Causes of MRSA infection 

MRSA is a type of staphylococcal bacteria that has developed resistance to a number of widely used antibiotics.

Staphylococcal ("staph") bacteria are relatively common. About 1 in 3 people carry staph bacteria harmlessly on their skin, usually inside their nose and on the surface of their armpits, groin and buttocks. This is known as being "colonised" by staph bacteria.

Up to 1 in every 30 people are colonised by MRSA bacteria. Like other types of staph bacteria, it's usually harmless and not a cause for concern for most healthy people. However, it can cause problems if it's able to enter the body or it infects someone in poor health.

How MRSA is spread

MRSA bacteria are usually spread through skin-to-skin contact with someone who has an MRSA infection or has the bacteria living on their skin.

The bacteria can also spread through contact with towels, sheets, clothes, dressings or other objects that have been used by a person infected or colonised with MRSA.

MRSA can survive for long periods on objects or surfaces, such as door handles, sinks, floors and cleaning equipment.

MRSA in hospital

You're most at risk of developing an MRSA infection when you're in hospital. This is known as healthcare-associated MRSA infection.

This is because people in hospital:

  • are surrounded by a large number of people, including patients, visitors and staff, which makes it easier for the bacteria to spread
  • often have an entry point for bacteria to get into their body, such as a surgical wound, burn, feeding tube, catheter or intravenous tube
  • tend to have more complex health problems than the general population, which makes them more vulnerable to infection

Who's most at risk?

You may be at an increased risk of developing an MRSA infection in hospital if you have:

  • a serious health condition
  • an open wound, burn or cut in your skin
  • a catheter or an intravenous drip
  • a long-term skin condition, such as a leg ulcer or psoriasis
  • recently had surgery
  • been taking frequent courses of antibiotics that aren't effective against MRSA

Patients treated in intensive care units (ICUs) and surgical wards are at a particularly high risk of developing an infection.

MRSA outside of hospital

Although it's much less common, it's also possible to develop an MRSA infection outside of hospital. This is known as community-associated MRSA infection.

It's generally less serious than healthcare-associated MRSA, and in most cases just affects the skin or soft tissues.

The following factors increase your risk of getting an MRSA infection outside of hospital:

  • living in a crowded environment – such as a military base, prison or student hall of residence
  • frequent skin-to-skin contact – outbreaks of MRSA have been reported in people who play contact sports, such as rugby
  • having a cut or grazed skin – this can allow the bacteria to enter the body
  • sharing contaminated items and surfaces – utensils, tools and surfaces can become contaminated with MRSA, and anyone touching this could pick up the infection
  • poor hygiene – you're more likely to get MRSA if you don't wash your hands regularly and don't clean and cover breaks in your skin

Your GP can carry out a swab to test for MRSA if they suspect it's the cause of your infection.

Page last reviewed: 28/04/2015

Next review due: 28/04/2017