Copper kills superbugs, wet or dry...

Superbugs last days on doorhandles. But if we made them from copper they could kill microbes in seconds. How does the metal do it?
26 February 2016

Interview with 

Professor Bill Keevil, University of Southampton


Florence Nightingale's design for hospital wards is largely out of favour these A hospital beddays, but the interior decor of a century ago - including the brass door handles - might be about to make a comeback. Not so much on aesthetic grounds but because, as Southampton scientist Bill Keevil has discovered, copper-rich alloys have a powerful antimicrobial effect capable of blitzing both bacterial superbugs - like MRSA - and even some viruses, like the flu, as he explained to Chris Smith...

Bill - Humans are very tactile people - we don't wash our hands very often.  So what that means is we might go to the toilet, and particularly men do not wash their hands, and then they walk around touching contact surfaces such as door handles, push plates, stair rails, things like then and then, if someone else comes and touches that surface, they can pick up the bugs.

Chris - How long with MRSA remain on some of these surfaces? You've talked about push plates on doors, door handles.  How long will it stay there in a viable state so a person coming along could pick it up?

Bill - Oh, we're talking of very tough bugs here - they will survive weeks on a dry surface.  And the problem is, of course, how often do we clean any surfaces, even in hospitals.  We don't have 27/7 protection just from standard cleaning practices, so that's why we're interested in antimicrobial metals such as copper.

Chris - And how do they work - what have your found?

Bill - Copper's a very interesting metal.  It's actually quite reactive and we've found that with bacteria, it stops the bacteria respiring - so they stop breathing - it can punch holes in their cell membranes so that their constituents leak out, and it can destroy their DNA.

Chris - How did you actually find this?  What were the experiments were you doing to show that this is the case?

Bill - Well because we're interested in touch surfaces, we developed a model system where we simulated a hand touch onto a surface and put in several million MRSA onto those surfaces.  They started to die literally as soon as they touched the surface.

Chris - How do you think the copper is doing this - do you know?

Bill - Yes, copper is a very reactive metal - it takes part in oxidation reduction reactions.  So, for example, when it punches holes in bacterial cell membranes - they're made of lipid, a kind of fat, and the copper oxidises that lipid and that, effectively, punches holes into the lipid membrane.  The copper also forms reactive oxygen species and these species, molecules such as peroxide, superoxide, hydroxyl radical, attack and destroy proteins, attack and destroy fats, lipids and they attack and destroy DNA.

Chris - Your hypothesis then is that when the bugs are on that surface, the copper is producing all of these chemicals, the bugs find themselves in a really hostile environment and it just destroys them.

Bill - Absolutely correct.  And, in fact, we have microscopy procedures where we can use special fluorescent stains and you can actually see the production of these reactive oxygen species in real time as the bacterial touch down on the copper surface.

Chris - Has anyone tried doing the experiment for real - putting these sorts of treated surfaces into a hospital environment and seeing if it does cut down infection rate?

Bill - Well yes.  It's been very exciting that partly out of the lab work we started, people have been putting different copper alloys in hospitals all over the world and, in every case, they're reporting something like a 90% reduction in the number of bugs you can actually detect on the copper surfaces.  And what's really exciting - a study was undertaken -  two hospitals in New York, one in Charleston and there, looking at all the data, they're reporting a 58% reduction in infection rates.  So I think that's a classic example of translation from the laboratory into the real world setting.

Chris - Are researchers and technologists not already using silver in the same sort of way?

Bill - Well that's an interesting one because if you ask anyone, particularly in the clinical field, name and antimicrobial metal, they might suggest silver but, in fact, we've done comparable experiment comparing it with copper.  You can put MRSA onto a dry silver surface and the MRSA survives quite nicely for 24 hours.

Chris - So what are you advocating then?  We go back to the good old Victorian days of copper and brass doorknobs on every door and this would solve the problem?

Bill - Well, the Victorians were not completely stupid.  It's certainly interesting that there was an American physician, Phyllis Coon, that 25 years ago, she noticed that when they started to take the brass door handles and push plates out of her hospital, the infection rate started to go up. She actually warned people back then that this might be a problem.  So we're not saying go back to brass - I think you go back to one of these modern alloys and, of course, the architects love this now because the alloys have got a whole range of different colours and textures so they're really starting to switch on to this as well.


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