MRSA superbug much more common in U.S. than UK

NEW YORK (Reuters Health) - The antibiotic-mocking MRSA bacteria seem to be thriving better in the US than in the UK, according to new government data.

They show Americans are more than six times as likely as Britons to contract the superbug in the community, although rates of hospital infections are about the same.

"This is the first time we compared rates of MRSA bloodstream infections between US and England," said Dr. Fernanda Lessa, of the Centers for Disease Control and Prevention in Atlanta. "So, the findings are new to us."

That's despite the fact that MRSA -- or methicillin-resistant Staphylococcus aureus -- was first discovered in the UK and didn't make it across the Atlantic until several years later.

It is estimated that, in 2005, it caused severe infections in nearly 95,000 Americans, killing more than 18,500 of them.

According to the new government statistics, published in the journal Clinical Infectious Diseases, about 29 per 100,000 people in the US contract a MRSA bloodstream infection every year, compared to 11 Britons.

And when looking only at infections presumed to be acquired outside of hospitals, the difference was even bigger: 22 cases per 100,000 in the US and 3.5 in the UK.

"It underlines once again that MRSA is a problem that we need to take more seriously," said journalist Maryn McKenna, who published a book, SUPERBUG, about the bug earlier this year.

The question is, why the big difference?

The study tapped into data from the US Centers for Disease Control and Prevention and the UK Health Protection Agency, and differences between the two surveillance systems could be involved.

But other factors might be at play, too, CDC's Lessa told Reuters Health by e-mail.

For instance, more than three-quarters of Americans with community-onset MRSA had been in recent contact with the healthcare system. Infected Americans were twice as likely as Britons to have been on dialysis, and they more commonly had diabetes or had had a central intravenous line inserted by a health provider.

This hints differences in both medical care and patient type between the two countries are important, the researchers say. More patients are on dialysis for renal failure in the US than in the UK, and the CDC reported in 2007 that MRSA infections were 100 times more common in such patients than in the general population.

McKenna said it was unclear where the bacteria that attack dialysis patients come from.

"We don't know whether they have a hospital strain from a healthcare institution or if they are carrying a community strain that only enters the body when the skin is broken," she told Reuters Health.

People can carry MRSA on their skin or nostrils without getting sick. But when their skin is pierced by a health provider inserting an IV line, the bacteria gain easy access to the blood. Or they may jump to other patients with compromised immune systems.

McKenna said the US had been lagging behind European countries in terms of infection control.

The Netherlands, for instance, has long been screening people for MRSA before admitting them to hospitals. If they carry the bug, they are quarantined so they won't infect others.

While some hospitals in the US have recently implemented such a system, too, they are few and far between, said McKenna.

Still, over the past decade US hospitals have introduced several measures aimed at preventing the spread of infectious disease, such as requiring staff to wash their hands with soap before inserting a catheter into a patient.

And it's possible they are paying off, according to a CDC report earlier this year that showed hospital MRSA infections had dropped since 2005 (see Reuters Health story of Aug 11).

"Great strides have been made in reducing rates of MRSA bloodstream infection in United States hospitals," said Lessa, "and we need to expand this success."

SOURCE: link.reuters.com/duk49p Clinical Infectious Diseases, October 15, 2010.