A recent microbe.net post discussed the use of copper as an antimicrobial to prevent infections in healthcare settings. This is not a particularly new concept, but unfortunately, the literature appears dominated by authors who received funding from the copper industry and its associations. Such industrial funding is not unique to copper and is, sadly, more widespread than might be generally recognized or appreciated.
Our downloadable database of more than 360 published articles on the indoor environment and the indoor microbiome includes a couple of papers that also address the subject of copper as an antimicrobial. In both cases, the authors acknowledge at least a portion of their funding from copper industry sources (although they also acknowledged some funding from NIH).
The question about the antimicrobial efficacy of copper is a good one, and research into its efficacy as a biocide is important. Obviously there has been a lot of such research, and a responsible review of the literature would be welcome. Copper can be combined with other metals for doorknobs, handles on faucets and toilets, and other high contact surfaces both in healthcare facilities and beyond. The high market value of copper means that the vast majority of it is not land-filled or otherwise discarded at the end of its service life, but is recycled and re-used, thus minimizing the depletion of the natural resource and reducing the life-cycle environmental impacts associated with its mining, production, and use.
Like Eisen and Miller, who expressed skepticism in comments on the article that was the subject of the recent post (or was their skepticism on the content of the blog post itself?), I find the paper’s authors’ association with the copper industry troubling. But I can’t help wondering if there is any merit to the article at all or to the idea that copper might be at least somewhat effective even if it is not the “magic bullet.”
The funding and the authors’ affiliation casts suspicion on the article’s conclusions, and raises questions as to how their paper (or the microbe.net blog post on it) got published. The paper contains no description of the methodology used to conduct the literature review, no criteria for inclusion or exclusion of papers, or other criteria for determination of credibility. It would be useful if someone identified the weaknesses in the authors’ process and findings, and conducted a search for evidence that undermines or contradict the article’s findings.
Among the our database’s more than 360 published articles on the indoor environment and the indoor microbiome, are a couple of papers that also address the subject of copper as an antimicrobial. In both cases, the authors acknowledge at least a portion of their funding from copper industry sources although they also received some funding from NIH. Both papers find copper useful as an antimicrobial.
One of the papers included in our database is a minireview published in Applied and Environmental Microbiology, [Grass, Gregor, Christopher Rensing, and Marc Solioz,2011. Metallic Copper as an Antimicrobial Surface. Applied and Environmental Microbiology Mar. 2011, p. 1541-1547]. Note that these authors also received support from the copper industry along with support from the Swiss National Foundation and NIH. The paper includes some hospital trials that make the paper worth reading. It is summarized as follows in the abstract:
Bacteria, yeasts, and viruses are rapidly killed on metallic copper surfaces, and the term “contact killing” has been coined for this process. While the phenomenon was already known in ancient times, it is currently receiving renewed attention. This is due to the potential use of copper as an antibacterial material in health care settings. Contact killing was observed to take place at a rate of at least 7 to 8 logs per hour, and no live microorganisms were generally recovered from copper surfaces after prolonged incubation. The antimicrobial activity of copper and copper alloys is now well established, and copper has recently been registered at the U.S. Environmental Protection Agency as the first solid antimicrobial material. In several clinical studies, copper has been evaluated for use on touch surfaces, such as door handles, bathroom fixtures, or bed rails, in attempts to curb nosocomial infections. In connection to these new applications of copper, it is important to understand the mechanism of contact killing since it may bear on central issues, such as the possibility of the emergence and spread of resistant organisms, cleaning procedures, and questions of material and object engineering. Recent work has shed light on mechanistic aspects of contact killing. These findings will be reviewed here and juxtaposed with the toxicity mechanisms of ionic copper. The merit of copper as a hygienic material in hospitals and related settings will also be discussed.
[Grass, Gregor, Christopher Rensing, and Marc Solioz,2011. Metallic Copper as an Antimicrobial Surface. Applied and Environmental Microbiology Mar. 2011, p. 1541-1547].
The conclusion begins as follows:
“The antimicrobial properties of copper surfaces have now been firmly established. Hospital trials have shown a reduction in bacterial counts, indicating that copper surfaces are a promising additional tool alongside other hygienic measures to curb the number and severity of hospital-acquired infections.”
Another paper in our database, Elguindi, Jutta, Xiuli Hao, Yanbing Lin, Hend A. Alwathnani, Gehong Wei and Christopher Rensing, 2011. Advantages and challenges of increased antimicrobial copper use and copper mining. Appl Microbiol Biotechnol (2011) 91:237-249. The authors acknowledge funding from various sources including “ICA.” (Could this be the International Copper Association?) This paper is also a “mini-review,” summarized in its abstract as follows:
“Copper is a highly utilized metal for electrical, automotive, household objects, and more recently as an effective antimicrobial surface. Copper-containing solutions applied to fruits and vegetables can prevent bacterial and fungal infections. Bacteria, such as Salmonellae and Cronobacter sakazakii, often found in food contamination, are rapidly killed on contact with copper alloys. The antimicrobial effectiveness of copper alloys in the healthcare environment against bacteria causing hospital-acquired infections such as methicillin-resistant Staphylococcus aureus (MRSA), Escherichia coli O157:H7, and Clostridium difficile has been described recently. The use of copper and copper-containing materials will continue to expand and may lead to an increase in copper mining and production. However, the copper mining and manufacturing industry and the consumer do not necessarily enjoy a favorable relationship. Open pit mining, copper mine tailings, leaching products, and deposits of toxic metals in the environment often raises concerns and sometimes public outrage. In addition, consumers may fear that copper alloys utilized as antimicrobial surfaces in food production will lead to copper toxicity in humans. Therefore, there is a need tomitigate some of the negative effects of increased copper use and copper mining. More thermo-tolerant, copper ion-resistant microorganisms could improve copper leaching and lessen copper groundwater contamination. Copper ion-resistant bacteria associated with plants might be useful in biostabilization and phytoremediation of copper-contaminated environments. In this review, recent progress in microbiological and biotechnological aspects of microorganisms in contact with copper will be presented and discussed, exploring their role in the improvement for the industries involved as well as providing better environmental outcomes.”
So what is known that precludes use of copper for its antimicrobial properties and its potential usefulness to help control spread of infection through contact surfaces? Even if not the panacea described in the blog post, could copper be helpful?
Our database is freely downloadable here).