Frequently-touched surfaces in busy areas - such as hospitals, transport hubs and public buildings – are at high risk of community-acquired and healthcare-associated infections (HCAIs) caused by methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive Staphylococcus aureus (MSSA). Bacteria deposited on a surface by one person touching it, or through contaminated body fluids, can be picked up by subsequent users and spread to other surfaces, potentially causing thousands of infections worldwide. There were more than 800 cases of MRSA and almost 10,000 cases of MSSA reported by English NHS acute Trusts between 1 April 2014 and 31 March 20151.
In previous studies at Southampton, simulated 'droplet contamination' of MRSA – representing a sneeze or a splash – showed that it was rapidly killed on copper and copper alloy surfaces. But contamination of surfaces often occurs through fingertips drying rapidly and potentially being overlooked by cleaning regimes, unlike visible droplets.
Dr Sarah Warnes, lead author of the new research, said: 'Our latest research shows that in simulated fingertip contamination of surfaces with millions of MRSA or MSSA, the cells can remain alive for long periods on non-antimicrobial surfaces – such as stainless steel – but are killed even more rapidly than droplet contamination on copper and copper alloys. Exposure to copper damages the bacterial respiration and DNA, resulting in irreversible cell breakdown and death.'
This new paper, published in the journal Applied and Environmental Microbiology, demonstrates that MRSA die on copper surfaces by a multifaceted attack from copper ions and reactive oxygen species (ROS).
Professor Bill Keevil, Chair in Environmental Healthcare at the University of Southampton and the paper's co-author, explained the significance of these findings: 'It's important to understand the mechanism of copper's antimicrobial efficacy because microorganisms have evolved various mechanisms to convey resistance to disinfectants and antibiotics. Our work shows that copper targets various cellular sites, not only killing bacterial and viral pathogens, but also rapidly destroying their nucleic acid genetic material so there is no chance of mutation occurring and nothing to pass on to other microbes, a process called horizontal gene transfer. Consequently, this helps prevent breeding the next generation of superbug.'
1. Staphylococcus aureus (MRSA and MSSA) bacteraemia mandatory reports. Summary of the Mandatory Surveillance Annual Epidemiological Commentary, 2014/15 Public Health England, July 2015
