We need an appropriate antimicrobial test standard for indoor touch surfaces

Concerned by HCAIs (infections acquired during healthcare) and Antimicrobial Resistance?

Here’s something you should know…

Use of effective antimicrobial surfaces, as a simple supplement to good hand hygiene and cleaning regimes, has been proven to reduce not only microbial bioburden on frequently-touched surfaces but also patient infection rates.

In healthcare, fewer infections mean better healthcare efficiency (clinical cost-savings and freed-up beds) and improved patient outcomes.

Thus far, no major surprises… but what about this?
Not all antimicrobials are equal and there is no universally-adopted standard test protocol to measure their effectiveness ‘in the field.’

How, then, can we identify and specify appropriate antimicrobial surfaces to use in construction or refurbishment projects?

Healthcare scientists and clinicians urge careful stewardship of antimicrobial agents; this includes antimicrobial surfaces as well as antibiotic drugs.

Some commonly-used antimicrobial surfaces – which work under the standard “warm and wet” test protocols* – have negligible efficacy under typical indoor conditions.**

Using such surfaces could actually aggravate the problem of antimicrobial resistance, which the WHO described in April 2015 as “the single greatest challenge in infectious disease today.”

There are appropriate tests currently available in the UK which are ready to be used.***

Until we agree an appropriate test standard for antimicrobial efficacy – relevant to touch surfaces under typical indoor conditions – needless suffering will continue and we will deny ourselves a simple yet effective measure that improves healthcare and helps combat antimicrobial resistance.

Regulators such as the US EPA and the OECD are aware of this. The OECD Working Group under the Inter-Organisation Programme for the Sound Management of Chemicals (IOMC), which represents the interests of a number of countries and regions, has proposed a tiered system approach with Tier One test methods providing proof of principle and Tier Two methods more closely representing in-use environmental conditions.

For a more comprehensive explanation, with details of efficacy tests performed on Antimicrobial Copper,  visit: http://www.antimicrobialcopper.org/uk/efficacy-tests-and-standards


So, the next time a salesman or colleague talks to you about an antimicrobial surface, ask:-
a) is it able to make public health benefit claims?
b) does it work rapidly, under typical indoor conditions?
c) how does it work – does it actually destroy microbes?
d) how durable is the antimicrobial protection?
e) is use of this product likely to contribute to AMR?
f) for evidence – not claims, but test protocols and results over time
and, last but not least:

g) help raise awareness of the need for an appropriate test standard for antimicrobial efficacy under typical indoor conditions!


We welcome your suggestions: please contact us.



* JIS Z 2801 or ISO 22196 (measure microbial reduction at 24 hours exposure, under elevated temperature and saturated humidity conditions).

** Michels, H.T., Noyce, J.O. and Keevil, C.W. (2009), Effects of temperature and humidity on the efficacy of methicillin-resistant Staphylococcus aureus challenged antimicrobial materials containing silver and copper. Letters in Applied Microbiology, 49: 191–195. doi: 10.1111/j.1472-765X.2009.02637.x

*** OECD is aware of the limitations of standard tests, which OECD class as Tier 1 tests.
The available tests referred to in this post constitute Tier 2 tests as per para 2 on page 8 of OECD  “GUIDANCE DOCUMENT FOR QUANTITATIVE METHOD FOR EVALUATING ANTIBACTERIAL ACTIVITY OF POROUS AND NON-POROUS ANTIBACTERIAL TREATED MATERIALS”  ENV/JM/MONO(2014)18 dated 11th July 2014
“2. The method provides only a basic foundation for conducting tests on antimicrobial treated articles, and a second tier method must be developed to ensure an accurate assessment of antimicrobial activity. A guidance document is currently under development for tier 2 testing, i.e. laboratory-based tests to substantiate claims made for the article with test conditions that simulate intended use, durability and compatibility of the article – provided that the protocol describes the claim being supported in an adequate manner. Further, Tier 2 testing protocols will also accommodate use of shorter contact times (e.g. 2h) and inoculum dried on treated surfaces.”
See http://www.oecd.org/officialdocuments/publicdisplaydocumentpdf/?cote=ENV/JM/MONO(2014)18&doclanguage=en

Recent Publications & Papers

Interest in (and research into) the real-world efficacy and kill mechanisms of metallic copper surfaces against microbes (bacteria, viruses, yeasts and fungi) is accumulating.

Here are some recent papers for you:


Michels HT, Keevil CW, Salgado CD, Schmidt MG. 2015. From Laboratory Research to a Clinical Trial: Copper Alloy Surfaces Kill Bacteria and Reduce Hospital-Acquired Infections HERD, October 2015 vol. 9 no. 1 64-79,

This paper, published in HERD, helps summarise and explain the mechanisms, efficacy and benefits of copper & copper-alloy touch surfaces (collectively called “Antimicrobial Copper”).
It is open-access, so you can download the full pdf without cost.


Warnes SL, Little ZR, Keevil CW. 2015. Human coronavirus 229E remains infectious on common touch surface materials. mBio 6(6):e01697-15. doi:10.1128/mBio.01697-15.

Animal coronaviruses that ‘host jump’ to humans, such as SARS and MERS, result in severe infections with high mortality. The Southampton researchers found that a closely-related human coronavirus – 229E – can remain infectious on common surface materials for several days, but is rapidly destroyed on copper.


Hans M, Mathews S, Mücklich F, Solioz M. 2015. Physicochemical properties of copper important for its antibacterial activity and development of a unified model. Biointerphases 11, 018902 (2016); doi: 10.1116/1.4935853

Abstract: Contact killing is a novel term describing the killing of bacteria when they come in contact with metallic copper or copper-containing alloys. In recent years, the mechanism of contact killing has received much attention and many mechanistic details are available.
The authors here review some of these mechanistic aspects with a focus on the critical physicochemical properties of copper which make it antibacterial. Known mechanisms of contact killing are set in context to ionic, corrosive, and physical properties of copper.
The analysis reveals that the oxidation behavior of copper, paired with the solubility properties of copper oxides, are the key factors which make metallic copper antibacterial. The concept advanced here explains the unique position of copper as an antibacterial metal. Based on our model, novel design criteria for metallic antibacterial materials may be derived.

Meyer, T.J. 2015. Antimicrobial Properties of Copper in Gram-Negative and Gram-Positive Bacteria. International Journal of Biological, Biomolecular, Agricultural, Food and Biotechnological Engineering. Vol:9, No:3.

Abstract: For centuries humans have used the antimicrobial properties of copper to their advantage. Yet, after all these years the underlying mechanisms of copper mediated cell death in various microbes remain unclear. We had explored the hypothesis that copper mediated increased levels of lipid peroxidation in the membrane fatty acids is responsible for increased killing in Escherichia coli.
In this study we show that in both gram positive (Staphylococcus aureus) and gram negative (Pseudomonas aeruginosa) bacteria there is a strong correlation between copper mediated cell death and increased levels of lipid peroxidation.
Interestingly, the non-spore forming gram positive bacteria as well as gram negative bacteria show similar patterns of cell death, increased levels of lipid peroxidation, as well as genomic DNA degradation, however there is some difference in loss in membrane integrity upon exposure to copper alloy surface.


These papers are also recommended:


Taylor M, Chaplin S. 2013. The Economic Assessment of an Environmental Intervention: Discrete Deployment of Copper for Infection Control in ICUs. Antimicrobial Resistance and Infection Control 2013, 2(Suppl1):P368

This paper is the York Health Economics Consortium research into the cost-effectiveness and payback of copper touch surfaces. Read more, with a worked example for a UK 20 bed ICU, in this pdf document YHEC Business Case (CDA Pub 212)

More information on CDA website antimicrobialcopper.org http://www.antimicrobialcopper.org/uk/the-business-case


Warnes SL, Keevil CW. 2011. Mechanism of copper surface toxicity in Vancomycin-resistant enterococci following wet or dry surface contact. Applied and Environmental Microbiology, Sept. 2011. pp. 6049–6059.

Abstract: 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.

Warnes, S.L. et al. 2012.  Horizontal transfer of antibiotic resistance genes on abiotic touch surfaces: implications for public health.  MBio 2012 Nov; 3(6):e00489-12. DOI:10.1128/mBio.00489-12.

“This study demonstrated that HGT readily occurs on dry touch surfaces such as stainless steel, providing a potentially important route for multidrug resistance emergence and dissemination in public buildings and transportation systems if surfaces are not regularly and efficiently cleaned…. The use of copper alloys in clinical and community settings could help reduce infection spread and also reduce the incidence of horizontal transmission genes conferring drug resistance, virulence, and pathogenesis and expression efficiency.”

Further references:

CDA publication 196 “Reducing the Risk of HCAIs” outlines the research and key results; it also contains a useful structured bibliography of references. You can download it here: http://www.antimicrobialcopper.org/sites/default/files/upload/Media-library/Files/PDFs/UK/Brochures/pub-196-reducing-risk-healthcare-infections.pdf

Further scientific references are available on CDA website antimicrobialcopper.org at  http://www.antimicrobialcopper.org/uk/scientific-references