MRSA infection - Causes 

Causes of MRSA infection 

MRSA is caused by strains of bacteria that have developed resistance to a number of widely used antibiotics.

How MRSA spreads

MRSA bacteria are usually spread through skin-to-skin contact with someone who has an MRSA infection or who is colonised by the bacteria. Colonised means bacteria are present on your body but do not cause any symptoms.

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

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

MRSA in hospital

It's more common for someone to develop MRSA while they are in hospital or a care home (known as healthcare-associated MRSA - HA-MRSA). This is because people in hospital:

  • often have a point that allows bacteria to enter their body, such as a surgical wound, burn, catheter (a tube used to drain away urine) or an intravenous tube - if a patient who is colonised with MRSA bacteria touches their wound or catheter tube, they may infect themselves
  • tend to be older and have more complex health problems than the general population - which makes them more vulnerable to infection
  • are surrounded by a large number of people, both patients and staff - this makes it is easier for bacteria to spread from person to person, or from a person to an object and then to another person

Who is at risk?

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

  • a weakened immune system, for example in elderly people, newborn babies and people with a long-term health condition, such as type 2 diabetes
  • an open wound
  • a catheter or an intravenous drip
  • a burn or cut on the skin
  • a severe skin condition, such as a leg ulcer or psoriasis
  • surgery
  • are taking frequent courses of antibiotics

MRSA infections usually develop in people being treated in hospital, particularly patients in intensive care units (ICUs) and on surgical wards.

MRSA in the community

MRSA contracted outside hospitals is known as community-associated MRSA (CA-MRSA). It's much less common than HA-MRSA.

However, in recent years the number of cases has increased and could continue to increase in the future. The following factors increase your risk of getting CA-MRSA:

  • living in a very crowded environment - for example a military base, prison or student hall of residence
  • frequent skin-to-skin contact - outbreaks of CA-MRSA have been reported in people who play contact sports, such as rugby
  • cut or grazed skin - this is more vulnerable to infection, as are people who regularly inject illegal drugs, such as heroin
  • contaminated items and surfaces - places where many people share utensils, tools or where many people are likely to touch the same surfaces
  • lack of cleanliness - outbreaks of MRSA can occur in homeless people or in people on active military duty who have limited access to cleaning facilities
  • previous use of antibiotics

Page last reviewed: 13/06/2013

Next review due: 13/06/2015

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Keep your home clean

How good home hygiene can help prevent the spread of infectious diseases such as MRSA, E. coli and Clostridium difficile