MRSA spread from city to regional hospitals tracked with genetic tags

The emergence and spread of MRSA (Methicillin Resistant Staphylococcus Aureus) in the UK has been tracked thanks to genetic analysis of samples taken from infected patients over a 53-year period.

The study, published in the journal PNAS (Proceedings of the National Academy of Sciences), suggests that hospitals in large cities act as breeding grounds for new, increasingly resistant variants of the superbug. Patients then carry these new MRSA strains to regional centres when they are transferred.

Lead researcher Dr Ross Fitzgerald, of the Roslin Institute at the University of Edinburgh, said that 'the high levels of patient traffic in large hospitals mean they act as a hub for transmission between patients'. This scenario had previously been suggested to explain the spread of the bacteria but, Dr Fitzgerald told the BBC, 'this is the first time we have had genetic evidence for it'.

The study centred on EMRSA-16, the commonest type of MRSA in the UK, which emerged 35 years ago and only occurs in hospitals. By identifying mutations in the various samples scientists were able to trace the spread of the disease around the country.

In London new variants spread from the larger, central hospitals to centres in the south of the UK while Glasgow was identified as a hub for disease transmission to the north and east of Scotland.

Paul McAdam, the first author on the paper, and a PhD student at the Roslin Institute, said that the study 'could help in finding ways to prevent the spread of infection'. Currently screening and treating patients for MRSA is not universal practice across the NHS although all hospital patients scheduled for a procedure are offered a simple swab test.

The Daily Mail highlighted a recent report in the British Medical Journal which revealed a dramatic decrease in the prevalence of MRSA since a peak in reported cases a decade ago. The initiative encouraging healthcare workers to wash their hands between patient consultations 'had saved more lives than any medical development for a generation', the newspaper said.