Staphylococcus aureus (commonly called Staph) is a common bug or bacteria that's found on the skin and in the nostrils of about 1 in every 3 people. The bacteria usually live harmlessly on your skin and most people carry MRSA without knowing it as they have no symptoms. These people are said to be MRSA colonised or carriers. However, if these bacteria get into a wound or open cut, they can cause infections that range from boils on your skin to more severe infections of your bones, lungs and blood. These need treatment with antibiotics.
Methicillin-resistant Staphylococcus aureus (MRSA) are a group of Staph bacteria that have become resistant to commonly used penicillin-like antibiotics. This means that infections caused by MRSA bacteria require different antibiotics and can be more difficult to treat. Although they can be resistant to many of the commonly used antibiotics, there are options for treatment if you have an infection. Read more about antibiotic resistance.
Having MRSA is of particular concern in hospitals where there's a greater chance of bugs (bacteria) entering your body because of openings to your skin caused by operations, procedures and drips (intravenous lines). This puts you at risk of developing severe infections.