What is MRSA?

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MRSA stands for methicillin-resistant Staphylococcus aureus. There are various sub-types (strains) of S. aureus and some strains are classed as MRSA. MRSA strains are very similar to any other strain of S.aureus That is, some healthy people are carriers, and some people develop the types of infections described earlier.

Most S. aureus infections can be treated with commonly used antibiotics. However, MRSA infections are resistant to an antibiotic called methicillin and also to many other types of antibiotics. Resistance means that the bacteria are not killed by the antibiotic.

MRSA has become much more common since the 1980s. MRSA is now the cause of over 4 in 10 bloodstream infections with S. aureus.

How serious is an MRSA infection?

MRSA strains of bacteria are no more aggressive or infectious than other strains of S. aureus. However, infections are much more difficult to treat because many antibiotics do not work. Therefore, infections tend to become more severe than they may otherwise have been if the cause of the infection is not diagnosed early, and antibiotics that do not work are given at first.

Who gets MRSA?

MRSA occurs most commonly in people who are already in hospital, especially if they have been in hospital for a length of time. Some wards in the hospital have higher rates of MRSA (for example intensive care units) than others. People who are more prone to MRSA are those who are very ill or have wounds or open sores (for example bed-sores or burns). The wounds or sores may become infected with MRSA and the infection is then difficult to treat. Infections which start in the skin may spread to cause more serious infections. Also, urinary catheters and tubes going into veins or other parts of the body ('drips' etc) are sometimes contaminated by MRSA and can lead to urine or blood infection.

MRSA can also cause infections in people outside hospital, but much less commonly than in hospitalised people.

MRSA can affect you in two ways; either you are a carrier of MRSA or have an infection caused by MRSA.

MRSA colonisation (carrier of MRSA)

This is when MRSA grows in or on your body with no signs or symptoms of an infection. Many people carry MRSA without it causing any symptoms whatsoever. The most common place for colonisation are your armpits, nostrils, skin (especially if you have eczema), throat and urine. This colonisation can act as a reservoir which means that MRSA infections can later either develop in your body or spread to other people.

If you know you are a carrier of MRSA and are due to go into hospital, for example for an operation, then you should let the hospital know before you go in. This will not necessarily delay or prevent your admission.

If you are found to be a carrier of MRSA then you are likely to be offered treatment which will then prevent future infections or the spread of MRSA. This treatment is usually in the form of ointment to put inside the nose or antiseptic washes, depending on where the bacteria have been found on your body. It is still uncertain from clinical trials as to which treatment is the most effective.

MRSA infection

Infections with MRSA are usually associated with high fevers and signs of the infection. As mentioned, most commonly these are infections of the skin and soft tissues (like boils and abscesses). Less commonly, MRSA can cause pneumonia and urine infections.

- Next: how is MRSA diagnosed?