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Hospital Performance: Healthcare-associated Staphylococcus aureus bloodstream infections in 2011–12

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About this report

This report examines the number of bloodstream infections caused by a specific organism, called Staphylococcus aureus (S. aureus), that were acquired while patients were receiving medical care or treatment in hospital.

It compares the performance of 352 hospitals across Australia against their peers, after grouping them into categories based on size and proportion of vulnerable patients.

The National Health Performance Authority bases its performance reports on indicators agreed by the Council of Australian Governments. In this report, the Authority has focused on one of these indicators that refers to rates of healthcare-associated S. aureus bloodstream infection.

The national benchmark specified in the National Healthcare Agreement1 is that the rate of S. aureus bloodstream infection in each state or territory should be no more than 2.0 cases per 10,000 patient bed days.

The report names some hospitals that have reported higher and lower rates of healthcare-associated S. aureus bloodstream infection than their peers. However, uncertainties about the completeness and national consistency of data across all hospitals are such that it is not possible to draw definitive conclusions about hospital performance. As a result, the Authority makes no determination in this report that any hospitals are good or bad performers.

Instead, the information in this report is intended to provide the public, clinicians and public hospital managers with a greater insight into how hospitals are performing against similar hospitals, and to inform efforts to improve care.

It is also intended that the report will demonstrate what could be possible with more detailed and nationally consistent data, and will help stimulate improvements to collection of data for national reporting.

What is healthcare-associated Staphylococcus aureus bloodstream infection?

Staphylococcus aureus (S. aureus) is a bacterium frequently found in the airways, lungs and skin of healthy people. S. aureus can cause significant illness when it results in an infection in the bloodstream. Doctors call this ‘Staphylococcus aureus bacteraemia’ (or bloodstream infection).

The term ‘healthcare-associated’ means that the infection was acquired during interaction with healthcare services. This report focuses on healthcare-associated S. aureus bloodstream infections attributable to Australian public hospitals.

Patients in hospital are vulnerable to S. aureus bloodstream infection because wounds, surgery and other medically invasive procedures can provide an opening through our protective skin layers and allow organisms into our body. In addition, some people in hospital are more vulnerable than other patients to such infections, for example, patients with weakened immune systems.

Infections acquired in hospital can mostly be prevented through simple hygiene practices. After infections have developed, they can be mitigated by early detection and effective treatment strategies.

Patients with healthcare-associated S. aureus bloodstream infection can become very ill and have longer stays in hospital. Such infections can be very serious: evidence from Australia suggests between 20% to 35% of people who experience S. aureus bloodstream infection die from this or a related cause.2,3,4

About the data

S. aureus cases are identified when a medical professional notices the symptoms of infection and orders a blood test. If this blood test identifies infection by S. aureus, the infection control officer for the hospital is notified. These experts judge if the infection is healthcare-associated and, if so, attribute it to the appropriate hospital.

Many steps are necessary for a case of healthcare-associated S. aureus bloodstream infection to be recorded. Failure to take any of these steps can interrupt this sequence and lead to under-reporting of this infection.

This report is based on data from 352 hospitals across Australia that monitored S. aureus bloodstream infection and had more than 5,000 patient bed days monitored. These 352 hospitals accounted for over 97% of all monitored bed-days in 2011–12, and over 99% (1725 of 1734) of all reported cases.

Data for this report were provided by states and territories to the National Staphylococcus aureus Bacteraemia Data Collection and the Admitted Patient Care National Minimum Data Set, both from 2011–12.

Fair comparisons: hospital peer groups

Direct comparisons between all hospitals is not necessarily fair due to the fact that some hospitals deal with more of the types of patients most at risk of these infections.

To address this, and to allow fairer comparisons, the Authority has allocated hospitals to one of eight groups based on a combination of size of hospital, type of services provided and the percentage of patients more at risk of healthcare-associated infection.

Vulnerable patients

For the purposes of this report, patients are considered ‘vulnerable’ if they have one or more of the following risk factors:

1. Immunosuppressed patients.

Such as patients admitted for:

  • Bone marrow transplant
  • Burns
  • Disorders of the immune system
  • Oncology, including haematological malignancy
  • Transplant


2. Opportunities for infection.

Such as patients admitted for:

  • Acute renal failure
  • Acute spinal injury
  • Surgery (including cardiac surgery)
  • Venous catheterisation.

Appendix table 1 describes the peer group classification for hospitals. In addition to these eight peer groups, two further groups of hospitals were not similar enough to other hospitals or to each other to be compared: specialist women’s and children’s hospitals, and ‘other’ hospitals. For more information see Hospital Performance: Healthcare-associated Staphylococcus aureus bloodstream infections in 2011–12, Technical Supplement.

Hospitals in the same peer group are more similar to each other than to hospitals in other peer groups in terms of the hospital size and number of patients with weakened immune systems.

While the Authority has reported details on healthcare-associated S. aureus bloodstream infections in more than 600 hospitals on its website, a cautious approach has been taken to comparing performance by only naming the 10% of hospitals in the two major hospitals peer groups that reported the highest rates, as well as the 10% that reported the lowest rates. There are two reasons for this:

  1. While the national definition for healthcare-associated S. aureus bloodstream infection was endorsed by states and territories in 20095, the definition for national submission of data has evolved and changed more than once since then to allow it to be used for public reporting.

    While the data in this report is for the period 2011–12, information reviewed by the Authority demonstrated differences in how states and hospitals measure and record cases and patient bed days. This suggests it is too early to expect national consistency in comparing hospitals across Australia.

  2. While there are many hospitals reporting cases, a culture of disclosure is still relatively new. By reporting on the occurrence of these events we can best identify where actions are most needed.

Improving comparisons

In its work to better understand the data available for reporting healthcare-associated S. aureus bloodstream infections, the Authority identified opportunities to improve information to compare hospitals.

The Authority undertook to risk-adjust rates of S. aureus bloodstream infection but, following analysis and consultation, concluded that the information systems are not mature enough to support this approach. Work will continue to further develop approaches to support fair comparisons between hospitals.

The extent to which a hospital is monitored by infection control staff varies between states and between hospitals within each state. Most hospitals (94%) report complete coverage by infection control monitoring systems of all patient bed days. While monitoring systems are maturing, there remain some hospitals that have partial coverage (Figure 1a and Figure 1b).

See Hospital Performance: Healthcare-associated Staphylococcus aureus bloodstream infections in 2011–12, Technical Supplement for more details.

Council of Australian Governments, 2011. National Healthcare Agreement. [Online] Available at: Accessed 28 April 2013.
Collignon PJ, Wilkinson IJ et al. Health care-associated Staphylococcus aureus bloodstream infections: a clinical quality indicator for all hospitals. Med J Aust 2006;184(8):404–406.
Turnidge JD, Kotsanas D et al. Staphylococcus aureus bacteraemia: a major cause of mortality in Australia and New Zealand. Med J Aust 2009;191(7):368–373.
Van Hal SJ, Jensen SO et al. Predictors of Mortality in Staphylococcus aureus Bacteremia. Clin Microbiol Rev 2012:25(2):362–386.
Australian Commission on Quality and Safety in Health Care. Implementation guide for the surveillance of Staphylococcus aureus bacteraemia. Sydney:ACQSHC, 2011.
Download Report (PDF, 467.7 KB)