Peer-reviewed research papers discussing the antimicrobial property of copper-based metals
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Christophe Espírito Santo, Davide Quaranta, Gregor Grass -
http://onlinelibrary.wiley.com/doi/10.1002/mbo3.2/full
Molecular knowledge of the mode-of-action exerted by metallic Cu
on microbes is certainly not strictly necessary for widespread
application of antimicrobial surfaces in hygiene-sensitive areas.
Currently, it is agreed-upon that genomic material will eventually
degrade on metallic Cu (Weaver et al. 2011; Warnes and Keevil
2010; Espirito Santo
and Grass, unpublished observations) but it is controversial if
this process is causative for or subsequent to cell death (Weaver
et al. 2010; Espirito Santo et
al. 2011). We propose that
current data favor the model that membranes are damaged first,
causing lethality, followed by protein oxidation (Nandakumar et al.
2011) and
DNA-degradation. In depth understanding of the sensitive cellular
targets of Cu toxicity and the order of events leading to death,
however, can be expected to provide new opportunities for improving
the efficacy of Cu surfaces against microbes.
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Seema Rai, Bruce E Hirsch, Hubert H Attaway, Richard Nadan, S Fairey, J Hardy, G Miller, Donna Armellino, Wilton R Moran, Peter Sharpe, Adam Estelle, J H Michel, Harold T Michels and Michael G Schmidt
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M Souli, Z Chryssouli, I Galani, T Panayea, G Petrikkos, A Armaganidis, H Giamarellou (Chaidari, Athens, GR)
Copper has been shown to have antimicrobial properties and when
used on hospital surfaces it minimized environmental contamination
by pathogenic bacteria. We investigated the effects of two copper
alloys on the survival of VIM and/or KPC- producing multi-drug
resistant (MDR) Enterobacteriaceae.
View [PDF 51 kB]
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Peter A. Sharpe, MBA, EDAC, and Michael G. Schmidt, MA, PhD
Designing Clinical Trials To Evaluate New Materials and
Technologies
Summary
Hospitals clean environmental surfaces to lower microbial
contamination and reduce the likelihood of transmitting infections.
Despite current cleaning and hand hygiene protocols,
hospitalacquired infections (HAIs) continue to result in a
significant loss
of life and cost the U.S. healthcare system an estimated $45
billion annually. Stainless steel and chrome are often selected for
hospital touch surfaces for their "clean appearance," comparatively
smooth finish, resistance to standard cleaners, and relative
effectiveness for removing visible dirt during normal cleaning.
Designers use wood surfaces for aesthetics; plastic surfaces have
become increasingly endemic for their relative lower initial cost;
and "antimicrobial agents" are being incorporated into a variety of
surface finishes. This paper concentrates on environmental surface
materials with a history of bactericidal control of infectious
agents and focuses on the methods necessary to validate their
effectiveness in healthcare situations. Research shows copper-based
metals to have innate abilities to kill bacteria in laboratory
settings, but their effectiveness in patient care environments has
not been adequately investigated. This article presents a research
methodology to expand the evidence base from the laboratory to the
built environment. For such research to have a meaningful impact on
the design/specifying community, it should assess typical
levels of environmental pathogens (i.e., surface "cleanliness") as
measured by microbial burden (MB); evaluate the extent to which an
intervention with copper-based materials in a randomized clinical
trial affects the level of contamination; and correlate how the
levels of MB affect the incidence of infections acquired during
hospital stays.
Sharpe, P. A., & Schmidt, M. G. (2011). Control and
mitigation of healthcare-acquired infections: Designing clinical
trials to evaluate new materials and technologies. Health
Environments Research & Design Journal, 5(1), 94-115.
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Karpanen T J, Casey A L, Lambert P A, Cookson B D, Nightingale P, Miruszenko L and Elliott T S J. Infection Control and Hospital Epidemiology
Objective: To determine whether copper
incorporated into hospital ward furnishings and equipment can
reduce their surface microbial load.
Design: A crossover study.
Setting: Acute care medical ward with 19 beds
at a large university hospital.
Methods: Fourteen types of frequent-touch items
made of copper alloy were installed in various locations on an
acute care medical ward. These included door handles and push
plates, toilet seats and flush handles, grab rails, light switches
and pull cord toggles, sockets, overbed tables, dressing trolleys,
commodes, taps, and sink fittings. Their surfaces and those of
equivalent standard items on the same ward were sampled once weekly
for 24 weeks. The copper and standard items were switched over
after 12 weeks of sampling to reduce bias in usage patterns. The
total aerobic microbial counts and the presence of indicator
microorganisms were determined.
Results: Eight of the 14 copper item types had
microbial counts on their surfaces that were significantly lower
than counts on standard materials. The other 6 copper item types
had reduced microbial numbers on their surfaces, compared with
microbial counts on standard items, but the reduction did not reach
statistical significance. Indicator microorganisms were recovered
from both types of surfaces; however, significantly fewer copper
surfaces were contaminated with vancomycin-resistant enterococci,
methicillin-susceptible Staphylococcus aureus, and
coliforms, compared with standard surfaces.
Conclusions: Copper alloys (greater than or
equal to 58% copper), when incorporated into various hospital
furnishings and fittings, reduce the surface microorganisms. The
use of copper in combination with optimal infection-prevention
strategies may therefore further reduce the risk that patients will
acquire infection in healthcare environments.
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SL Warnes and CW Keevil, Applied and Environmental Microbiology, September 2011.
Contaminated touch surfaces have been implicated in the spread
of hospital-acquired infections, and the use of biocidal surfaces
could help to reduce this cross-contamination. In a previous study
we reported the death of aqueous inocula of pathogenic Enterococcus
faecalis or Enterococcus faecium isolates, simulating fomite
surface contamination, in 1 h on copper alloys, compared to
survival for months on stainless steel. In our current study we
observed an even faster kill of over a 6-log reduction of viable
enterococci in less than 10 min on copper alloys with a "dry"
inoculum equivalent to touch contamination. We investigated the
effect of copper(I) and copper(II) chelation and the quenching of
reactive oxygen species on cell viability assessed by culture and
their effects on genomic DNA, membrane potential, and respiration
in situ on metal surfaces. We propose that copper surface toxicity
for enterococci involves the direct or indirect action of released
copper ionic species and the generation of superoxide, resulting in
arrested respiration and DNA breakdown as the first stages of cell
death. The generation of hydroxyl radicals by the Fenton reaction
does not appear to be the dominant instrument of DNA damage. The
bacterial membrane potential is unaffected in the early stages of
wet and dry surface contact, suggesting that the membrane is not
compromised until after cell death. These results also highlight
the importance of correct surface cleaning protocols to perpetuate
copper ion release and prevent the chelation of ions by
contaminants, which could reduce the efficacy of the surface.
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Panos A Efstathiou, European Infectious Disease, 2011;5(2):125-8
Recent work investigating the antimicrobial characteristics of
copper has led to a re-evaluation of the role of this essential
metal in healthcare. While ancient civilisations used copper
for its health benefits it seems its usefulness has been
forgotten. The requirement for evidence-based interventions
for infection control has been the driver behind recent scientific
assessments of the benefits of copper. Ten years of
laboratory research has led to clinical trials confirming a very
significant and continuous reduction in environmental bioburden in
a number of healthcare settings globally. The newest and most
comprehensive clinical research has now reported an impressive 40%
reduction in healthcare-associated infections in intensive care
units (ICUs) where copper was incorporated in key touch
surfaces. The deployment of copper touch surfaces should be
considered as an additional infection control measure to reduce
care costs and improve bed availability and patient outcomes.
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W R Moran, H H Attaway, M G Schmidt, J F John, C D Salgado, K A Sepkowitz, R J Cantey, L L Steed, H T Michels. Poster presented at the American Hospital Association and Health Forum Leadership Summit 2011, July 17-19, 2011, San Diego, CA.
Each year hospital--‐acquired infections (HAI) result in a
substantial loss of life and an additional cost to the US
healthcare system of $45 billion dollars. Evidence is presented
illustrating how risk mitigation of the environmental burden
resulted in a concomitant mitigation of the HAI rates for patients
treated in rooms with antimicrobial copper touch surfaces. A
discussion of the complexities and costs associated with
effectively applying antimicrobial copper touch surfaces within the
built environment will facilitate an understanding of the need for
a design that makes use of emerging infection control solutions to
fight HAIs in a pragmatic and aesthetically satisfying way.
View [PDF 242 kB]
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Anton Shufutinsky, Harold Michels, Wilton Moran, Adam Estelle, James Michel, Chris Dreska, Dennis Simon.
Poster presented at 2011 US Armed Forces Public Health
Conference.
Summary:
Explains the potential application of Antimicrobial Copper
surfaces as a method for preventing surface and airborne microbial
contamination in military healthcare facilities, food handling
operations, and other occupational settings.
View [PDF 1323 kB]
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C Espírito Santo, E W Lam, C G Elowsky, D Quaranta, D W Domaille, C J Chang, and G Grass, 2011. Bacterial killing by dry metallic copper surfaces. Appl. Environ. Microbiol. 77: 794-802
Summary:
Metallic copper surfaces kill microbes on contact, decimating
their populations, according to a paper in the February 2011 issue
of the journal Applied and Environmental
Microbiology. They do so literally in minutes, by causing
massive membrane damage after about a minute's exposure, says the
study's corresponding author, Gregor Grass of the University of
Nebraska, Lincoln. This is the first study to demonstrate this
mechanism of bacteriocide.
"When microbes were exposed to copper surfaces, we observed
contact killing to take place at the rate of tens to hundreds of
millions of bacterial cells within minutes," says Grass. "This
means that usually no live microorganisms can be recovered from
copper surfaces after exposure."
Thus, such surfaces could provide a critical passive defense
against pathogens in hospitals, where hospital-acquired infections
are becoming increasingly common and costly, killing 50,000-100,000
Americans annually, and costing more than $8 billion, according to
one estimate. Still, Grass cautions that "metallic copper surfaces
will never be able to replace other hygiene-improving methods
already in effect," although they "will certainly decrease the
costs associated with hospital-acquired infections and curb human
disease as well as save lives." However, he expects this strategy
to be inexpensive, because "the effect does not wear off."
Critically, the researchers provide strong evidence that
genotoxicity through mutations and DNA lesions is not a cause of
dry copper's antimicrobial properties. This is important, because
mutations can cause cancer in animals and humans, and the lack of
such mutations in bacteria from copper means that copper does not
endanger humans.
The relevant experiment was particularly interesting. The
bacterium, Deinococcus radiodurans, is unusually
resistant to radiation damage, as its DNA repair mechanisms are
especially robust. The hypothesis: if metallic copper kills by
causing DNA damage, D. radiodurans should be immune
to copper. It is not.
It is important to note that only dry copper surfaces are
amazingly lethal to bacteria. The difference between dry and wet
surfaces, such as copper pipes, is that only dry surfaces are
inhospitable environments for bacterial growth. Bacteria can easily
grow and reproduce in wet environments, and in so doing, they can
develop resistance to copper. Resistance has not been observed to
develop on dry copper surfaces.
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Gregor Grass, Christopher Rensing and Marc Solioz, Appl. Environ. Microbiol. doi:10.1128/AEM.02766-10, American Society for Microbiology
Summary:
Bacteria, yeast, and viruses are rapidly killed on metallic
copper surfaces and the term 'contact-killing' has been coined for
this process. While the phenomenon has already been
known in ancient times, it is currently receiving renewed
attention. This is due to the potential use of copper as an
antibacterial material in health care settings. Contact-killing was
observed to take place at the rate of seven to eight logs per hour
or even minutes and no live microorganisms were generally recovered
from copper surfaces after prolonged incubation. The antimicrobial
activity of copper and copper alloys is now well established and
copper has recently been registered at the U.S. Environmental
Protection Agency as the first solid antimicrobial material. In
several clinical studies, copper has been evaluated for use on
touch-surfaces such as door handles, bathroom fixtures, or bed
rails, in attempts to curb nosocomial infections. In connection to
these new applications of copper, it becomes of importance to
understand the mechanism of contact-killing as it may bear on
central issues, such as the possibility of the emergence and spread
of resistant organisms, cleaning procedures, and questions of
material and object engineering. Recent work has shed light on
mechanistic aspects of contact-killing. These findings will be
reviewed here and juxtaposed to the toxicity mechanisms of ionic
copper. The merit of copper as a hygienic material in hospital and
related settings will also be discussed.
View [PDF 295 kB]
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Davide Quaranta, Travis Krans,
Christophe Espírito Santo, Christian G. Elowsky,
Dylan W. Domaille, Christopher J. Chang, and Gregor Grass, Applied and Environmental Microbiology. Jan. 2011, p. 416–426 Vol. 77, No. 2
0099-2240/11/$12.00 doi:10.1128/AEM.01704-10, American Society for Microbiology.
Summary:
Surfaces made of copper or its alloys have strong antimicrobial
properties against a wide variety of microorganisms. However,
the molecular mode of action responsible for the antimicrobial
efficacy of metallic copper is not known. Here, we show that
dry copper surfaces inactivate Candida albicans and
Saccharomyces cerevisiae within minutes in a process
called contact-mediated killing.
View [PDF 1305 kB]
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T J Karpanen, A L Casey, P A Lambert, B D Cookson, P Nightingale, L Miruszenko, T S J Elliott. 7th International Conference of the Hospital Infection Society, Liverpool, October 2010.
Summary
Results presented at the 7th International Conference of the
Hospital Infection Society in Liverpool, October 2010, confirm the
role of antimicrobial copper touch surfaces as a supplement to
routine cleaning to improve environmental hygiene in clinical
environments.
The results showed that the highest contamination was found in
the patient bathrooms, particularly on the chrome-plated toilet
flush lever handles and tap handles, and on the plastic light pulls
and toilet seats.
Copper-containing items, including door push plates, door pull
handles, tap handles, toilet flush lever handles, patient over-bed
tables, dressing trolleys, socket switches and light pull cord
toggles - were found to have significantly fewer microorganisms on
their surfaces than the controls and vancomycin-resistant
enterococci, meticillin-sensitive Staphylococcus aureus
and coliform bacteria were recovered less frequently from
these.
View [PDF 476 kB]
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B E Hirsch, H Attaway, R Nadan, S Fairey, J Hardy, G Miller, S Rai, D Armellino, M Schilling, W Moran, P Sharpe, A Estelle, J H Michel, H T Michels, M G Schmidt - presented in a poster session at the Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC) in Boston, MA, September 13 2010.
Summary
Copper alloy surfaces are known to kill bacteria and decrease
the environmental microbial bio-burden (MB) in ICUs. Out-patients
share risk factors including co-morbidities, antibiotic exposure
plus recent hospitalisation. The transient and high volume of
potentially infectious and vulnerable subjects renders the
out-patient clinic a significant locus of transmission that is
often overlooked. This study shows the benefit of copper surfaces
for their ability to reduce the MB in an infectious disease
out-patient practice. These findings support
the clinical trial findings from Selly Oak, Calama
and MUSC and, in addition, show a halo effect - reduced
contamination in the vicinity of the copper surfaces. The
calculated ratio of patients to the median burden enabled the
conclusion to be drawn that use of the chair with the copper arm
tops resulted in a 17-fold lower risk of exposure to environmental
microbes than when patients used the standard chair.
View [PDF 98 kB]
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S L Warnes, S M Green, H T Michels, C W Keevil, Appl. Environ. Microbiol. doi:10.1128/AEM.03050-09, 2010
Summary:
The increasing incidence of nosocomial infections caused by
glycopeptide-resistant enterococci is a global concern.
Enterococcal species are also difficult to eradicate with existing
cleaning regimes; they can survive for long periods on surfaces
thus contributing to cases of reinfection and spread of antibiotic
resistant strains. We have investigated the potential use of copper
alloys as bactericidal surfaces. Clinical isolates of
vancomycin-resistant Enterococcus faecalis and Enterococcus faecium
were inoculated onto copper alloy and stainless steel surfaces.
Samples were assessed for the presence of viable cells by
conventional culture, detection of actively respiring cells and
assessment of cell membrane integrity. Both species survived for up
to several weeks on stainless steel. However, no viable cells were
detected on any alloys following exposure for 1 hour at an inoculum
concentration of ≤104 colony forming units per
cm2. Analysis of genomic and plasmid DNA from bacterial
cells recovered from metal surfaces indicates substantial
disintegration of the DNA following exposure to copper surfaces
that is not evident in cells recovered from stainless steel. The
DNA fragmentation is so extensive, and coupled with the rapid cell
death which occurs on copper surfaces, that it suggests mutation is
less likely to occur. It is therefore highly unlikely that genetic
information can be transferred to receptive organisms
re-contaminating the same area. A combination of effective cleaning
regimes and contact surfaces containing copper could be useful to
not only prevent spread of viable pathogenic enterococci but also
to mitigate against the occurrence of potential resistance to
copper, biocides or antibiotics, and spread of genetic determinants
of resistance to other species.
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C D Salgado, A Morgan, K A Sepkowitz et al. Poster 183, 5th Decennial International Conference on Healthcare-Associated Infections, Atlanta, March 29, 2010
Summary:
The first results from the US Department of Defense-funded
3-centre copper clinical trial show a significant reduction in
bioburden on copper items compared to controls. Neither VRE nor
MRSA were found on any copper items.
View [PDF 272 kB]
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H T Michels, J O Noyce, and C W Keevil, Letters in Applied Microbiology, 49 (2009) 191-195
Summary:
Demonstrates that commercially available silver ion-containing
coatings marketed as antimicrobial do not exhibit any meaningful
reduction of MRSA under typical indoor conditions. Copper alloys
exhibited antimicrobial efficacy under all tested conditions.
View [PDF 136 kB]
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V Prado, C Durán, M Crestto, A Gutierrez, P Sapiain, G Flores, H Fabres, C Tardito, M Schmidt. Poster 56.044, presented at the 14th International Conference on Infectious Diseases, Miami, March 11, 2010.
Summary
First results from the Calama Hospital copper clinical trial
show a significant reduction in bioburden on copper compared to
control surfaces.
View [PDF 342 kB]
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André Mikolay, Susanne Huggett, Ladji Tikana, Gregor Grass, Jörg Braun and Dietrich H Nies. Applied Microbial and Cell Physiology,
DOI 10.1007/s00253-010-2640-1. May 2010
Summary:
Basic chemistry of copper is responsible for its Janus-faced
feature: on one hand, copper is an essential trace element required
to interact efficiently with molecular oxygen. On the other hand,
interaction with reactive oxygen species in undesired Fenton-like
reactions leads to the production of hydroxyl radicals, which
rapidly damage cellular macromolecules. Moreover, copper cations
strongly bind to thiol compounds disturbing redox-homeostasis and
may also remove cations of other transition metals from their
native binding sites in enzymes. Nature has learned during
evolution to deal with the dangerous yet important copper cations.
Bacterial cells use different efflux systems to detoxify the metal
from the cytoplasm or periplasm. Despite this ability, bacteria are
rapidly killed on dry metallic copper surfaces. The mode of killing
likely involves copper cations being released from the metallic
copper and reactive oxygen species. With all this knowledge about
the interaction of copper and its cations with cellular
macromolecules in mind, experiments were moved to the next level,
and the antimicrobial properties of copper-containing alloys in an
"everyday" hospital setting were investigated. The alloys tested
decreased the number of colony-forming units on metallic
copper-containing surfaces by one third compared to control
aluminum or plastic surfaces. Moreover, after disinfection,
repopulation of the surfaces was delayed on copper alloys. This
study bridges a gap between basic research concerning cellular
copper homeostasis and application of this knowledge. It
demonstrates that the use of copper-containing alloys may limit the
spread of multiple drug-resistant bacteria in hospitals.
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D Hamilton, A Foster, L Ballantyne, P Kingsmore, D Bedwell, T J Hall, S S Hickok, A Jeanes, P G Coen, V A Gant, Journal of Hospital Infection (2010) 74, 62-71. doi:10.1016/j.jhin.2009.08.006.
Summary
This study compared the bacterial removal performance of
ultromicrofibre cloths and mops (UMF) moistened with water (UMF +
water) with those moistened with a novel copper-based biocide (UMF
+ CuWB50, 300 ppm) in several working hospital environments,
specifically Accident and Emergency (A&E) and three other
wards.
A total of 13 defined sampling sites (10 sites per ward) were
sampled in order to retrieve, culture, and enumerate total viable
(bacterial) counts (TVC) for each site. We sampled 1h before,
and 1 and 4h after, cleaning three times per week. The trial
ran for 7 weeks. Two wards were cleaned with UMF + water for
3 weeks and UMF + CuWB50 for 4 weeks. The reverse applied to
the other two wards in a cross-over design fashion, to eliminate
ward- and time-specific bias. Multivariate statistical
analyses were used to establish extent and significance of any
perceived differences, and to eliminate the effects of potential
confounders. Cleaning with UMF + water reduced TVC on the
test surfaces by 30%, whereas cleaning with TVC + CuWB50 reduced
TVC by 56%. CuWB50 had two separate effects; a direct
antibacterial effect (evident shortly after cleaning), and a
residual antibacterial effect that lasted approx 2 weeks. The
residual effect requires regular application of CuWB50 if it is to
persist. This 'real life' hospital implementation study
demonstrates encouraging microbiological cleaning performance for
UMF, which is further enhanced with CuWB50.
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A L Casey, D Adams, T J Karpanen, P A Lambert, B D Cookson, P Nightingale, L Miruszenko, R Shillam, P Christian and T S J Elliott, J Hosp Infect (2009), doi:10.1016/j.jhin.2009.08.018.
Summary
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 cm2 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 <5 cfu/cm2. 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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L Weaver, H T Michels, C W Keevil, Letters in Applied Microbiology ISSN 0266-8254 (2010) 50 (1): 18. doi:10.1111/j.1472-765X.2009.02753.x. PMID 19943884.
Aims:
As copper has been previously suggested as an antimicrobial
surface, the effectiveness of copper was investigated as an
antifungal surface which could be used in air-conditioning systems
as an alternative to aluminium.
Methods and Results:
Coupons of copper (C11000) and aluminium were inoculated with
fungal isolates (Aspergillus spp., Fusarium spp., Penicillium
chrysogenum and Candida albicans) for various time periods. Culture
on potato dextrose agar and an in situ viability assay using the
fluorochrome FUN-1 were used to determine whether spores had
survived. The results showed increased
die off of fungal isolates tested compared to aluminium. In
addition, copper also prevented the germination of spores present,
thereby reducing the risk of the release of spores.
Conclusions:
Copper offered an antifungal surface and prevented subsequent
germination of spores present. FUN-1 demonstrated that fungal
spores entered into a viable but not culturable (VBNC) state on
copper indicating the importance of using such methods when
assessing the effect of an antifungal as culture alone may give
false results.
Significance and impact of study:
Copper offers a valuable alternative to aluminium which could
be used in air-conditioning systems in buildings, particularly in
hospital environments where patients are more susceptible to fungal
infections.
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Marais F et al, J Hosp Infect (2009), doi:10.1016/j.jhin.2009.07.010.
Summary
A comparative controlled study was conducted at a busy walk-in
primary healthcare clinic (PHC) in Grabouw, a rural region of the
Western Cape, South Africa, to demonstrate antimicrobial efficacy
of copper touch surfaces in reducing bioburden in a community
healthcare facility.
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Kristopher Page, Michael Wilson and Ivan P Parkin, University College London. January 2009. J. Mater. Chem. 2009 DOI: 10.1039/b818698g
Summary:
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.
View [PDF 236 kB]
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S W J Gould, M D Fielder, A F Kelly, M Morgan, J Kenny, D P Naughton,
Annals of Microbiology, 59 (1) 151-156 (2009)
Summary
Hospital-acquired infections (HAI) are a major problem worldwide
and controlling the spread of these infections within a hospital is
a constant challenge. Recent studies have highlighted the
antimicrobial properties of copper and its alloys against a range
of different bacteria.
The objective of this study was to evaluate the antimicrobial
properties of copper compared to stainless steel against a range of
clinically important pathogens. These pathogens consisted of
five isolates of each of the following organisms; meticillin
resistant Staphylococcus aureus (MRSA), Pseudomonas
aeruginosa, Escherichia coli, vancomycin-resistant
Enterococci (VRE) and Panton-Valentine Leukocidin positive
community acquired-MSSA (PVL positive CA-MSSA, MRSA, P.
aeruginosa, E.coli and CA-MSSA isolates were not
detectable after a median time of 60 minutes. No detectable
levels for all VRE iosolates were determined after a median time of
40 minutes. However, for all isolates tested the stainless
steel had no effect on the survival of the bacteria and levels
remained similar to the time zero count.
The results of this study demonstrate that copper has a strong
antimicrobial effect against a range of clinically important
pathogens compared to stainless steel and potentially could be
employed to aid the control HAI.
View [PDF 398 kB]
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C D Salgado, K A Sepkowitz, T Plaskett, J F John, J R Cantey, H H Attaway, L L Steed, H T Michels, M G Schmidt. October 2008.
Summary:
This study sought to determine the microbial burden (MB) on
frequently touched inanimate objects in the ICU rooms of patients
at three different US hospitals.The findings showed that
Staphylococci were the predominant organism isolated within this
MB.
Objects found in ICU rooms can serve as a reservoir for the
spread of bacteria, particularly staphylococci, to patients,
healthcare workers, and visitors. Objects in close proximity
to patients pose the greatest risk, particulalry bed rails.
Patient acquisition of organisms that were recovered from ICU
rooms may lead to healthcare-acquired infections resulting in
substantial morbidity and mortality. Future studies should
focus on strategies to reduce high level bacterial contamination of
common objects in patient rooms and potential spread of these
bacteria in order to potentially reduce healthcare-acquired
infections.
View [PDF 54 kB]
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A L Casey, P A Lambert, L Miruszenko, T S J Elliott. October 2008
Poster presented at the Interscience Conference on Antimicrobial
Agents and Chemotherapy (ICAAC), October 2008.
View [PDF 1240 kB]
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H Michels, W Moran and J Michel, International Journal of Metalcasting, Summer 2008, pp 47-56
Summary:
Discusses the antimicrobial properties of copper alloys and
their potential to reduce the amount of certain bacteria on
frequently touched surfaces. Efficacy data address other materials
and the effects of tarnishing, bacteria concentration and repeated
contamination. EPA testing, results and registration are
highlighted.
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L. J. Wheeldon, T. Worthington, P. A. Lambert, A. C. Hilton, C. J. Lowden and T. S. J. Elliott, Journal of Antimicrobial Chemotherapy 2008 62(3):522-525; doi:10.1093/jac/dkn219.
Summary
Methods: 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 3h period in the presence and absence of
organic matter.
Results: 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 
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).
Conclusions: 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.
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H T Michels and D G Anderson, pp 185-190, Metal Ions in Biology and Medicine: Vol 10, Eds Ph Collery, I Maymard, T Theophanides, L Khassanova, T Collery. John Libbey Eurotext, Paris © 2008
Summary:
Discusses potential impact of antimicrobial copper alloys on
amount of certain bacteria on frequently touched surfaces in
healthcare settings. Describes the steps required to make
public health claims and summarises EPA test protocols and
results.
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L Weaver, H T Michels, and C W Keevil, Journal of Hospital Infection, Vol 68, Issue 2, pp 145-151, February 2008
Summary:
Compares the viability of Clostridium difficile on
copper and stainless steel. Reports a significant reduction of
Clostridium difficile was observed on alloys with >70%
copper content while no reduction is observed on steel. Suggests
use of copper alloys in hospitals may reduce the levels of
Clostridium difficile on frequently touched surfaces.
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S Mehtar, I Wiid, and S D Todorov
Journal of Hospital Infection, Vol. 68, Issue 1, pp 45-51, January 2008
Summary:
Compares the viability of MRSA, Klebsiella pneumonia,
Pseudomonas aeruginosa, Acinetobacter baumannii,
Candida albicans and Mycobacterium tuberculosis on copper
alloys, stainless steel and PVC. Results illustrate copper's
ability to kill pathogens most commonly associated with
hospital-acquired infections. No effect was observed on PVC
and stainless steel.
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J O Noyce, H Michels and C W Keevil, Applied and Environmental Microbiology, pp 2748 - 2750, Vol 73, No 8, April 2007
Summary:
Uses fluorescent microscopy to compare viability of Influenza A
on copper and stainless steel. Copper showed a 4-log reduction
after 6 hours while steel only showed a 1-log reduction after 24
hours.
View [PDF 445 kB]
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H T Michels, D G Anderson, J O Noyce, S A Wilks and C W Keevil, Proceedings of the Sixth International Copper-Cobre Conference, pp 121-133, Vol I, August 2007
Summary:
Describes potential healthcare applications and barriers for
antimicrobial copper alloys. Authors review efficacy data against
various organisms and EPA testing.
View [PDF 723 kB]
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S A Wilks, H T Michels and C W Keevil, International Journal of Food Microbiology, 111, September (2006), pp 93-98.
Summary:
Compares the viability of Listeria monocytogenes on
various copper alloys and stainless steel. Copper-based alloys
produced a significant reduction in viability compared to stainless
steel. Suggests materials selection could impact bioload in various
environments.
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H T Michels, ASTM Standardization News, October 2006.
Summary:
Article provides an overview on the antimicrobial characteristic
of copper. Describes the research performed to date and the
potential applications of antimicrobial copper products. Includes a
letter from the editor which highlights the article.
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J O Noyce, H Michels and C W Keevil, Journal of Hospital Infection, Vol 63, Issue 3, pp 289-297, July 2006
Summary:
Demonstrates copper's ability to kill epidemic
Methicillin-resistant Staphylococcus aureus under
different conditions in comparison to stainless steel. Illustrates
effects of bacteria concentration, temperature and copper content
on antimicrobial efficacy.
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J O Noyce, H Michels, and C W Keevil, Applied and Environmental Microbiology, pp 4239-4244, June 2006.
Summary:
Investigates ability of copper to kill Escherichia coli
O157:H7 which is responsible for diseases caused by food
contamination. Incorporates beef juice with bacteria to simulate
food cross contamination scenario. High copper containing alloys
greatly reduced the amount of E. coli O157:H7 at room
(22C) and low temperatures (4C). Stainless steel, the control, had
no effect.
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S A Wilks, H Michels and C W Keevil, International Journal of Food Microbiology, 105 (2005), pp 445-454.
Summary:
Compares the survivability of an infectious strain of
Escherichia coli on copper alloys and stainless steel.
Copper alloys exhibited a large reduction within several hours
while stainless steel did not. Addresses the advantages of
alloying and suggests using antimicrobial surfaces in environments
where bacterial contamination is a concern.
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H T Michels, J P Noyce, S A Wilks and C W Keevil. Copper for the 21st Century, Materials Science & Technology 2005 (MS&T’05) Conference, Pittsburgh, PA, September 25-28, 2005, ASM, ACerS, AIST, AWS, TMS, ISSN: 1546-2498
Summary:
Illustrates the ability of copper alloys to kill several food
borne pathogens known to cause infection. Also demonstrates
efficacy against Methicillin-resistant Staphylococcus
aureus which is largely responsible for hospital acquired
infections. Stainless steel, the control, had no effect on any of
the pathogens. Results suggest copper alloys may reduce the levels
of infectious pathogens on surfaces in contact with food and
touched by humans.
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P Tandon, S Chhibber and R Reed, Antonie van Leeuwenhoek (2005) 88:35-4, 14pp
Summary:
The detection and enumeration of indicator bacteria such as
Escherichia coli is used to assess the extent of faecal
contamination of drinking water. On the basis of this approach, the
effectiveness of storing water contaminated with faecal indicator
bacteria in brass or earthen vessels (mutkas) of the type used in
rural India have been investigated.
Suspensions of bacteria in sterile distilled water were
maintained for up to 48 h in each vessel and enumerated by
surface plate counts on nutrient agar (non-selective) and several
selective coliform media at 37 °C either under standard
aerobic conditions, or under conditions designed to neutralise
reactive oxygen species (ROS), e.g. using an anaerobic cabinet to
prepare plates of pre-reduced growth medium or by inclusion of
sodium pyruvate in the growth medium, with incubation of
aerobically-prepared plates in an anaerobic jar.
The counts obtained for E. coli decreased on short-term
storage in a brass mutka; counts for selective media were lower
than for equivalent counts for non-selective medium, with
ROS-neutralised conditions giving consistently higher counts than
aerobic incubation. However, after 48 h, no bacteria were
cultivable under any conditions. Similar results were obtained
using water from environmental sources in the Panjab, and from
rural households where brass and earthern mutkas are used for
storage of drinking water, with enumeration on selective coliform
media (presumptive total coliforms). In all cases results indicated
that, while storage of water in a brass mutka can inactivate E.
coli and coliforms over a 48 h period, standard aerobic
plate counting using selective media may not be fully effective in
enumerating sub-lethally damaged bacteria.
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H T Michels. Plumbing Standards - An Official Publication of the American Society of Sanitary Engineers, October-December, 2004
Summary:
Reviews numerous studies and papers that illustrate copper's
ability to kill a variety of organisms known to cause infection.
Emphasis is placed on Legionella pneumophila which is
transferred through piping systems (i.e. HVAC, water delivery) and
has caused a number of pneumonia outbreaks. Results suggest
copper can reduce the levels of harmful pathogens in plumbing
networks.
View [PDF 3945 kB]
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H T Michels, S A Wilks and C W Keevil. The Second Global Congress Dedicated to Hygienic Coatings & Surfaces, Orlando, Florida, USA, 26-28 January, 2004, Paper 16, Published by Paint Research Association, Middlesex, UK, ISBN 0-9543164-5-2, 2004.
Summary:
Tests the viability of E. coli O157:H7 on a variety of
copper alloy surfaces. All tested copper alloys rendered the
bacteria non viable after several hours. E. coli O157:H7 has been
responsible for a number of food recalls and can survive on
stainless steel for days. Results suggest copper alloys will be
useful beyond food processing applications.
View [PDF 747 kB]
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H T Michels, S A Wilks and C W Keevil, Proceedings of Copper 2003 - Cobre 2003, The 5th International Conference, November 30-December 2, 2003, Santiago, Chile, Vol. 1 - Plenary Lectures, Economics and Applications of Copper, pp. 439-450, A Publication of The Canadian Institute of Mining, Metallurgy and Petroleum, Montreal, Quebec, Canada, 2003
Summary:
Investigates the viability of E. coli O157:H7 on 25
copper alloy surfaces at 20C and 4C (refrigeration
temperature). Bacteria reduction occurred with all alloys and
was faster at the higher temperature and on alloys containing
higher levels of copper. Further research is recommended to
determine copper's effect on moulds and other organisms that cause
respiratory infections.
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P J Kuhn, Diagnostic Medicine, 1983.
Summary:
Discusses the unique bactericidal properties of copper and brass
compared to stainless steel and aluminum against various
organisms. Results suggest that hospitals should utilise
brass (copper alloy) hardware to minimise bacterial growth on these
surfaces.
View [PDF 424 kB]