-third of the analysed strains revealed biofilm-forming ability. Among the majority of species, biofilm-forming and non-biofilm-forming strains were distributed evenly; in the case of S. haemolyticus only, negative strains accounted for 92.8%. Susceptibility to copper alloys was different between strains and rather lower than in the case of the SA strain selected for comparison. Conclusions Coagulase-negative staphylococci, the most commonly isolated in Polish hospital wards, should not be neglected as an infection risk factor due their high antibiotic resistance. Our experiments confirmed that touch surfaces made of copper alloys may play an important role in eliminating bacteria from the hospital environment.
... Items within hospital room and crowded places which are frequently touched are a likely reservoir for microbes and allowing them to transfer from one person to another [2,3]. Usually, stainless steel is one of the most well-known touch surface materials since it appears to be clean and resistant to corrosion [4,5]. Nevertheless, in areas where microbial surface contamination is an issue, stainless steel surface may not be the best choice because it has no ability to reduce the microbial load on its surface [6]. ...
Conference Paper
The utilization of copper as antimicrobial touch surfaces offers a solution that can serve as an additional line of defense against hospital acquired infections. In order to make use of the antimicrobial ability of copper, touch surfaces should compose of copper either solid copper or copper coating. In general, cost considerations favor copper coating over solid copper. In this study, copper coating was deposited on 304 stainless steel substrate using chronoamperometry technique performed in a typical three-electrode cell. Electrodeposition process was obtained in pH 8 EDTA solution containing 0.01 M Cu²⁺ ions at -1.1 V vs Ag/AgCl for 15 min. A uniform, compact and dense nano-sized (38-66 nm) coating was deposited on 304 stainless steel surface, as observed by FESEM. EDX analysis showed a high percentage of copper (97.95 wt.%) with uniform distribution on the entire surface of 304 stainless steel. Surface topography and roughness of the sample were investigated by AFM. Numerous 3D copper clusters can be recognized on 304 stainless steel surface with the average roughness of 24.23 nm. The antibacterial result indicated that the copper coating has excellent antibacterial activity against E. coli (100 % reduction within 5 min of exposure) and S. aureus (100 % reduction within 10 min of exposure) compared to 304 stainless steel (no reduction even after 30 min of exposure).
... Because of a number of microorganisms' ability to persist and survive for longterm periods on surfaces, particularly in healthcare settings, the usage of antimicrobially impregnated surfaces is increasingly discussed [82]. However, because of the required long contact times of microorganisms on antimicrobial surfaces [64,65,25,45], such technologies may be useful for surfaces with low frequency of hand contacts. ...
Chapter
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In healthcare settings microbial contaminated surfaces play an important role in indirect transmission of infection. Especially surfaces close to the patients’ environment may be touched at high frequencies, allowing transmission from animated sources to others via contaminated inanimate surfaces. Therefore, the knowledge on the survival of bacteria, fungi, viruses and protozoa on surfaces, and hence, in a broader sense, in the human environment, is important for implementing tactics for prevention of Healthcare-acquired Infections (HAI). This chapter will elaborate the role of surfaces in the transmission of pathogens. Particular emphasis is laid on the current knowledge of the survival time and conditions favouring survival of the pathogens. Finally, mechanisms of transmission from inanimate surfaces to patients are highlighted. Within the multi-barrier strategy of the prevention of HAI, environmental disinfection policies should be based on risk assessments for surfaces with different risks for cross contamination such as high- and low-touched surfaces with appropriate standards for adequate disinfection measures under consideration of the persistence and infectious dose of the pathogens. As a result, surface disinfection is indicated in the following situations: Frequently touched surfaces adjacent to patients Surfaces with assumed or visible contamination Terminal disinfection in rooms or areas where infected or colonized patients with easily transferable nosocomial pathogens are cared for, and in outbreak situations. Furthermore, the knowledge of the persistence of pathogens will also support ensuring the biosafety in microbiological and biomedical laboratories, food-handling settings, and for hygienic behaviour in the everyday life to prevent transmission of infectious diseases.
... Therefore, efforts should be undertaken to characterize typical wear, assess interactions with the most likely micro-organisms in that environment, and define the most appropriate and least damaging cleaning and sanitizer regimes. The best way to achieve such outcomes is to ensure that multidisciplinary expertise is integrated into developmental processes, and that testing methods are appropriately robust [8]. ...
Article
The spread of infections in health care environments is a persistent and growing problem in most countries, aggravated by the development of microbial resistance to antibiotics and disinfectants. In addition to indwelling medical devices (implants, catheters, etc.), such infections may also result from adhesion of microbes either to external solid-water interfaces such as shower caps, taps, drains, etc, or to external solid-gas interfaces such as door handles, clothes, curtains, computer keyboards, etc. The latter are the main focus of the present work, where an overview of antimicrobial coatings for such applications is presented. The paper addresses well-established and novel methodologies, including chemical and physical functional modification of surfaces to reduce microbial contamination, as well as the potential risks associated to the implementation of such anti-contamination measures. Different chemistry-based approaches are discussed, in particular anti-adhesive surfaces (e.g., superhydrophobic, zwitterions, etc.) contact-killing surfaces (e.g., polymer brushes, phages, etc.) and biocide-releasing surfaces (e.g., triggered release, quorum sensing-based systems, etc.). The paper also assesses the impact of topographical modifications at distinct dimensions (micrometre and nanometre orders of magnitude) and the importance of applying safe-by-design criteria (toxicity, contribution for unwanted acquisition of antimicrobial resistance, long-term stability, etc.) when developing and implementing antimicrobial surfaces.
... Environmental conditions can also have a significant influence on the antimicrobial effect of Cu surfaces. Ojeil et al. [36], showed that Cu alloys gave a >4-log reduction in S. aureus after 30 min at 37 • C and 100% RH. However, when conditions of 20 • C and 40% or 50% RH were imposed, the same effect took 60 min. ...
Article
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International interest in metal-based antimicrobial coatings to control the spread of bacteria, fungi, and viruses via high contact human touch surfaces are growing at an exponential rate. This interest recently reached an all-time high with the outbreak of the deadly COVID-19 disease, which has already claimed the lives of more than 5 million people worldwide. This global pandemic has highlighted the major role that antimicrobial coatings can play in controlling the spread of deadly viruses such as SARS-CoV-2 and scientists and engineers are now working harder than ever to develop the next generation of antimicrobial materials. This article begins with a review of three discrete microorganism-killing phenomena of contact-killing surfaces, nanoprotrusions, and superhydrophobic surfaces. The antimicrobial properties of metals such as copper (Cu), silver (Ag), and zinc (Zn) are reviewed along with the effects of combining them with titanium dioxide (TiO2) to create a binary or ternary contact-killing surface coatings. The self-cleaning and bacterial resistance of purely structural superhydrophobic surfaces and the potential of physical surface nanoprotrusions to damage microbial cells are then considered. The article then gives a detailed discussion on recent advances in attempting to combine these individual phenomena to create super-antimicrobial metal-based coatings with binary or ternary killing potential against a broad range of microorganisms, including SARS-CoV-2, for high-touch surface applications such as hand rails, door plates, and water fittings on public transport and in healthcare, care home and leisure settings as well as personal protective equipment commonly used in hospitals and in the current COVID-19 pandemic.
... The standard test methods generally approved and frequently used for antimicrobial efficacy assessment in Europe, US and Japan [12][13][14][15] usually require the placement of a small volume of microbial suspension onto the tested surface, incubation in wet or dry conditions during a pre-determined time, and subsequent assessment of microbial viability, 24-48 h after agar plating. Although testing in "dry" conditions may be closer to real environmental conditions 5,16 several studies have shown that this test format is more prone to errors due toot experimental variations e.g., in humidity and temperature 9 which suggests that testing in "wet" conditions may be more reliable and needs less optimization for screening purposes. ...
Article
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Release of metal ions from metal-based surfaces has been considered one of the main drivers of their antimicrobial activity. Here we describe a method that enables parallel assessment of metal ion release from solid metallic surfaces and antimicrobial efficacy of these surfaces in a short time period. The protocol involves placement of a small volume of bioluminescent bacteria onto the tested surface and direct measurement of bioluminescence at various time points. In this study, two recombinant Escherichia coli strains, one expressing bioluminescence constitutively and applicable for general antimicrobial testing, and the other induced by Cu ions, were selected. Decrease in bioluminescence of constitutive E. coli on the surfaces showed a good correlation with the decrease in bacterial viability. Response of Cu-inducible E. coli showed a correlation with Cu content in the tested surfaces but not with Cu dissolution suggesting the role of direct bacteria-surface contact in Cu ion-driven antibacterial effects. In summary, the presented protocol enables the analysis of microbial toxicity and bioavailability of surface-released metal ions directly on solid surfaces within 30–60 min. Although optimized for copper and copper alloy surfaces and E. coli, the method can be extended to other types of metallic surfaces and bacterial strains.
... The MRD contained 9.5 g/L peptone, which contributes to soiling on surfaces. 36 Tests were conducted on both the test and control samples (sterile 1 × 1 inch square: (a) Ag−PMHS−QUAT nanocomposite-coated AAO/Al coupon; (b) antimicrobial copper coupon (C11000 of 99.9% Cu); (c) UmanProTek (a patented technology developed by A3 Surfaces 37 ); (d) QUAT-coated AAO/Al; (d) Ag-coated AAO/Al; and (e) AAO/Al). As sterilization techniques such as flaming, autoclaving, or UV radiation could alter the antimicrobial properties of coupons, 38 sterilization was achieved by immersing in 70% ethanol for10 min in a biological hood. ...
Article
Multidrug-resistant bacteria are known to survive on high-touch surfaces for days, weeks, and months, contributing to the rise in nosocomial infections. Inducing antibacterial property in such surfaces can presumably reduce the overall microbial burden and subsequent nosocomial infections in hygiene critical environments. In the present study, a one-pot sol-gel process has been deployed to incorporate silver (Ag) and quaternary ammonium salt (QUAT) bactericides in a polymethylhydrosiloxane (PMHS) matrix. The Ag-PMHS-QUAT nanocomposite was coated on anodized aluminum (AAO/Al) by a simple ultrasound-assisted deposition process. The morphological features and chemical composition of the Ag-PMHS-QUAT nanocomposite have been characterized using SEM, XRD spectroscopy, and attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) to confirm the formation of Ag-QUAT nanocomposites within the polymeric network of PMHS. The Ag-PMHS-QUAT nanocomposite coating on anodized aluminum oxide (AAO/Al) coupon exhibited superior antibacterial property with a 6-log bacterial reduction compared to the 5-log reduction for the commercially available antimicrobial copper coupon.
... A lower cost alternative to silver is copper (Cu), which has been used as a disinfection agent in various fields [22][23][24][25]. Aside from its direct toxicity to microorganisms, copper is also capable of triggering the formation of intracellular ROS through a Fenton-like reaction [26,27], which negatively impacts microorganisms. ...
Article
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This work investigates the effect of high voltage (HV) electrode material of a point-plane plasma reactor on the inactivation rate of E. coli in both direct plasma and post-discharge inactivation processes. For the direct plasma processes, nickel chromium alloy, iron, tungsten and copper were used as HV electrode materials. In comparison with the other three materials, a significantly higher inactivation rate of E. coli was achieved with copper as the HV electrode. The inactivation effect was demonstrated to be mainly associated with the toxicity of copper ions, rather than from copper nanoparticles released from the electrode during the treatment. Similarly, for the post-discharge inactivation process, a higher E. coli inactivation rate was achieved in both post-plasma and plasma-treated water treatment using copper as the HV electrode, as compared to the tungsten control case. Increased inactivation rates are a result of a synergistic action between copper ions and the hydrogen peroxide generated by the plasma.
... Several studies have shown effectiveness and potential of self-disinfecting surfaces in in-vitro assays [22,23]. ...
... Altogether, our results demonstrate the need to dene the appropriate applications and the most suitable and least damaging sanitation protocols for antibacterial materials in order to assess the durability of their antibacterial properties. 116,117 Along the same line, most international standards are in the process of being updated since they do not currently assess the time and cleaning products' impacts on the antibacterial properties of materials, and they do not consider the conditions of use. ...
Article
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Infections caused by multidrug-resistant bacteria are a major public health problem. Their transmission is strongly linked to cross contamination via inert surfaces, which can serve as reservoirs for pathogenic microorganisms. To address this problem, antibacterial materials applied to high-touch surfaces have been developed. However, reaching a rapid and lasting effectiveness under real life conditions of use remains challenging. In the present paper, hard-anodized aluminum (AA) materials impregnated with antibacterial agents (quaternary ammonium compounds (QACs) and/or nitrate silver (AgNO3)) were prepared and characterized. The thickness of the anodized layer was about 50 μm with pore diameter of 70 nm. AA with QACs and/or AgNO3 had a water contact angle varying between 45 and 70°. The antibacterial activity of the materials was determined under different experimental settings to better mimic their use, and included liquid, humid, and dry conditions. AA-QAC surfaces demonstrated excellent efficiency, killing >99.9% of bacteria in 5 min on a wide range of Gram-positive (Staphylococcus aureus, Clostridioides difficile, vancomycin-resistant Enterococcus faecium) and Gram-negative (streptomycin-resistant Salmonella typhimurium and encapsulated Klebsiella pneumoniae) pathogens. AA-QACs showed a faster antibacterial activity (from 0.25 to 5 min) compared with antibacterial copper used as a reference (from 15 min to more than 1 h). We show that to maintain their high performance, AA-QACs should be used in low humidity environments and should be cleaned with solutions composed of QACs. Altogether, AA-QAC materials constitute promising candidates to prevent the transmission of pathogenic bacteria on high-touch surfaces.
... The parameters used in the test, like humidity, temperature, presentation of the inoculums, and duration of incubation, do not reflect real-life application conditions, which could have led to overestimation of the efficacy of an antibacterial coating. 13 In this sense, the close reinforced contact between bacteria and the film at high-load conditions is the opposite to low, incidental deposition of bacteria on different shaped surfaces that may occur outside the research setting. Therefore, it should be recommended to use the ISO 22196 only as a measure for the intrinsic, maximal efficacy. ...
Article
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Background: Bacterial resistance against the classic antibiotics is posing an increasing challenge for the prevention and treatment of infections in health care environments. The introduction of antimicrobial nanocoatings with active ingredients provides alternative measures for active killing of microorganisms, through a preventive hygiene approach. Purpose: The purpose of this study was to investigate the antimicrobial activity of a panel of antimicrobial coatings available on the European market. Methods: A comparative, biased selection of commercially available antimicrobial coatings was tested for antimicrobial efficiency. Suppliers were contacted to deliver their coatings on glass and/or stainless steel substrates. In total, 23 coatings from eleven suppliers were received, which were investigated for their effect on the growth of Escherichia coli, using the International Organization for Standardization (ISO) 22196 protocol. Results: The majority of nanomaterial-containing coatings (n=13) contained nanosilver (n=12), while only one had photocatalytic TiO2 as the active particle. The differences in antimicrobial activity among all of the coatings, expressed as log reduction values, varied between 1.3 and 6.6, while the variation within the nanomaterial-based group was between 2.0 and 6.2. Although nanosilver coatings were on average very effective in reducing the number of viable bacteria after challenge, the strongest log reduction (6.6) was seen with a coating that has immobilized, covalently bound quaternary ammonium salt in its matrix. Besides these two compounds, coatings containing TiO2, poly(dimethylsiloxane), triclosan, or zinc pyrithione evoked 100% killing of E. coli. Conclusion: Our findings indicate that nanosilver dominates the nanoparticle-based coatings and performs adequately. However, considering the unknowns in relation to ecotoxicological emission and effects, it needs further consideration before widespread application into different environments.
... It is thought that organic compounds such as proteins provide a protective matrix for the bacteria from the copper ions and, in turn, reduce their antibacterial effect [2,3,35,36]. In comparison to this, another study observed an increase in antimicrobial activity when the bacterial inoculum was exposed to albumin, but these results could not be explained yet [37]. ...
Article
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In this study, assessment of the antimicrobial activity of a novel, plasma-cured 2.5% (w/v) Cu(NO3)2-containing sol–gel surface was performed. In contrast to state-of-the-art sol–gel coatings, the plasma curing led to a gradient in cross-linking with the highest values at the top of the coating. As a result, the coating behaved simultaneously hard, scratch-resistant, and tough, the latter due to the more flexible bulk of the coating toward the substrate. Further, the diffusion and permeation through the coating also increased toward the substrate. In our study, tests according to ISO 22196 showed antibacterial activity of the 2.5% (w/v) Cu(NO3)2-containing sol–gel surface against all bacterial strains tested, and we expanded the testing further using a “dry” evaluation without an aqueous contact phase, which confirmed the antimicrobial efficacy of the 2.5% (w/v) Cu(NO3)2-containing sol–gel surface. However, further investigation under exposure to soiling with the addition of 0.3% albumin, used to simulate organic load, led to a significant impairment in the antibacterial effect under both tested conditions. Furthermore, re-testing of the surface after disinfection with 70% ethanol led to a total loss of antibacterial activity. Our results showed that besides the mere application of an antimicrobial agent to a surface coating, it is also necessary to consider the future use of these surfaces in the experimental phase combining industry and science. Therefore, a number of tests corresponding to the utilization of the surface should be obligative on the basis of this assessment.
... For example, when assessing the activity of a copper alloy surface (with varying copper quantities in the alloy), incubating at 37 • C and 100% relative humidity (RH) provides a 4-log reduction in around 30 min for all alloys higher than 70% copper content. However, when the environmental conditions are more analogous to that of an indoor room, at approximately 20 • C and 40-50% RH, the time taken to achieve the same 4-log reduction of viable bacterial load is doubled to 60 min [80]. In addition, silver ions released from zeolite have demonstrated significant antimicrobial effect at >90% RH, but the same composition showed no significant antimicrobial effects at 24% RH and a temperature of 20 • C. ...
Article
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Materials that confer antimicrobial activity, be that by innate property, leaching of biocides or design features (e.g., non-adhesive materials) continue to gain popularity to combat the increasing and varied threats from microorganisms, e.g., replacing inert surfaces in hospitals with copper. To understand how efficacious these materials are at controlling microorganisms, data is usually collected via a standardised test method. However, standardised test methods vary, and often the characteristics and methodological choices can make it difficult to infer that any perceived antimicrobial activity demonstrated in the laboratory can be confidently assumed to an end-use setting. This review provides a critical analysis of standardised methodology used in academia and industry, and demonstrates how many key methodological choices (e.g., temperature, humidity/moisture, airflow, surface topography) may impact efficacy assessment, highlighting the need to carefully consider intended antimicrobial end-use of any product.
... 2.1. Temperature and humidity Ojeil et al., 2013 initiated tests to recognize the inappropriateness of an efficacy test protocol of antimicrobial surfaces. For this study, copper surface antimicrobial activity was tested depending on temperature, ambient relative humidity and soiling, according to a modified JIS Z 2801 protocol. ...
Article
Copper has long been known to have antimicrobial activity and is used in drinking water treatment and transportation. It has been recognized by the American Environmental Protection Agency as the first metallic antimicrobial agent in 2008. With ongoing waterborne hospital-acquired infections and antibiotic resistance, research on copper as an antimicrobial agent is again very attractive. Many studies have shown that the use of copper surface and copper particles could significantly reduce the environmental bioburden. This review highlights in its first part all the conditions described in the literature to enhance copper antimicrobial activity. Secondly, the different antimicrobial applications of copper in water treatment, hospital care units and public applications are presented. Finally, the future research needs on copper as an antimicrobial agent are discussed.
Chapter
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Aim Aim of this study was to evaluate the reduction on Intensive Care Unit (ICU) microbial flora after the antimicrobial copper alloy (Cu+) implementation as well as the effect on financial – epidemiological operation parameters. Methods Medical, epidemiological and financial data into two time periods, before and after the implementation of copper (Cu 63 % – Zn 37 %, Low Lead) were recorded and analyzed in a General ICU. The evaluated parameters were: the importance of patients’ admission (Acute Physiology and Chronic Health Evaluation – APACHE II and Simplified Acute Physiology Score – SAPS), microbial flora’s record in the ICU before and after the implementation of Cu+ as well as the impact on epidemiological and ICU’s operation financial parameters. Results During December 2010 and March 2011 and respectively during December 2011 and March 2012 comparative results showed statistically significant reduction on the microbial flora (CFU/ml) by 95 % and the use of antimicrobial medicine (per day per patient) by 30 % (p = 0.014) as well as patients hospitalization time and cost. Conclusions The innovative implementation of antimicrobial copper in ICUs contributed to their microbial flora significant reduction and antimicrobial drugs use reduction with the apparent positive effect (decrease) in both patients’ hospitalization time and cost. Under the present circumstances of economic crisis, survey results are of highest importance and value.
Chapter
Contaminated surfaces make an important contribution to the transmission of several important pathogens, including methicillin-resistant Staphylococcus aureus (MRSA), Clostridium difficile and a number of resistant Gram-negative rods, including Acinetobacter baumannii. Several different approaches are available for improving hospital hygiene, including improving the effectiveness of existing methods and a range of new approaches, including novel disinfectants. A complimentary approach is the introduction of antimicrobial surfaces (AMS), which exert a continuous reduction on the level of microbial contamination on hospitals surfaces. There are several approaches to making a hospital surface 'antimicrobial': permanently 'manufacture in' an agent with antimicrobial activity; periodically apply an agent with antimicrobial activity; or physically alter the properties of a surface to make it less able to support microbial contamination and/or easier to clean. Promising options for AMS in healthcare settings include metals (principally copper or silver), chemicals (organosilanes, quaternary ammonium compounds, light-activated antimicrobials, and polycationic polymers) and physical alteration of the surface to reduce microbial attachment or improve cleanability. Before widespread adoption of AMS, promising candidates require rigorous in vitro and in situ assessment, including an evaluation of their clinical impact and cost effectiveness. Copper alloy surfaces are the most closely evaluated option for AMS, and have demonstrated in vitro activity against a range of pathogens (although their sporicidal capacity remains equivocal), evidence of efficacy in in situ studies and their introduction has been associated with a reduction in healthcare-associated infections (HAI). However, their long-term durability, acceptability and cost-effectiveness have not been evaluated formally. Finding and evaluating the optimal AMS will require a multidisciplinary approach, involving industrial partners, materials scientists, healthcare scientists and epidemiologists to refine and test the available options. © 2014 Springer International Publishing Switzerland. All rights are reserved.
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Microbes tend to attach to available surfaces and form biofilms readily, which is problematic in healthcare settings. Biofilms are traditionally associated with wet or damp surfaces such as indwelling medical devices and tubing on medical equipment. However, microbes can survive for extended periods in a desiccated state on dry hospital surfaces, and biofilms have recently been discovered on dry hospital surfaces. Microbes attached to surfaces and in biofilms are less susceptible to biocides, antibiotics and physical stress. Thus, surface attachment and/or biofilm formation may explain how vegetative bacteria can survive on surfaces for weeks to months (or more), interfere with attempts to recover microbes through environmental sampling, and provide a mixed bacterial population for the horizontal transfer of resistance genes. The capacity of existing detergent formulations and disinfectants to disrupt biofilms may have an important and previously unrecognized role in determining their effectiveness in the field, which should be reflected in testing standards. There is a need for further research to elucidate the nature and physiology of microbes on dry hospital surfaces, specifically the prevalence and composition of biofilms. This will inform new approaches to hospital cleaning and disinfection, including novel surfaces that reduce microbial attachment and improve microbial detachment, and methods to augment the activity of biocides against surface-attached microbes such as bacteriophages and antimicrobial peptides. Future strategies to address environmental contamination on hospital surfaces should consider the presence of microbes attached to surfaces, including biofilms.
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Test methods for efficacy assessment of antimicrobial coatings are not modelled on a hospital environment, and instead use high humidity (>90%) high temperature (37 °C), and no airflow. Therefore, an inoculum will not dry, resulting in an antimicrobial surface exhibiting prolonged antimicrobial activity, as moisture is critical to activity. Liquids will dry quicker in a hospital ward, resulting in a reduced antimicrobial efficacy compared to the existing test, rendering the test results artificially favourable to the antimicrobial claim of the product. This study aimed to assess how hospital room environmental conditions can affect the drying time of an inoculum, and to use this data to inform test parameters for antimicrobial efficacy testing based on the hospital ward. The drying time of different droplet sizes, in a range of environmental conditions likely found in a hospital ward, were recorded (n = 630), and used to create a model to inform users of the experimental conditions required to provide a drying time similar to what can be expected in the hospital ward. Drying time data demonstrated significant (p < 0.05) variance when humidity, temperature, and airflow were assessed. A mathematical model was created to select environmental conditions for in vitro antimicrobial efficacy testing. Drying time in different environmental conditions demonstrates that experimental set-ups affect the amount of time an inoculum stays wet, which in turn may affect the efficacy of an antimicrobial surface. This should be an important consideration for hospitals and other potential users, whilst future tests predict efficacy in the intended end-use environment.
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Search for developing new antimicrobial polymers and designing new antimicrobial materials is an important research area to overcome bacterial resistance. In the present study a new polymer, poly(4–Vinyl–2–pyridone), having bioactive structure analogous to the naturally occurring heterocyclic compounds, was synthesized from 4–Vinylpyridine following a simple protocol. To augment the antibacterial properties of the synthesized polymer, N–alkylation of the heterocyclic pyridone moieties was achieved with ethylene chlorohydrin (2–Chloroethanol) to generate choline analogous structure. Also, its N–Butylated analogue was synthesized as a reference compound to study structure–activity relationship. Structure of the polymers was confirmed by different characterization techniques. Antimicrobial efficacy of the polymers was determined by minimum inhibitory concentration method in parallel experiments. The test microorganisms used were Gram (+) bacterium (Staphylococcus epidermidis), Gram (−) bacteria (Salmonella typhi, Pseudomonas aeruginosa and Escherichia coli) and fungus (Candida albicans). Both the polymer derivatives are far more effective antimicrobial agents than the pristine polymer. Trends in the antimicrobial efficacy of these polymers correlate with their zeta potential values.
Thesis
De nombreuses avancées ont été réalisées en termes de géométries instrumentales, mouvements de travail et procédés de fabrication des limes endodontiques. Cependant, peu de recherches se sont tournées vers l’utilisation d’alliages à mémoire de forme (AMF) autres que le Nickel-Titane (NiTi). Ce travail se propose de développer un instrument endodontique constitué d’un nouvel AMF aux propriétés mécaniques et antimicrobiennes très prometteuses : le CuAlBe monocristallin. Après une première analyse par éléments finis des paramètres géométriques adéquats pour une lime endodontique en AMF monocristallin à base de CuAlBe, plusieurs prototypes ont été fabriqués puis testés en rotation continue selon un protocole de pénétration / retrait (P/R) dans des canaux artificiels. Des limes endodontiques en NiTi, déjà commercialisées, ont été également testées avec le même protocole. L’objectif de ces recherches était de montrer que les instruments endodontiques en CuAlBe monocristallin présentaient des performances mécaniques équivalentes à ceux en NiTi, en plus de leurs propriétés antimicrobiennes
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A nano-bilayer structure consisting of copper and SnO2 nanocomposites was prepared by a magnetron sputtering method. A nano-SnO2 thin layer with a thickness of 52 nm was achieved on quartz glass. A nano-copper layer was then deposited on top of the SnO2 thin layer by the sputtering method. The thickness of the nano-copper layer was approximately 7 nm, such that the SnO2 layer was not only completely covered by the copper layer but it also resulted in transparent bilayer films. Post-annealing was carried out at 400°C in air for 1 h to obtain a crystalline SnO2 phase and simultaneously the copper layer was oxidized to CuO. Sputtered nanocomposites of CuO/SnO2 bilayer films showed a synergistic effect toward E. coli inactivation under indoor light exposure. A possible mechanism for the synergistic effect with respect to the antibacterial properties of CuO/SnO2 bilayer nanocomposites has been proposed. Incorporating CuO onto the SnO2 layer achieves photocatalyst works under indoor light and provides an antimicrobial function even under a dark environment by the antimicrobial property of CuO itself. Reported CuO/SnO2 sputter coating can be useful to apply, for instance, to electric devices such as touch panel displays in a hospital in order to reduce hospital-acquired infections (HAIs).
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Health care-associated infections (HAIs) are a global problem associated with significant morbidity and mortality. Controlling the spread of antimicrobial-resistant bacteria is a major public health challenge, and antimicrobial resistance has become one of the most important global problems in current times. The antimicrobial effect of copper has been known for centuries, and ongoing research is being conducted on the use of copper-coated hard and soft surfaces for reduction of microbial contamination and, subsequently, reduction of HAIs. This review provides an overview of the historical and current evidence of the antimicrobial and wound-healing properties of copper and explores its possible utility in obstetrics and gynecology.
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This study aimed to understand the efficacy and mechanisms of action of an aerosolised glycol-ethanol formulations against bacteria. We validated a small scale in-house test chamber to determine the microbicidal efficacy of four aerosolized formulations combining dipropylene glycol and ethanol against Staphylococcus aureus and Escherichia coli embedded in alginate. The aerosolised glycol/ethanol formulation decreased bacterial viability by 3 Log10 and was more efficacious than an ethanol only control formulation. Electron microscopic examination indicated extensive structural damage in both bacteria, and membrane damage was confirmed with potassium release in S. aureus and DNA release in E. coli. The development of a small test chamber facilitated the measurement of the microbicidal efficacy and experiments to understand the mechanism of action of an aerosolised microbicidal formulation.
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Background: The introduction of antimicrobial surfaces into healthcare environments is believed to impact positively on the rate of healthcare-associated infections by significantly decreasing pathogen presence on surfaces. Aim: To report on a novel efficacy test that uses a dry bacterial inoculum to measure the microbicidal efficacy of antimicrobial surfaces. Methods: An aerosolized dry inoculum of Staphylococcus aureus or Acinetobacter baumannii was deposited on copper alloy surfaces or a hospital-grade stainless-steel surface. Surviving bacteria were enumerated following incubation of the inoculated surfaces at an environmentally relevant temperature and relative humidity. Damage caused to bacteria by the aerosolization process and by the different surfaces was investigated. Findings: Dry inoculum testing showed a <2-log10 reduction in S. aureus or A. baumannii on the copper alloy surfaces tested after 24 h at 20°C and 40% relative humidity. Potential mechanisms of action included membrane damage, DNA damage and arrested cellular respiration. The aerosolization process caused some damage to bacterial cells. Once this effect was taken into account, the antimicrobial activity of copper surfaces was evident. Conclusions: Our test provided a realistic deposition of a bacterial inoculum to a surface and, as such, a realistic protocol to assess the efficacy of dry antimicrobial environmental surfaces in vitro.
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Shape Memory Alloys (SMAs) are widely used in endodontics as instruments for root canal preparation namely endodontic rotary files. Despite their high performances, compared to stainless steel instruments, it is still possible to enhance their cutting efficiency by acting on their shape and material properties. As an example, increasing the exhibited reversible martensitic transformation strain makes them more flexible without decreasing their mechanical strength. It becomes possible with single crystal SMAs. Cu-based (Cu-Al-Be, Cu-Zn-Al, Cu-Al-Mn) single crystal SMAs start emerging and can reach about 12% of martensitic transformation strain, in addition to their interesting antimicrobial properties. This study investigates, both numerically and experimentally, the development of endodontic files made of Cu-based single crystal SMAs. The numerical analysis is carried out by the finite element method. The geometry of the instrument is parameterized. Depending on the applied boundary conditions, bending, torsion, or combined bending-torsion loadings are represented.A micromechanical constitutive lawis implemented in Abaqus via the UMAT subroutine to describe the thermomechanical behavior of the Cu-basedsingle crystal SMA. Following the thus obtained numerical results, Coltene-Micromega company has manufactured endodontic file prototypes made of Cu-Al-Be single crystal SMA. A specific setup applying the same boundary conditions of torsion-bending loading, is used to characterize these SMA file prototypes. The good agreement between experimental and numerical responses, for a combined bending-torsion loading, proves the relevance of the proposed approach and the pertinence of considering Cu-based SMAs for endodontic file applications.
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Environmental surfaces and their role in the epidemiology of hospital-acquired infections (HAIs) have become an area of great scientific interest, particularly in light of the much publicised cases of infections due to methicillin-resistant Staphylococcus aureus (MRSA) and Clostridium difficile in UK hospitals. This feature article sets out to examine the role of surfaces and the inanimate environment in the spread of HAIs, and looks at various antimicrobial techniques being researched to reduce microbial contamination of surfaces. Preventative measures such as coatings which reduce initial microbial adhesion to surfaces will be considered alongside actively antimicrobial measures which inactivate microorganisms already adherent to a surface. The principal focus of this feature article will be given to light-activated antimicrobial surfaces such as the photocatalyst TiO2 and surfaces with embedded photosensitisers. Surfaces which release antimicrobial compounds or metal ions such as silver and copper are also examined, alongside materials which kill microbes upon contact. The widespread research and development of these antimicrobial surfaces is of great importance in maintaining acceptable levels of hygiene in hospitals and will help to fight the spread of HAIs via the contamination of inanimate surfaces in the healthcare environment.
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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.
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A new method for assessing bactericidal properties of metallic materials, soiled by aerosol, was developed and applied to stainless steel in conditions close to reality. The airborne bacteria survival on different stainless steel grades and massive copper is presented here. The investigating bacterium was Enterococcus faecalis, which is a well-known contaminant strain in the indoor environments. It was observed that the bacterial aerosol lethality increased proportionally with the relative humidity (RH) of the environment. A significant difference in survival rate was measured depending on the tested supports, the greatest lethality being observed on clean massive copper. Moreover, the addition of nutrients on metallic surfaces, even in small quantities, was enough to ensure the revival of quiescent microorganisms.
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Increasing numbers of hospital-acquired infections have generated much attention over the last decade. The public has linked the so-called 'superbugs' with their experience of dirty hospitals, but the precise role of cleaning in the control of these organisms in unknown. Hence the importance of a clean environment is likely to remain speculative unless it becomes an evidence-based science. This proposal is a call for bacteriological standards with which to assess clinical surface hygiene in hospitals, based on those used by the food industry. The first standard concerns any finding of a specific 'indicator' organism, the presence of which suggests a requirement for increased cleaning. Indicators would include Staphylococcus aureus, including methicillin-resistant S. aureus, Clostridium difficile, vancomycin-resistant enterococci and various Gram-negative bacilli. The second standard concerns a quantitative aerobic colony count of <5 cfu/cm(2) on frequent hand touch surfaces in hospitals. The principle relates to modern risk management systems such as HACCP, and reflects the fact that pathogens of concern are widespread. Further work is required to evaluate and refine these standards and define the infection risk from the hospital environment.
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Inanimate surfaces have often been described as the source for outbreaks of nosocomial infections. The aim of this review is to summarize data on the persistence of different nosocomial pathogens on inanimate surfaces. The literature was systematically reviewed in MedLine without language restrictions. In addition, cited articles in a report were assessed and standard textbooks on the topic were reviewed. All reports with experimental evidence on the duration of persistence of a nosocomial pathogen on any type of surface were included. Most gram-positive bacteria, such as Enterococcus spp. (including VRE), Staphylococcus aureus (including MRSA), or Streptococcus pyogenes, survive for months on dry surfaces. Many gram-negative species, such as Acinetobacter spp., Escherichia coli, Klebsiella spp., Pseudomonas aeruginosa, Serratia marcescens, or Shigella spp., can also survive for months. A few others, such as Bordetella pertussis, Haemophilus influenzae, Proteus vulgaris, or Vibrio cholerae, however, persist only for days. Mycobacteria, including Mycobacterium tuberculosis, and spore-forming bacteria, including Clostridium difficile, can also survive for months on surfaces. Candida albicans as the most important nosocomial fungal pathogen can survive up to 4 months on surfaces. Persistence of other yeasts, such as Torulopsis glabrata, was described to be similar (5 months) or shorter (Candida parapsilosis, 14 days). Most viruses from the respiratory tract, such as corona, coxsackie, influenza, SARS or rhino virus, can persist on surfaces for a few days. Viruses from the gastrointestinal tract, such as astrovirus, HAV, polio- or rota virus, persist for approximately 2 months. Blood-borne viruses, such as HBV or HIV, can persist for more than one week. Herpes viruses, such as CMV or HSV type 1 and 2, have been shown to persist from only a few hours up to 7 days. The most common nosocomial pathogens may well survive or persist on surfaces for months and can thereby be a continuous source of transmission if no regular preventive surface disinfection is performed.
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Biocides are heavily used in the healthcare environment, mainly for the disinfection of surfaces, water, equipment, and antisepsis, but also for the sterilization of medical devices and preservation of pharmaceutical and medicinal products. The number of biocidal products for such usage continuously increases along with the number of applications, although some are prone to controversies. There are hundreds of products containing low concentrations of biocides, including various fabrics such as linen, curtains, mattresses, and mops that claim to help control infection, although evidence has not been evaluated in practice. Concurrently, the incidence of hospital-associated infections (HAIs) caused notably by bacterial pathogens such as methicillin-resistant Staphylococcus aureus (MRSA) remains high. The intensive use of biocides is the subject of current debate. Some professionals would like to see an increase in their use throughout hospitals, whereas others call for a restriction in their usage to where the risk of pathogen transmission to patients is high. In addition, the possible linkage between biocide and antibiotic resistance in bacteria and the role of biocides in the emergence of such resistance has provided more controversies in their extensive and indiscriminate usage. When used appropriately, biocidal products have a very important role to play in the control of HAIs. This paper discusses the benefits and problems associated with the use of biocides in the healthcare environment and provides a constructive view on their overall usefulness in the hospital setting.
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The antimicrobial effect of copper has long been recognized and has a potential application in the healthcare setting as a mechanism to reduce environmental contamination and thus prevent healthcare-associated infection (HCAI). To review the rationale for copper use, the mechanism of its antimicrobial effect, and the evidence for its efficacy. A PubMed search of the published literature was performed. Extensive laboratory investigations have been carried out to investigate the biocidal activity of copper incorporated into contact surfaces and when impregnated into textiles and liquids. A limited number of clinical trials have been performed, which, although promising, leave significant questions unanswered. In particular there is a lack of consensus on minimum percentage copper alloys required for effectiveness, the impact of organic soiling on the biocidal effect of copper, and the best approach to routine cleaning of such surfaces. Limited information is available on the ability of copper surfaces to eradicate spores of Clostridium difficile. Additional studies to demonstrate that installing copper surfaces reduces the incidence of HCAI are required and the cost-effectiveness of such intervention needs to be assessed. Further research in a number of key areas is required before the potential benefits of using copper routinely in the clinical setting to prevent and control infection can be confirmed and recommended.
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The environment may act as a reservoir for pathogens that cause healthcare-associated infections (HCAIs). Approaches to reducing environmental microbial contamination in addition to cleaning are thus worthy of consideration. Copper is well recognised as having antimicrobial activity but this property has not been applied to the clinical setting. We explored its use in a novel cross-over study on an acute medical ward. A toilet seat, set of tap handles and a ward entrance door push plate each containing copper were sampled for the presence of micro-organisms and compared to equivalent standard, non-copper-containing items on the same ward. Items were sampled once weekly for 10 weeks at 07:00 and 17:00. After five weeks, the copper-containing and non-copper-containing items were interchanged. The total aerobic microbial counts per cm(2) including the presence of 'indicator micro-organisms' were determined. Median numbers of microorganisms harboured by the copper-containing items were between 90% and 100% lower than their control equivalents at both 07:00 and 17:00. This reached statistical significance for each item with one exception. Based on the median total aerobic cfu counts from the study period, five out of ten control sample points and zero out of ten copper points failed proposed benchmark values of a total aerobic count of <5cfu/cm(2). All indicator micro-organisms were only isolated from control items with the exception of one item during one week. The use of copper-containing materials for surfaces in the hospital environment may therefore be a valuable adjunct for the prevention of HCAIs and requires further evaluation.
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The practical importance and frequency of airborne nosocomial infections has been a matter of dispute for many years. This is because most of the pathogens acquired in hospitals are able to use various different routes of infecting the patient's body so that it may be difficult or even impossible to prove an individual infection to be airborne. Only microbes such as Streptococcus pyogenes, Neisseria meningitidis, Corynebacterium diphtheriae, Mycobacterium tuberculosis, or certain respiratory viruses that are known to be predominantly transmitted by droplet infection from infected persons or healthy carriers, have been accepted to the cause of airborne nosocomial infections. Other pathogens such as legionellae, pseudomonads or clostridia may be distributed in the hospital environment via an insufficient or defective air-conditioning system, with or without humidification. The assessment of indirect airborne infections caused by infective particles derived from dust which has settled on furniture or the floor or which has been introduced to the hospital environment by shoes, open windows, building works or potted indoor plants is much more difficult. Many Gram-positive bacteria such as Staphylococcus aureus, mycobacteria, nocardiae, and endospores of clostridia and bacilli, as well as the reproductive elements of fungi do remain viable and infective in dry dust and may therefore infect patients when the dust is disturbed. In contrast to nosocomial infections due to Gram-negative bacteria, against which most preventive measures have been concentrated in the past and which are usually not airborne in origin, it appears that the possibility of direct or indirect transmission of hospital pathogens by air has been underestimated.(ABSTRACT TRUNCATED AT 250 WORDS)
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To study the possible role of contaminated environmental surfaces as a reservoir of methicillin-resistant Staphylococcus aureus (MRSA) in hospitals. A prospective culture survey of inanimate objects in the rooms of patients with MRSA. A 200-bed university-affiliated teaching hospital. Thirty-eight consecutive patients colonized or infected with MRSA. Patients represented endemic MRSA cases. Ninety-six (27%) of 350 surfaces sampled in the rooms of affected patients were contaminated with MRSA. When patients had MRSA in a wound or urine, 36% of surfaces were contaminated. In contrast, when MRSA was isolated from other body sites, only 6% of surfaces were contaminated (odds ratio, 8.8; 95% confidence interval, 3.7-25.5; P < .0001). Environmental contamination occurred in the rooms of 73% of infected patients and 69% of colonized patients. Frequently contaminated objects included the floor, bed linens, the patient's gown, overbed tables, and blood pressure cuffs. Sixty-five percent of nurses who had performed morning patient-care activities on patients with MRSA in a wound or urine contaminated their nursing uniforms or gowns with MRSA. Forty-two percent of personnel who had no direct contact with such patients, but had touched contaminated surfaces, contaminated their gloves with MRSA. We concluded that inanimate surfaces near affected patients commonly become contaminated with MRSA and that the frequency of contamination is affected by the body site at which patients are colonized or infected. That personnel may contaminate their gloves (or possibly their hands) by touching such surfaces suggests that contaminated environmental surfaces may serve as a reservoir of MRSA in hospitals.
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Assessment of strategies for engineering controls for the prevention of airborne infectious disease transmission to patients and to health care and related workers requires consideration of the factors relevant to aerosol characterization. These factors include aerosol generation, particle size and concentrations, organism viability, infectivity and virulence, airflow and climate, and environmental sampling and analysis. The major focus on attention to engineering controls comes from recent increases in tuberculosis, particularly the multidrug-resistant varieties in the general hospital population, the severely immunocompromised, and those in at-risk and confined environments such as prisons, long-term care facilities, and shelters for the homeless. Many workers are in close contact with persons who have active, undiagnosed, or insufficiently treated tuberculosis. Additionally, patients and health care workers may be exposed to a variety of pathogenic human viruses, opportunistic fungi, and bacteria. This report therefore focuses on the nature of infectious aerosol transmission in an attempt to determine which factors can be systematically addressed to result in proven, applied engineering approaches to the control of infectious aerosols in hospital and health care facility environments. The infectious aerosols of consideration are those that are generated as particles of respirable size by both human and environmental sources and that have the capability of remaining viable and airborne for extended periods in the indoor environment. This definition precludes skin and mucous membrane exposures occurring from splashes (rather than true aerosols) of blood or body fluids containing infectious disease agents. There are no epidemiologic or laboratory studies documenting the transmission of bloodborne virus by way of aerosols.
Article
Aerosols containing microbes from the oral cavity of the patient are created when using modern high-speed rotating instruments in restorative dentistry. How far these aerosols spread and what level of contamination they cause in the dental surgery has become a growing concern as the number of patients with oro-nasal meticillin-resistant Staphylococcus aureus colonization has increased. The present study aimed to determine how far airborne bacteria spread during dental treatment, and the level of contamination. Fall out samples were collected on blood agar plates placed in six different sectors, 0.5-2m from the patient. Restorative dentistry fallout samples (N=72) were collected from rooms (N=6) where high-speed rotating instruments were used, and control samples (N=24) were collected from rooms (N=4) used for periodontal and orthodontic treatment where rotating and ultrasonic instruments were not used. The collection times were 1.5 and 3 h. In addition, samples were taken from facial masks of personnel and from surfaces in the rooms before and after disinfection. After 48 h of incubation at 37 degrees C, colonies were counted and classified by Gram stain. The results showed significant contamination of the room at all distances sampled when high-speed instruments were used (mean 970 colony-forming units/m2/h). The bacterial density was found to be higher in the more remote sampling points. Gram-positive cocci, namely viridans streptococci and staphylococci, were the most common findings. The area that becomes contaminated during dental procedures is far larger than previously thought and practically encompasses the whole room. These results emphasize the need for developing new means for preventing microbial aerosols in dentistry and protection of all items stored temporarily on work surfaces. This is especially important when treating generally ill or immunocompromised patients at dental surgeries in hospital environments.
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Persistent contamination of surfaces by spores of Clostridium difficile is a major factor influencing the spread of C. difficile-associated diarrhoea (CDAD) in the clinical setting. In recent years, the antimicrobial efficacy of metal surfaces has been investigated against microorganisms including methicillin-resistant Staphylococcus aureus. This study compared the survival of C. difficile on stainless steel, a metal contact surface widely used in hospitals, and copper surfaces. Antimicrobial efficacy was assessed using a carrier test method against dormant spores, germinating spores and vegetative cells of C. difficile (NCTC 11204 and ribotype 027) over a 3 h period in the presence and absence of organic matter. Copper metal eliminated all vegetative cells of C. difficile within 30 min, compared with stainless steel which demonstrated no antimicrobial activity (P < 0.05). Copper significantly reduced the viability of spores of C. difficile exposed to the germinant (sodium taurocholate) in aerobic conditions within 60 min (P < 0.05) while achieving a >or=2.5 log reduction (99.8% reduction) at 3 h. Organic material did not reduce the antimicrobial efficacy of the copper surface (P > 0.05). The use of copper surfaces within the clinical environment and application of a germination solution in infection control procedures may offer a novel way forward in eliminating C. difficile from contaminated surfaces and reducing CDAD.
How do we assess hospital cleaning? A proposal for microbiological standards for surface hygiene in hospitals.
  • Dancer S.J.