Copper alloy surfaces sustain terminal cleaning levels in a rural hospital

Efficacy of copper blend coatings in reducing SARS-CoV-2 contamination

SARS-CoV-2 is a highly infectious virus and etiologic agent of COVID-19, which is spread by respiratory droplets, aerosols, and contaminated surfaces. Copper is a known antiviral agent, and has resulted in successful reduction of pathogens and infections by 83-99.9% when coated on surfaces in intensive care units. Additionally, copper has been shown to inactivate pathogens such as Coronavirus 226E, a close relative of SARS-CoV-2. Here, we examine the ability of two copper blends with differing compositions to inactivate SARS-CoV-2 virus at different time points. Copper Blend 2 (75.07% pure copper) was found to significantly reduce (over 50%) the viability of SARS-CoV-2 at 5 min of contact, with at least 98% reduction in recovered virus at 20 min (vs. plastic control). However, Copper Blend 1 (48.26% pure copper), was not found to significantly reduce viability of SARS-CoV-2 at any time point when compared to plastic. This may indicate that there is an important percentage of copper content in materials that is needed to effectively inactivate SARS-CoV-2. Overall, this study shows that over the course of 20 min, coatings made of copper materials can significantly reduce the recovery of infectious SARS-CoV-2 compared to uncoated controls, indicating the effective use of copper for viral inactivation on surfaces. Furthermore, it may suggest higher copper content has stronger antiviral properties. This could have important implications when short turnaround times are needed for cleaning and disinfecting rooms or equipment, especially in strained healthcare settings which are struggling to keep up with demand.

The Comparative Performance of Phytochemicals, Green Synthesised Silver Nanoparticles, and Green Synthesised Copper Nanoparticles-Loaded Textiles to Avoid Nosocomial Infections

In the current study, a sustainable approach was adopted for the green synthesis of silver nanoparticles, green synthesis of copper nanoparticles, and the investigation of the phytochemical and biological screening of bark, leaves, and fruits of Ehretia acuminata (belongs to the family Boraginaceae). Subsequently, the prepared nanoparticles and extracted phytochemicals were loaded on cotton fibres. Surface morphology, size, and the presence of antimicrobial agents (phytochemicals and particles) were analysed by scanning electron microscopy, dynamic light scattering, and energy-dispersive X-ray spectroscopy. The functional groups and the presence of particles (copper and silver) were found by FTIR and XRD analyses. The coated cotton fibres were further investigated for antibacterial (qualitative and quantitative), antiviral, and antifungal analysis. The study revealed that the herb-encapsulated nanoparticles can be used in numerous applications in the field of medical textiles. Furthermore, the utility of hygienic and pathogenic developed cotton bandages was analysed for the comfort properties regarding air permeability and water vapour permeability. Finally, the durability of the coating was confirmed by measuring the antibacterial properties after severe washing.

Chemical Nature of Metals and Metal-Based Materials in Inactivation of Viruses

In response to the enormous threat to human survival and development caused by the large number of viruses, it is necessary to strengthen the defense against and elimination of viruses. Metallic materials have been used against viruses for thousands of years due to their broad-spectrum antiviral properties, wide sources and excellent physicochemical properties; in particular, metal nanoparticles have advanced biomedical research. However, researchers in different fields hold dissimilar views on the antiviral mechanisms, which has slowed down the antiviral application of metal nanoparticles. As such, this review begins with an exhaustive compilation of previously published work on the antiviral capacity of metal nanoparticles and other materials. Afterwards, the discussion is centered on the antiviral mechanisms of metal nanoparticles at the biological and physicochemical levels. Emphasis is placed on the fact that the strong reducibility of metal nanoparticles may be the main reason for their efficient inactivation of viruses. We hope that this review will benefit the promotion of metal nanoparticles in the antiviral field and expedite the construction of a barrier between humans and viruses.

Experimental Evolution of Copper Resistance in Escherichia coli Produces Evolutionary Trade-Offs in the Antibiotics Chloramphenicol, Bacitracin, and Sulfonamide

The rise in antimicrobial resistant bacteria have prompted the need for antibiotic alternatives. To address this problem, significant attention has been given to the antimicrobial use and novel applications of copper. As novel applications of antimicrobial copper increase, it is important to investigate how bacteria may adapt to copper over time. Here, we used experimental evolution with re-sequencing (EER-seq) and RNA-sequencing to study the evolution of copper resistance in Escherichia coli. Subsequently, we tested whether copper resistance led to rifampicin, chloramphenicol, bacitracin, and/or sulfonamide resistance. Our results demonstrate that E. coli is capable of rapidly evolving resistance to CuSO₄ after 37 days of selection. We also identified multiple de novo mutations and differential gene expression patterns associated with copper, most notably those mutations identified in the cpx gene. Furthermore, we found that the copper resistant bacteria had decreased sensitivity when compared to the ancestors in the presence of chloramphenicol, bacitracin, and sulfonamide. Our data suggest that the selection of copper resistance may inhibit growth in the antimicrobials tested, resulting in evolutionary trade-offs. The results of our study may have important implications as we consider the antimicrobial use of copper and how bacteria may respond to increased use over time.

Evidence Map and Systematic Review of Disinfection Efficacy on Environmental Surfaces in Healthcare Facilities

Healthcare-associated infections (HAIs) contribute to patient morbidity and mortality with an estimated 1.7 million infections and 99,000 deaths costing USD $28-34 billion annually in the United States alone. There is little understanding as to if current environmental surface disinfection practices reduce pathogen load, and subsequently HAIs, in critical care settings. This evidence map includes a systematic review on the efficacy of disinfecting environmental surfaces in healthcare facilities. We screened 17,064 abstracts, 635 full texts, and included 181 articles for data extraction and study quality assessment. We reviewed ten disinfectant types and compared disinfectants with respect to study design, outcome organism, and fourteen indictors of study quality. We found important areas for improvement and gaps in the research related to study design, implementation, and analysis. Implementation of disinfection, a determinant of disinfection outcomes, was not measured in most studies and few studies assessed fungi or viruses. Assessing and comparing disinfection efficacy was impeded by study heterogeneity; however, we catalogued the outcomes and results for each disinfection type. We concluded that guidelines for disinfectant use are primarily based on laboratory data rather than a systematic review of in situ disinfection efficacy. It is critically important for practitioners and researchers to consider system-level efficacy and not just the efficacy of the disinfectant.

Can Copper Products and Surfaces Reduce the Spread of Infectious Microorganisms and Hospital-Acquired Infections?

Pathogen transfer and infection in the built environment are globally significant events, leading to the spread of disease and an increase in subsequent morbidity and mortality rates. There are numerous strategies followed in healthcare facilities to minimize pathogen transfer, but complete infection control has not, as yet, been achieved. However, based on traditional use in many cultures, the introduction of copper products and surfaces to significantly and positively retard pathogen transmission invites further investigation. For example, many microbes are rendered unviable upon contact exposure to copper or copper alloys, either immediately or within a short time. In addition, many disease-causing bacteria such as E. coli O157:H7, hospital superbugs, and several viruses (including SARS-CoV-2) are also susceptible to exposure to copper surfaces. It is thus suggested that replacing common touch surfaces in healthcare facilities, food industries, and public places (including public transport) with copper or alloys of copper may substantially contribute to limiting transmission. Subsequent hospital admissions and mortality rates will consequently be lowered, with a concomitant saving of lives and considerable levels of resources. This consideration is very significant in times of the COVID-19 pandemic and the upcoming epidemics, as it is becoming clear that all forms of possible infection control measures should be practiced in order to protect community well-being and promote healthy outcomes.

Brass Alloys: Copper-Bottomed Solutions against Hospital-Acquired Infections?

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.

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

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

Development of Antimicrobial Multifunctional Textiles to Avoid from Hospital-Acquired Infections

The objectives of the present study were to develop the environmental friendly, low price, easy and fast method for developing the antibacterial cuprous oxide coated multifunctional fabrics. At first, fabrics were sensitized with citric acid then the formation of Cu₂O particles was done by Fehling solution method. In second step, the cuprous oxide particles were deposited on cotton fabrics. Three different types of reducing agents with different concentrations were selected to make the Cu₂O particles. Surface morphology and presence of metals were analysed by scanning electron microscopy, dynamic light scattering, FTIR, EDS and XRD. The antibacterial activity of cuprous oxide coated fabrics was tested against qualitative and quantitative measurements. The strongest antibacterial effect was found for the fabrics coated with cuprous oxide particles reduced with sodium hydrosulphite at 1 g/l. Furthermore, the utility of hygienic antimicrobial developed fabrics were analysed for the comfort properties regarding air permeability and stiffness. At the end, durability of coating was confirmed by measuring the antibacterial properties and SEM analysis after washing.

Self-Disinfecting Copper Beds Sustain Terminal Cleaning and Disinfection Effects throughout Patient Care

Microbial burden associated with near-patient touch surfaces results in a greater risk of health care-associated infections (HAIs). Acute care beds may be a critical fomite, as traditional plastic surfaces harbor the highest concentrations of bacteria associated with high-touch surfaces in a hospital room's patient zone. Five high-touch intensive care unit (ICU) bed surfaces encountered by patients, health care workers, and visitors were monitored by routine culture to assess the effect U.S. Environmental Protection Agency (U.S. EPA)-registered antimicrobial copper materials have on the microbial burden. Despite both daily and discharge cleaning and disinfection, each control bed's plastic surfaces exceeded bacterial concentrations recommended subsequent to terminal cleaning and disinfection (TC&D) of 2.5 aerobic CFU/cm² Beds with self-disinfecting (copper) surfaces harbored significantly fewer bacteria throughout the patient stay than control beds, at levels below those considered to increase the likelihood of HAIs. With adherence to routine daily and terminal cleaning regimes throughout the study, the copper alloy surfaces neither tarnished nor required additional cleaning or special maintenance. Beds encapsulated with U.S. EPA-registered antimicrobial copper materials were found to sustain the microbial burden below the TC&D risk threshold levels throughout the patient stay, suggesting that outfitting acute care beds with such materials may be an important supplement to controlling the concentration of infectious agents and thereby potentially reducing the overall HAI risk.IMPORTANCE Despite cleaning efforts of environmental service teams and substantial compliance with hand hygiene best practices, the microbial burden in patient care settings often exceeds concentrations at which transfer to patients represents a substantial acquisition risk for health care-associated infections (HAIs). Approaches to limit HAI risk have relied on designing health care equipment and furnishings that are easier to clean and/or the use of no-touch disinfection interventions such as germicidal UV irradiation or vapor deposition of hydrogen peroxide. In a clinical trial evaluating the largest fomite in the patient care setting, the bed, a bed was encapsulated with continuously disinfecting antimicrobial copper surfaces, which reduced the bacteria on surfaces by 94% and sustained the microbial burden below the terminal cleaning and disinfection risk threshold throughout the patient's stay. Such an intervention, which continuously limits microbes on high-touch surfaces, should be studied in a broader range of health care settings to determine its potential long-range efficacy for reducing HAI.

In situ evaluation of a persistent disinfectant provides continuous decontamination within the clinical environment

Microbial bioburden associated with the built environment can impact the rate of health care-associated infection acquisition; higher bioburden results in a greater incidence of health care-associated infections. Two disinfectants registered by the US Environmental Protection Agency and a trial disinfectant were evaluated for their ability to limit the establishment of bioburden subsequent to application under in situ conditions on patient bed rails within a medical intensive care unit. Bioburden samples were collected immediately prior to disinfection and at 1, 6, and 24 hours after application. The trial disinfectant was engineered to provide continuous disinfection over a 24-hour period. Each disinfectant was able to significantly control bioburden for the first hour. In comparison, the persistent agent was found superior for all time points when compared to a dilutable quaternary ammonium agent, and it was significantly better for controlling bioburden for 2 of the 3 times points for the disinfectant with ethanol and quaternary ammonium as its agent.

Continuous room decontamination technologies

The contaminated surface environment in the rooms of hospitalized patients is an important risk factor for the colonization and infection of patients with multidrug-resistant pathogens. Improved terminal cleaning and disinfection have been demonstrated to reduce the incidence of health care-associated infections. In the United States, hospitals generally perform daily cleaning and disinfection of patient rooms. However, cleaning and disinfection are limited by the presence of the patient in room (eg, current ultraviolet devices and hydrogen peroxide systems cannot be used) and the fact that after disinfection pathogenic bacteria rapidly recolonize surfaces and medical devices/equipment. For this reason, there has been great interest in developing methods of continuous room disinfection and/or "self-disinfecting" surfaces. This study will review the research on self-disinfecting surfaces (eg, copper-coated surfaces and persistent chemical disinfectants) and potential new room disinfection methods (eg, "blue light" and diluted hydrogen peroxide systems).

Copper for the Prevention of Outbreaks of Health Care-Associated Infections in a Long-term Care Facility for Older Adults

OBJECTIVE

We aimed to study the efficacy of copper as an antimicrobial agent by comparing incidence rates during outbreaks in areas equipped vs not equipped with copper surfaces in a long-term facility for dependent older adults (nursing home).

DESIGN

Prospective observational pilot study in a nursing home.

SETTING AND PARTICIPANT

All persons resident in the nursing home belonging to Reims University Hospital, from February 1, 2015 to June 30, 2016, were included.

METHODS

Incidence rates for health care-related infections during outbreaks occurring during the study period were compared between the wing that was equipped and the wing that was not equipped with copper surfaces. Results are expressed as relative risks (RRs) and 95% confidence intervals (95% CIs).

RESULTS

During the study period, 556 residents were included; average age was 85.4 ± 9.2 years, and 76% were women. Four outbreaks occurred during the study period: 1 influenza, 1 keratoconjunctivitis, and 2 gastroenteritis outbreaks. The risk of hand-transmitted health care-associated infection was significantly lower in the area equipped with copper surfaces (RR 0.3, 95% CI 0.1-0.5).

CONCLUSIONS AND IMPLICATIONS

In our study, copper was shown to reduce the incidence of hand-transmitted health care-associated infections and could represent a relatively simple measure to help prevent HAIs in nursing homes.

Proteome profiling of Pseudomonas aeruginosa PAO1 identifies novel responders to copper stress

BACKGROUND

The opportunistic pathogen, Pseudomonas aeruginosa is well known for its environmental and metabolic versatility, yet many of the functions of its gene-products remain to be fully elucidated. This study's objective was to illuminate the potential functions of under-described gene-products during the medically relevant copper-stress condition.

RESULTS

We used data-independent acquisition mass spectrometry to quantitate protein expression changes associated with copper stress in P. aeruginosa PAO1. Approximately 2000 non-redundant proteins were quantified, with 78 proteins altering in abundance by +/- 1.5-fold or more when cultured to mid-log growth in the presence of 50 μM copper sulfate. One-third of those differentially expressed proteins have no prior established functional roles.

CONCLUSIONS

This study provides evidence for the functional involvement of some specific proteins in enabling P. aeruginosa to survive under sub-lethal concentrations of copper. This further paves the way for targeted investigations into the specific mechanisms of their activity.

Antimicrobial properties of a novel copper-based composite coating with potential for use in healthcare facilities

Background

Healthcare-associated infections (HAIs) have a major impact on public health worldwide. Particularly, hospital surfaces contaminated with bacterial pathogens are often the origin of both sporadic cases and outbreaks of HAIs. It has been demonstrated that copper surfaces reduce the microbial burden of high touch surfaces in the hospital environment. Here we report the antimicrobial characterization of a novel composite coating with embedded copper particles, named Copper Armour™.

Methods

The Copper Armour™ bactericidal activity was evaluated in in vitro assays against several bacterial pathogens, including Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli O157:H7 and Listeria monocytogenes. Additionally, its antimicrobial properties were also evaluated in a pilot study over a nine-week period at an adult intensive care unit. For this, four high touch surfaces, including bed rails, overbed table, bedside table and IV Pole, were coated with Cooper Armour™, and its microbial burden was determined over a nine-week period.

Results

Copper Armour™ coated samples showed an in vitro reduction in bacterial burden of > 99.9% compared to control samples. Moreover, pilot study results indicate that Copper Armour™ significantly reduces the level of microbial contamination on high-touch surfaces in the hospital environment, as compared with standard surfaces.

Conclusions

Based on its antimicrobial properties, Copper Armour™ is a novel self-sanitizing coating that exhibits bactericidal activity against important human pathogens and significantly reduces the microbial burden of hospital surfaces. This composite could be used as a self-sanitizing coating to complement infection control strategies in healthcare facilities.

Copper Alloy Touch Surfaces in Healthcare Facilities: An Effective Solution to Prevent Bacterial Spreading

In the healthcare environment, microorganisms' cross-transmission between inanimate surfaces and patients or healthcare workers can lead to healthcare-associated infections. A recent interest has grown to create antimicrobial copper touch surfaces, in order to counteract microbial spread in the healthcare environment. For the first time, five French long-term care facilities were at 50% fitted with copper alloys door handles and handrails. Related to the environmental bacterial contamination, 1400 samples were carried out on copper and control surfaces over three years after copper installation. In addition, some copper door handles were taken from the different facilities, and their specific activity against methicillin-resistant S. aureus (MRSA) was tested in vitro. In comparison to control surfaces, copper door handles and handrails revealed significantly lower contamination levels. This difference was observed in the five long-term care facilities and it persists through the three years of the study. High and extreme levels of bacterial contamination were less frequent on copper surfaces. Although, the antibacterial activity of copper surfaces against MRSA was lowered after three years of regular use, it was still significant as compared to inert control surfaces. Therefore, copper containing surfaces are promising actors in the non-spreading of environmental bacterial contamination in healthcare facilities.

Novel Antibacterials: Alternatives to Traditional Antibiotics

With the advent of the global antimicrobial resistance (AMR) crisis, our arsenal of effective antibiotics is diminishing. The widespread use and misuse of antibiotics in human and veterinary medicine, compounded by the lack of novel classes of antibiotic in the pharmaceutical pipeline, has left a hole in our antibiotic armamentarium. Thus, alternatives to traditional antibiotics are being investigated, including two major groups of antibacterial agents, which have been extensively studied, phytochemicals and metals. Within these groups, there are several subclasses of compound/elements, including polyphenols and metal nanoparticles, which could be used to complement traditional antibiotics, either to increase their potency or extend their spectrum of activity. Alone or in combination, these antibacterial agents have been shown to be effective against a vast array of human and animal bacterial pathogens, including those resistant to licensed antibacterials. These alternative antibacterial agents could be a key element in our fight against AMR and provide desperately needed options, to veterinary and medical clinicians alike.

Reduction of bacterial burden by copper alloys on high-touch athletic center surfaces

BACKGROUND

Athletic centers have been locations for the transmission of community-acquired infections. This study assessed the capacity of copper alloys to reduce the bacterial burden associated with high-touch athletic center equipment. Copper alloy weights and grips were rotated with rubber coated and stainless steel controls in an undergraduate college athletic center over a 16-month period. The athletic center is used by college athletic teams, student body, and local community.

METHODS

The primary outcome was to compare bacterial burdens on copper and control grips by swabbing surfaces. Significance was determined using the nonparametric Mann-Whitney U test with significance assessed at P < .05. Secondary outcomes included characterizing bacterial communities on surfaces and conducting antibiotic susceptibility testing using the Kirby-Bauer disk diffusion method.

RESULTS

Control athletic center components carried bacterial loads 94% larger than those found on copper alloy components. Bacterial community characterization revealed Staphylococcus to be the most common bacterial genus found on grip surfaces. Antibiotic resistance testing of the Staphylococcus isolates revealed that all isolates were susceptible to vancomycin and linezolid, whereas 35% of copper alloy isolates and 44% of control isolates were resistant to erythromycin.

CONCLUSIONS

Copper alloys can mitigate the bacterial burden on high-touch surfaces. Strategically placing copper alloys in areas of high human contact can augment infection control efforts and potentially decrease community-acquired infections in athletic centers.

Reduction of Environmental Contamination With Multidrug-Resistant Bacteria by Copper-Alloy Coating of Surfaces in a Highly Endemic Setting

OBJECTIVE To evaluate the efficacy of copper-coating in reducing environmental colonization in an intensive-care unit (ICU) with multidrug-resistant-organism (MDRO) endemicity DESIGN Interventional, comparative crossover trial SETTING The general ICU of Attikon University hospital in Athens, Greece PATIENTS Those admitted to ICU compartments A and B during the study period METHODS Before any intervention (phase 1), the optimum sampling method using 2 nylon swabs was validated. In phase 2, 6 copper-coated beds (ie, with coated upper, lower, and side rails) and accessories (ie, coated side table, intravenous [i.v.] pole stands, side-cart handles, and manual antiseptic dispenser cover) were introduced as follows: During phase 2a (September 2011 to February 2012), coated items were placed next to noncoated ones (controls) in both compartments A and B; during phase 2b (May 2012 to January 2013), all copper-coated items were placed in compartment A, and all noncoated ones (controls) in compartment B. Patients were randomly assigned to available beds. Environmental samples were cultured quantitatively for clinically important bacteria. Clinical and demographic data were collected from medical records. RESULTS Copper coating significantly reduced the percentage of colonized surfaces (55.6% vs 72.5%; P<.0001), the percentage of surfaces colonized by MDR gram-negative bacteria (13.8% vs 22.7%; P=.003) or by enterococci (4% vs 17%; P=.014), the total bioburden (2,858 vs 7,631 cfu/100 cm2; P=.008), and the bioburden of gram-negative isolates, specifically (261 vs 1,266 cfu/100 cm2; P=.049). This effect was more pronounced when the ratio of coated surfaces around the patient was increased (phase 2b). CONCLUSIONS Copper-coated items in an ICU setting with endemic high antimicrobial resistance reduced environmental colonization by MDROs. Infect Control Hosp Epidemiol 2017;38:765-771.

The Role of Intermetal Competition and Mis-Metalation in Metal Toxicity

The metals manganese, iron, cobalt, nickel, copper and zinc are essential for almost all bacteria, but their precise metal requirements vary by species, by ecological niche and by growth condition. Bacteria thus must acquire each of these essential elements in sufficient quantity to satisfy their cellular demand, but in excess these same elements are toxic. Metal toxicity has been exploited by humanity for centuries, and by the mammalian immune system for far longer, yet the mechanisms by which these elements cause toxicity to bacteria are not fully understood. There has been a resurgence of interest in metal toxicity in recent decades due to the problematic spread of antibiotic resistance amongst bacterial pathogens, which has led to an increased research effort to understand these toxicity mechanisms at the molecular level. A recurring theme from these studies is the role of intermetal competition in bacterial metal toxicity. In this review, we first survey biological metal usage and introduce some fundamental chemical concepts that are important for understanding bacterial metal usage and toxicity. Then we introduce a simple model by which to understand bacterial metal homeostasis in terms of the distribution of each essential metal ion within cellular 'pools', and dissect how these pools interact with each other and with key proteins of bacterial metal homeostasis. Finally, using a number of key examples from the recent literature, we look at specific metal toxicity mechanisms in model bacteria, demonstrating the role of metal-metal competition in the toxicity mechanisms of diverse essential metals.