The MRSA (methicillin-resistant Staphylococcus Aureus) Problem
Dr Mark Farrington Chris - We are told that
MRSA kills 5000 people per year. What is MRSA and where did it come from?
Mark - MRSA, or Methicillin Resistant Staphylococcus aureus, is a special variety of a very common bacterium. We come into contact with it every day, and a third of us have Staphylococcus aureus up our noses all the time! MRSA is just a small group of this bacterium that has become resistant to a common type of antibiotics. The bacteria itself isn't particularly nasty; it is just more resistant to treatment, which has implications when trying to find ways of preventing and treating infection. The problems Staphylococcus would cause on a day to day basis are wide ranging, and are one of the commonest causes of infection in normal healthy people. When we have a cut, it is usually our own Staphylococcus that infects us. The MRSA strain was first found early 1960s, which was the same time that the antibiotic methycillin was introduced. The reason there were a few isolates of the resistant strain so early on is probably due to methicillin being related to beta-lactin. Beta-lactin is a natural antibiotic produced by fungi; probably used as defence against bacteria. Therefore, Staphylococcus has been in contact with the antibiotic for a long time, allowing a few resistant strains to evolve. It is only since people have been repeatedly prescribed antibiotics that problems have arisen. The non-resistant strains die out, leaving the resistant strains behind.
Chris - When did MRSA become a big problem in hospitals?
Mark - it actually took quite a long time. For many years, the bacteria were only found occasionally, and only slightly more often in people in hospital than people not in hospital. MRSA started to appear in clusters of people in nearby beds, but the outbreaks were still small. The problem has increased as the resistant bacteria has been passed from patient to patient. The most significant method of transmission is via the hands of healthcare workers in general, not just doctors. If a patient has MRSA on their skin and receives care from a member of staff who forgets to wash their hands, the next patient they treat will have the bacteria passed onto them. It is important to distinguish between being colonised by bacteria and being infected by bacteria.
Studies have shown that people visiting hospital acquire a range of bacteria different from those they came in with. However, they do not develop a similar range of infections: having MRSA on your skin does not necessarily mean that you will become ill.
December 2004
