Methicillin-resistant Staphylococcus aureus (MRSA)

Staphylococcus aureus (sometimes referred to as "golden staph") is a bacterium that causes community and healthcare related infections around the world. 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. It is commonly found in the nose and on the skin of humans and occasionally in some animals (for example pigs, dogs, horses).

Antibiotic resistant strains

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).

MRSA are important hospital pathogens that can cause significant infections in susceptible patients. Although harder to treat than methicillin-sensitive Staphylococcus aureus, MRSA are no more or less virulent than sensitive strains.

People may become colonised with MRSA, where MRSA can be found in the nose or throat or on the skin, with no apparent ill effects. 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:

• identification of carriage (screening of high risk patient groups) and appropriate inpatient placement, for example a single room
• diligent hand hygiene practices, including alcohol-based hand rubs at point of care
• application 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.

Hospitals should have a strategy for management of MRSA carriage 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 much lower.

Management

Hospitals 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 ICU may be different to management of a patient attending an outpatient department where the risk of transmission and infection are much lower.

Some patients may benefit from decolonisation treatment with mupirocin nasal ointment and medicated body washes. A consumer fact sheet (PDF 108KB) explaining the procedure has been developed.

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.