Copper anti-microbial materials are more effective in hospitals than silver, study finds
Silver and copper have been used for their antimicrobial properties for centuries. Manufacturers are now incorporating these metals into healthcare, the food industry and some consumer products, and claiming that they exhibit antimicrobial efficacy. Several companies have created silver-ion coatings that can be applied to various surfaces, from work surfaces to door handles, which are then marketed as antimicrobial; some products also claim to be effective against the hospital-acquired infection MRSA.
Researchers from the Copper Development Association in New York and the School of Biological Sciences at the University of Southampton in the UK have compared antimicrobial materials containing silver and copper in real-life conditions. The results of their study are published in Letters in Applied Microbiology.
Materials containing silver-ions have been shown to be effective in high temperatures (35°C) and high humidity (90% or higher relative humidity), but until this study, they had not been tested at lower temperatures, nor at humidity levels typically found in indoor environments such as hospitals. The researchers used copper alloys as a point of comparison because laboratory testing has shown that they are effective in reducing more than 99.9% of bacteria within two hours at room temperature (22°C) and normal humidity.
The study tested survival rates of MRSA on two types of silver-ion coated surfaces, five copper alloy surfaces and a stainless steel surface. The silver-ion materials showed only minimal bacterial reduction at 20°C and 22% humidity. The stainless steel, which served as the experimental control, showed no measurable antimicrobial efficacy at any temperature or humidity level, as was expected.
Previous laboratory studies have demonstrated copper’s broad-spectrum antimicrobial efficacy at room temperature and humidity against bacteria (MRSA, Clostridium difficile), fungi (Aspergillus niger) and viruses (including influenza A (H1N1)). Following a review of such detailed scientific data, copper has been officially recognised by the US Environmental Protection Agency. Copper, brass and bronze alloys have also been registered to make public health claims. Copper’s antimicrobial performance in the laboratory, under typical indoor conditions, has resulted in a clinical trial that is taking place at Selly Oak Hospital in Birmingham. The first results showed a 90–100% reduction in bioburden on copper alloy surfaces (door handle, push plate, toilet seat) compared with non-copper surfaces. Clinical trials are also ongoing in the US, Germany and Chile.