New strain of MRSA superbug discovered in Dublin hospitals

DICK AHLSTROM, Science Editor

Fri, Jun 03, 2011

A COMPLETELY new form of the MRSA superbug has been found in two Dublin hospitals. This new organism probably arose in animals and then jumped across to infect humans, according to the Irish researchers who discovered it.

“It is totally different. It has never been seen before in any living organism,” said Prof David Coleman of Trinity College Dublin, who led an international team that identified the bacterium.

The organism was so different that existing test kits could not recognise it as being an MRSA-type bacterium. “I have never seen anything as divergent, which means it has evolved away from humans,” Prof Coleman said yesterday.

MRSA (methicillin resistant Staphylococcus aureus) describes organisms that have developed strong resistance to most antibiotics, something that makes MRSA infections very difficult to treat in humans.

The superbug is endemic in some Irish hospitals, according to a number of studies, including a report last year, MRSA in Ireland.

It put the cost of hospital-acquired infections at €23 million per year. Those who picked up a hospital-acquired MRSA infection were seven times more likely to die than patients who did not become infected.

This new organism may add to the ongoing burden of hospital-acquired infections, given it is so very different to existing strains. “This is not just a new strain, this is absolutely and totally different from anything since MRSA was discovered in the 1960s,” Prof Coleman said.

Prof Coleman, in collaboration with the National MRSA Reference Lab at St James’s Hospital and the University of Dresden and Alere Technologies in Germany, analysed DNA taken from the bug.

They found it was genetically similar to types of MRSA found in cows and other animals, strongly suggesting the new MRSA originated in animals, he said. “The organism has crossed from an animal population into humans.”

Cases were discovered in Dublin and cases were also later found in Germany. As the study progressed, Prof Coleman’s group became aware of similar but wholly separate research into this new superbug was under way at the University of Cambridge and the Wellcome Trust Sanger Institute in the UK.

The Cambridge group found the same organism in cows and humans in the UK and in Denmark, Prof Coleman said.

For this reason the two groups published their findings simultaneously yesterday, the Irish-German team in the journal Antimicrobial Agents and Chemotherapy and the UK group in Lancet Infectious Diseases .

This new organism is similar to existing MRSAs in terms of its antibiotic resistance and virulence, he said. Unfortunately the organism can readily share its very different genetic make-up and its antibiotic resistance by passing it on to other bacteria. This means it is capable of sparking the creation of new types of superbugs.

Funding for the Irish-led research came from the Dublin Dental University Hospital Microbiology Unit.

© 2011 The Irish Times