Methicillin-resistant Staphylococcus aureus (MRSA)

What is Staphylococcus aureus and MRSA?

Staphylococcus aureus (S. aureus) is a bacterium that can commonly live on the skin or in the nose or mouth of people (colonisation) that causes community and healthcare related infections around the world.

Some strains of S. aureus have developed resistance to antibiotics, and these are known as methicillin-resistant Staphylococcus aureus (MRSA). MRSA are resistant to methicillin (a derivative of penicillin) and other closely related antibiotics (oxacillin, flucloxacillin). They may also be resistant to a number of other antibiotics (sometimes referred to as multi-resistant strains).

People with MRSA colonisation can be asymptomatic. The pathogenic potential of S. aureus ranges from mild skin infections (for example boils) to serious deep infection such as osteomyelitis, and potentially fatal systemic illness such as bloodstream infection.

MRSA are important hospital pathogens that can cause significant infections in susceptible patients.

In hospital, people who have lowered resistance or who have breaks in their skin due to surgery, indwelling devices or chronic wounds, may be predisposed to either MRSA colonisation or infection.

Mode of transmission

Numerous reports of hospital outbreaks of MRSA have shown that patient-to-patient transmission of MRSA is common. The most likely modes of transmission are:

• direct contact - by the contaminated hands of staff and/or visitors
• indirect contact - by contact with contaminated equipment or surfaces

Patients who are colonised may also self-infect areas of broken skin, or medical device insertion sites.

Prevention

The prevention of infection with MRSA involves the simultaneous application of a number of strategies:

• standard and transmission-based precautions
  
• identification of carriage (screening of high risk patient groups) and appropriate inpatient placement, for example a single room
• diligent hand hygiene practices e.g. as per the 5 moments for hand hygiene, access to hand hygiene facilities and the availability of alcohol-based hand rubs at point of care
• appropriate use of personal protective equipment when performing patient care activities
• appropriate cleaning and disinfection of patient surroundings and medical equipment
• antimicrobial stewardship which ensures that antibiotics are prescribed appropriately.

Management

Hospitals and healthcare settings should have a strategy for management of MRSA colonisation and infection with practices adapted to suit the clinical setting. For example, management of patients identified with MRSA in an intensive care unit may be different to management of a patient attending an outpatient department where the risk of transmission and infection are lower.

Some patients may benefit from decolonisation treatment with mupirocin nasal ointment and medicated body washes. See the Staphylococcus aureus Patient Decolonisation consumer information fact sheet (PDF 363KB).

Further information

For further information on MRSA see the MRSA Guideline (PDF 766KB), the MRSA healthcare worker fact sheet (PDF 71KB) or contact SA Health's Infection Control Service.