What is Staphylococcus aureus?

Staphylococcus aureus is a bacterium (germ). It is often just called ‘S.aureus’ or staph’. S. aureus bacteria are often found on the skin and in the nose of healthy people. In fact, about 3 in 10 people have S. aureus bacteria living on (colonizing) their skin. These people are called S. aureus carriers’. In healthy people who are carriers‚ S. aureus is usually harmless.

However‚ S. aureus bacteria sometimes invade the skin to cause infection. This is more likely if you have a cut or graze which can allow bacteria to get under the surface of the skin. S. aureus is the cause of skin infections such as boils‚ pimples‚ impetigo‚ skin abscesses‚ and is a common cause of wound infections.

In some people‚ S. aureus can sometimes get into the bloodstream and travel to internal parts of the body to cause more serious infections. For example‚ blood poisoning (septicemia)‚ lung infection (pneumonia)‚ bone infection (osteomyelitis)‚ heart valve infection (endocarditis)‚ etc. These serious infections are more likely to occur in people who are already unwell or debilitated‚ or who have a poor immune system. These infections need to be treated with antibiotics.

What is MRSA?

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 above. The difference is that most S. aureus infections can be treated with commonly used antibiotics. In recent years some strains of S. aureus have become resistant to some antibiotics. Resistance’ means that the organism is not killed by the antibiotic. MRSA strains are not only resistant to the antibiotic called methicillin‚ but also to many other types of currently existing antibiotics.

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 are ineffective. Therefore‚ infections tend to become more severe.

Who gets MRSA?

MRSA occurs most commonly in people who are already in a hospital. People who are more prone to it are those who are very ill‚ or have wounds or open sores such as 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 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 hospitalized people.

How common is MRSA?

As mentioned‚ being a carrier of S. aureus and infections with S. aureus are very common. The number of cases due to MRSA strains is not known‚ but it is becoming an increasingly common problem.

How is MRSA diagnosed?

If an infection with S. aureus is suspected then‚ depending on the type of infection‚ a sample of blood‚ urine‚ body fluid‚ or a swab of a wound can be sent to the lab’ for testing. If S.aureus is detected‚ further tests are done to see which antibiotics will kill the bacteria. MRSA strains can be identified by seeing which antibiotics kill the bacteria found on testing. Healthy people suspected of being carriers of MRSA can have a swab or the nose or skin taken and tested.

How is S.aureus and MRSA spread?

S.aureus bacteria (including MRSA strains) spread from person to person usually by direct skin–to–skin contact. Spread may also occur by touching sheets‚ towels‚ clothes‚ dressings‚ etc‚ which have been used by someone who has MRSA. However‚ as mentioned‚ S. aureus (including MRSA strains) will not normally cause infection if you are well. The bacteria may get onto your skin‚ but do no harm. So‚ for example‚ people who visit patients with MRSA‚ or doctors and nurses who treat people with MRSA‚ are not likely to develop an MRSA infection. But‚ they may become contaminated’ with the bacteria and may pass it on to someone who is ill‚ or who has a wound‚ who then may develop infection.

What is the treatment of MRSA infections?

MRSA infections are usually treated with antibiotics. (Boils or abscesses caused by MRSA may only need to be drained and may not need antibiotics.) However‚ the choice of antibiotics is limited as most antibiotics will not work. Many MRSA infections can only be treated with antibiotics that need to be administered directly into a vein. The course of treatment often ranges from several days to weeks.