Copper’s role in tackling superbugs
Southampton researchers have discovered the role that copper can play in eliminating healthcare associated infections (HAIs) and their findings are proving influential across the world.
According to the government sponsored O’Neill Report, the global cost of failing to tackle the threat posed by antimicrobial resistance could be the loss of 10 million lives and $100trn by 2050. The report, published in May 2016, suggests that proactive solutions to slow down the rise of drug resistance should include improving hygiene and sanitation, thereby reducing HAIs.
Healthcare-associated infections cause a range of symptoms, from minor discomfort to serious disability, and even death. The World Health Organization reports that HAIs already affect seven million people globally per year. High standards of infection control are crucial for containing the spread of these infections. But despite widespread hand washing campaigns and improvements in cleaning, infection rates remain unacceptably high. As new strains of bacteria and viruses emerge and spread from hospitals to schools, homes and public transport, or vice versa, researchers face a constant ‘arms race’ to find new solutions.
Professor Bill Keevil, Head of the Microbiology Group and Director of the Environmental Healthcare Unit at the University of Southampton, has spent considerable time researching HAIs. His team has discovered that the natural antimicrobial properties of copper and copper alloys dramatically reduce the presence of methicillin-resistant Staphylococcus aureus (MRSA) compared with stainless steel, which is commonly used on surfaces in hospitals. “Although stainless steel looks like a mirror surface to the naked eye, under the microscope it’s full of scratch marks, and bacteria are able to hide in the grooves,” says Bill. “The reason it’s used is that it’s deemed to be easy to clean and disinfect, but if you look at a magnified image of the surface, you can see that this is not the case.”
Once we saw how effective copper could be, we started talking to the Department of Health in the UK and the National Institutes of Health in the USA about doing ward trials
Researchers have found that MRSA bacteria remain fully active for days on stainless steel surfaces, whereas on brass (an alloy of copper and zinc), they die in less than five hours on a moist surface and on pure copper they are eliminated in under 30 minutes. On a dry surface this happens in just a few minutes.
How copper kills
The Southampton research team has shown that copper works in several different ways to shut down bacterial cells’ chemistry and physiology. Using ‘quenching agents’ to inhibit the action of copper, the team worked out that the metal releases positively charged ions and reactive oxygen species, which quickly kill any bacterial cells that touch it.
“We have seen that copper completely destroys the bacteria’s DNA in minutes so they can’t go on to become resistant,” says Bill.
Copper destroys not only chromosomal DNA, but also plasmids, which are circular pieces of DNA that confer antibiotic resistance. These plasmids can move between bacteria, passing on the antibiotic resistance to different bacterial species. Copper therefore not only kills these agents, but also prevents mutation and resistance transfer to other potential superbugs.
Taking on the superbugs
The Southampton team has been investigating the antimicrobial properties of copper for over 10 years, and the University is the leading centre for this research in the UK. “Over the years this work has developed into a multidisciplinary activity,” says Bill. “The initial research was done by microbiologists, and we now work with engineers for advice on the metallurgy, as well as clinicians and infection control nurses.”
In early laboratory trials, the team showed that copper killed 10 million MRSA, Clostridium difficile and Acinetobacter baumannii bacteria in 45 minutes to two hours. When they adjusted their assays to the low concentrations of MRSA reported in hospital environments, they found that the copper killed all the bacteria much faster – in just 10 to 15 minutes. “Once we saw how effective copper could be, we started talking to the Department of Health in the UK and the National Institutes of Health in the USA about doing ward trials to find out whether our results in the lab would translate into real benefits in hospitals,” says Bill.
In 2009, the researchers conducted a trial at Selly Oak Hospital in Birmingham, UK, in which all the fixtures and fittings – such as door handles and light switches – in one ward were replaced with copper. The trial, funded by an education grant from the UK’s Copper Development Association, showed that the copper fittings reduced the numbers of viable organisms on the copper surfaces by more than 90 per cent. This trial has now been repeated in the USA, South Africa, Japan, Germany and Chile, with similar results. “Our colleagues in the USA recently reported that copper alloy touch surfaces caused a 58 per cent reduction in infection rates in a new hospital trial. This is very exciting because it means that, as a research community, we have now shown in several separate studies that copper is effective at reducing microbial contamination and infection,” says Bill.
There have been further exciting developments, with the discovery that copper can help to prevent the spread of respiratory viruses, which are linked to severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS). One such virus – human coronavirus 229E – can survive on surface materials including ceramic tiles, glass, rubber and stainless steel for at least five days. However, research at Southampton has shown that with exposure to copper, the virus is inactivated within a few minutes, before being completely and irreversibly destroyed.
The team’s research is already having an impact. Hospitals in countries around the world, including the US, Spain, Brazil and Japan that have been convinced by the science, are already starting to incorporate copper alloys into their wards. The ECRI Institute, a world leader in researching the best approaches to patient care, which influences more than 5,000 healthcare organisations worldwide, included antimicrobial copper in their Top 10 Hospital C-Suite Watch List 2014.
The benefits are being recognised beyond the healthcare sector. Poland’s newest electric city bus is the world’s first to feature handrails made from antimicrobial copper while Congonhas Airport, one of Brazil’s busiest airports has been kitted out with antimicrobial copper touch surfaces, including handrails and counters. Similar examples can be found across sport and leisure, education and public sector, commercial and industrial sectors. With the threat posed by drug-resistant infection firmly on the public radar, Southampton researchers are at the forefront of finding solutions.
For more information on Bill's research
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