City hospitals the main breeding ground for MRSA, study reveals

Infection is being spread from large hospitals to community facilities, Scottish scientists discover

Scientists at the University of Edinburgh have discovered a link between MRSA prevalence in large city hospitals and the spread of infection to smaller community medical facilities

Large city hospitals are believed to be the main breeding ground for the life-threatening superbug, MRSA, new research has shown.

A study by scientists at the University of Edinburgh identified that, in the main, MRSA infections started in larger general hospitals, before being spread around smaller hospitals and community facilities as patients were discharged or transferred.

For example, researchers traced the bug from a large city hospital in London to smaller units across the South East. Similarly, the infection shifted from Glasgow in the west of Scotland to the East of the country.

Lead researcher, Dr Ross Fitzgerald of The Roslin Institute at the university, said: “The high levels of patient traffic in large hospitals means they act as a hub between patients, who may then be transferred or treated in regional hospitals.”

The scientists looked at the genetic make-up of more than 80 variants of a major clone of MRSA found in hospitals. Known as EMRSA-16, this clone is the most common type of MRSA identified in the UK and only occurs in hospital settings. The investigators estimated it had been around on UK wards for some 35 years, and they identified mutations and genetic elements that may have allowed it to spread within hospitals.

The high levels of patient traffic in large hospitals means they act as a hub between patients, who may then be transferred or treated in regional hospitals

They made the discovery about its transference into the community by tracking movements using this genetic code as a tag.

This knowledge may now enable the development of new ways to prevent the spread of MRSA, and a number of other potentially-deadly healthcare associated infections. For example, patients could be screened and treated for MRSA before transferring from one hospital to another. This is currently not universal policy, although most patients are swabbed before being admitted to hospital for a planned medical or surgical procedure.

Dr Fitzgerald said: “This is the first time we have had genetic evidence for the spread of MRSA, and if we can identify the transmission routes, we can take steps to prevent spread."

Health Protection Agency clinical scientist and co-author of the paper, Dr Angela Kearns, added: “This type of information is important to help us develop policies to improve public health.”

This is the first time we have had genetic evidence for the spread of MRSA, and if we can identify the transmission routes, we can take steps to prevent spread

MRSA first began to appear in UK hospitals around 50 years ago following the widespread introduction of antibiotics, to which the bacteria is becoming increasingly resistant.

The paper, published in the journal, PNAS , also found evidence that the MRSA strain studied evolved from antibiotic-sensitive bacteria that existed more than 100 years ago.

The researchers are now calling for a more indepth study looking at whether the pattern of spread identified in Glasgow and London is reflected in other areas around the country.

Fellow researcher, Paul McAdam, said: “Our findings suggest that the referral of patients to different hospitals is a major cause of MRSA transmission around the country. This knowledge could help in finding ways to prevent the spread of infections.”

The research was funded by the Chief Scientist Office, Scottish Government Health and Social Care Directorates, the Medical Research Council, and the Biotechnology and Biological Sciences Research. It involved collaboration between The Roslin Institute, the Wellcome Trust Sanger Institute and the University of Bath in the UK, and the Broad Institute and the University of Mississippi Medical Centre in the United States.