Community-acquired MRSA spreads

Apr 1 2008

Drug resistant hospital superbugs like MRSA have been kept under control in Denmark for more than 30 years.

But the latest reports say that in the last 10 years MRSA cases have risen 10 times as new strains of bacteria with resistance genes spread through the community, scientists heard today (Tuesday 1 April 2008) at the Society for General Microbiology's 162nd meeting being held this week at the Edinburgh International Conference Centre.

“The new threat is MRSA transmission in the community, without infected people visiting a hospital or care home themselves, where they might be expected to risk contact with drug resistant bacteria”, says Professor Robert Skov from the Statens Serum Institut in Copenhagen, Denmark.

“The spread of community acquired MRSA among the general population creates a huge problem for us”, says Professor Skov. “Some infected people will inevitably be hospitalised themselves, or visit friends and relatives who are patients in hospitals. Or they could be health care workers and so will increase the risk of outbreaks of these new types of MRSA. These community strains have evolved independently of the hospital strains and so present a whole new series of problems for control and treatment”.

Staphylococcus aureus is common and usually harmless, it is carried by 25-40% of the population on their skin and in their noses. But if it gets inside the body through an injury, cut, surgical operation or through a catheter it can cause infections. These infections are often mild, causing boils or pimples, but in some cases they may develop into more serious infections affecting the bloodstream, joints and bones.

These serious infections were first brought under control with the discovery of penicillin, but as resistance to antibiotics has spread, new and dangerous superbug strains such as MRSA have emerged. These are far more difficult to treat and can cause life-threatening infections, especially in patients with impaired immune systems or low white blood cell counts.

“We have managed to hold the frequency of MRSA cases down to under one per cent in Denmark for over 30 years. But in 1997 we recognised the first cases of community acquired MRSA, a new strain independent of hospital and nursing home contacts, in a young adult and two families in a rural town”, says Professor Skov. “From the families we traced the superbug being transmitted through a kindergarten, a school, a factory and a farm. Between 1999 and 2006 the number of community acquired MRSA infections increased from 11 to 175 a year, making up more than 22% of all MRSA infections, as a rising proportion.”

The Danish scientists found that the most common method of superbug transmission was from one family member to another, with children and younger adults most affected. And many of the infected families had relations in other countries with a high incidence of MRSA in the population.

The Danish health system responded by introducing new national guidelines in November 2006 designed to prevent MRSA spreading, including increased barrier precautions and isolation nursing in both hospitals and nursing homes. The guidelines appear to be successful, as a small decrease in cases has been observed. The results of these experiences, which have helped to stop the rising epidemic of MRSA, will be published in health journals shortly.