What are Staphylococcus aureus bloodstream infections (SAB)?

Staphylococcus aureus bloodstream infections (SAB) are often associated with healthcare and occur when Staphylococcus aureus bacteria (also called S. aureus, or ‘golden staph’) cause an infection of the bloodstream, or bacteraemia. When associated with healthcare procedures, these infections are considered to be potentially preventable.

Staphylococcus aureus bacteria are frequently found on the skin or in the nose of many individuals and are commonly spread from person to person in the community. In this form they are usually harmless and most people are unaware they are carrying them.

In hospitals, Staphylococcus aureus bacteria are most commonly transmitted via the hands of healthcare workers. Bacteria from the patient’s skin or from the hand of a healthcare worker can gain direct entry into a patient’s bloodstream if they have open wounds (including incisions) or when invasive devices such as catheters are inserted. Other patients who have a greater risk of SAB infections are those with:

  • weakened immune systems (associated with cancer, or with transplant receipt, or with being very young or elderly)
  • chronic disease such as diabetes or severe underlying illness.

Are SAB infections serious?

Patients who develop bloodstream infections such as SAB are more likely to suffer complications that result in longer hospital stays and increased costs of hospitalisation. The most serious SAB infections can result in death.

Appendix A provides a definition of healthcare-associated SAB cases.

SAB resistance to antimicrobials

Antimicrobial resistance occurs when some of the germs (bacteria, viruses, or fungi) that cause infections resist the effects of the medicines used to treat them. This may lead to ‘treatment failure’, or the inability to treat the cause of the infection (Department of Health & Department of Agriculture and Water Resources, 2017).

A SAB case that is identified by a laboratory as being caused by a methicillin-resistant strain of S. aureus is referred to as MRSA. SAB caused by MRSA may cause more harm to patients and is associated with poorer outcomes as there are fewer antimicrobials available to treat the infection.

A SAB case that is identified by a laboratory as being caused by a S. aureus strain that is sensitive to commonly used antimicrobials (methicillin-sensitive) is referred to as MSSA.

The analysis and monitoring of SAB resistance to antimicrobials can inform strategies regarding the appropriate prescribing of antimicrobials with the aim of reducing resistance and adverse effects on patients.

Variations in prescribing of antimicrobials in hospitals and rates of MRSA are analysed in reports on Antimicrobial Use and Resistance in Australia (AURA) Surveillance System data published by the Australian Commission on Safety and Quality in Health Care (ACSQHC). Overall, more than 24% of antimicrobial prescriptions in Australian hospitals were assessed as inappropriate (National Centre for Antimicrobial Stewardship and ACSQHC 2017); methicillin resistance in S. aureus has been stable at around 20% for the last decade, but there is evidence it increased slowly over the three years to 2017, and the rate of community-associated MRSA blood infections is increasing (ACSQHC 2018; Coombs et al. 2018).