A case (or patient episode) of SAB 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 SAB 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 SAB meets at least one of the following key clinical criteria:
- SAB is a complication of the presence of an indwelling medical device (for example, intravascular line, haemodialysis vascular access, cerebrospinal fluid shunt, urinary catheter).
- SAB occurs within 30 days of a surgical procedure, where the SAB is related to the surgical site.
- SAB was diagnosed within 48 hours of a related invasive instrumentation or incision.
- SAB 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 SAB 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 SAB cases for 2015–16 that are not comparable with counts for previous years. The definition used for SAB cases occurring prior to 1 July 2015 is available at National Healthcare Agreement: PI 22–Healthcare associated infections: Staphylococcus aureus bacteraemia, 2016.