Doctors stop superbug MRSA in its tracks with DNA testing

Nov 14, 2012

Inexpensive technique identified source of infection in a hospital - and could be used against E. coli and salmonella

BRITISH doctors have stopped an outbreak of the 'superbug' MRSA in a hospital by using DNA sequencing to trace the source the infection to an unsuspecting member of staff.

The relatively simple and inexpensive technique could prevent thousands of lives being lost and save the NHS millions of pounds. It might also prove effective against other infections such as salmonella and E. coli.

The breakthrough came at The Rosie Hospital, which is part of Addenbrooke's in Cambridge. MRSA (methicillin-resistant Staphylococcus aureus) was detected in 12 babies.

MRSA exists harmlessly on the skin of about one per cent of people. But if it breaches the skin it can cause a life-threatening infection that is very difficult to treat.

In 2008, it was reported that the cost to the NHS of keeping MRSA patients in hospital amounted to £45m per year – and although there has been a recent decrease in infection rates in recent years, several hundred people die every year due to MRSA. In the US, it kills around 19,000 per year.

At The Rosie, doctors were unable to tell if the MRSA outbreak was being brought in by numerous sources or if it was one person.

The BBC reports that researchers at the University of Cambridge and the Sanger Institute used DNA sequencing to construct a 'family tree' of the MRSA infections and found that they were closely related and probably from the same source.

After 'deep-cleaning' the hospital, and two months without a case, MRSA was again detected. DNA tests on the new bug found it was related to the previous outbreak. After testing 154 staff, one person was found to be carrying the MRSA. After the person was treated, the outbreak came to an end.

Dr Julian Parkhill of the Sanger Institute, whose work is published in the journal Lancet Infectious Diseases, said: "We think this is the first case where whole genome sequencing has actually led to a clinical intervention and brought the outbreak to a close."

He told Reuters that fast, cheap DNA sequencing like this could form the basis for regional or national infection surveillance program that would nip infectious disease outbreaks in the bud.

"This technology holds great promise for the quick and accurate identification of bacterial transmissions in our hospitals and could lead to a paradigm shift in how we manage infection control and practice," said Parkhill. It could also be used against food-borne diseases such as salmonella and E. coli.

Professor Ross Fitzgerald, of the Roslin Institute at the University of Edinburgh, told the BBC the technique would be standard practice for any hospital within a "small number of years".

Sign up for our daily newsletter