A. Definition of healthcare-associated Staphylococcus aureus bloodstream infections (SABSI)

A case (or patient episode) of SABSI is defined as a positive blood culture for Staphylococcus aureus. For surveillance purposes, only the first isolate (a culture of microorganisms isolated for study) per patient is counted, unless at least 14 days have passed without a positive blood culture, after which an additional episode is recorded.

A SABSI case is considered to be healthcare-associated if: the first positive blood culture is collected more than 48 hours after hospital admission or fewer than 48 hours after discharge, or if the first positive blood culture is collected 48 hours or less after admission and the patient-episode of SABSI meets at least one of the following key clinical criteria:

  • SABSI is a complication of the presence of an indwelling medical device (for example, intravascular line, haemodialysis vascular access, cerebrospinal fluid shunt, urinary catheter).
  • SABSI occurs within 30 days of a surgical procedure, where the SABSI is related to the surgical site.
  • SABSI was diagnosed within 48 hours of a related invasive instrumentation or incision.
  • SABSI is associated with neutropenia contributed by cytotoxic therapy. Neutropenia is defined as at least two separate calendar days with values of absolute neutrophil count or total white blood cell count (WBC) < 500 cells/mm3 (0.5 × 109/L) on or within a seven-day period which includes the date the positive blood specimen was collected (day 1), the 3 calendar days before and the 3 calendar days after.

The definition of SABSI was developed by the Australian Commission on Safety and Quality in Health Care (ACSQHC). The ACSQHC changed the definition in 2016, with clarification of the neutropenia criterion. The change (which was first applied in the 2015–16 reporting period) is not considered to have resulted in counts of SABSI for 2015–16 that are not comparable with counts for previous years. The definition used for SABSI occurring prior to 1 July 2015 is available at National Healthcare Agreement: PI 22–Healthcare associated infections: Staphylococcus aureus bacteraemia, 2016.

B. NHA PI 22: Healthcare-associated infections

The National Healthcare Agreement performance indicator is calculated using:

  • the number of SABSI patient episodes associated with public hospitals for both hospitals focussing on acute care and hospitals focussing on non-acute or sub-acute care such as psychiatric, rehabilitation and palliative care
  • the number of days of patient care for the public hospitals included in the SABSI surveillance arrangements.

The performance indicator includes data on:

  • counts of SABSI, with data presented separately for MRSA and MSSA SABSI
  • the rate of SABSI per 10,000 days of patient care for public hospitals included in the SABSI surveillance arrangements.

Data are restricted to cases associated with care provided in public hospitals. Cases that are associated with care provided by private hospitals and with non-hospital care are excluded, even if the patients are subsequently treated for the SABSI in a public hospital.

In 2016, the specification of this performance indicator was amended to exclude unqualified days (for example, when acute care was not required) for newborns from the count of days of patient care included in the SABSI surveillance arrangements, which had previously been included.

More information is available from the current specification for this performance indicator, available at National Healthcare Agreement: PI 22–Healthcare associated infections: Staphylococcus aureus bacteraemia, 2021.

C. Data quality statement

  • The NSABDC is a data collection that includes counts of healthcare-associated SABSI for public hospitals covered by SABSI surveillance arrangements, and for private hospitals that choose to provide data. Data collected also includes counts of patient days under surveillance and total patient days.
  • SABSI cases are reported by all states and territories and participating private hospitals using the national agreed case definitions (see Appendix A).
  • There may be imprecise exclusion of some SABSI cases due to the inherent difficulties in determining the origins of SABSI, such as those originating in non-hospital settings.
  • For some states and territories there is less than 100% coverage of public hospitals as surveillance arrangements may not be in place in all wards or all hospitals.
  • The accuracy and comparability of SABSI rates among states and territories and over time are also limited because the count of days of patient care reflects the amount of admitted patient activity.
  • The data for 2011–12 to 2019–20 are comparable. The count of days of patient care reflects the amount of admitted patient activity, but does not reflect the amount of non-admitted patient activity as this cannot be captured due to variations in admission practice.
  • The data for 2010–11 are comparable with subsequent year data except for public hospital data for Queensland.
  • The New South Wales (NSW) Ministry of Health provided the number of occupied bed days for NSW public hospitals rather than the number of patient days under surveillance. The comparability of NSW data and data from other states and territories is therefore limited, but only by the small extent that counts of occupied bed days would be expected to differ from counts of days of patient care.
  • The 2019–20 patient day and coverage data may be preliminary for some hospitals or states and territories.
  • Private hospitals supply data voluntarily to the NSABDC, and not all private hospitals report data. The casemix of patients treated in private hospitals may also be different to that in public hospitals. Coverage of the private sector is therefore incomplete and reported data may not be representative of the sector as a whole.
  • Due to the changes in 2016 to the denominator of the performance indicator specification, data published in 2017 and subsequent years for the reporting years 2010–11 to 2014–15 are not comparable with data previously published in:
    • the Council of Australian Governments (COAG) Reform Council publications
    • the AIHW series ‘Staphylococcus aureus bacteraemia in Australian public hospitals: Australian hospital statistics’
    • the annual Report on Government Services produced by the Steering Committee for the Review of Government Service Provision.

For the full data quality statement see Data quality statement for the 2019–20 NSABDC