The epidemiology of Staphylococcus aureus bacteraemia in Tasmania

Abstract. Background: The seriousness of Staphylococcus aureus bacteraemia (SAB), coupled with the potential to reduce its occurrence, suggests that each case of SAB demands rigorous investigation and epidemiological understanding. To accurately determine the incidence and better understand the epidemiology of SAB at a population level, detailed data about SAB need to be collected from all settings, not just publicly funded hospitals. The aim of this study was to understand the epidemiology of SAB in Tasmania and to quantify the extent to which SAB incidence is under reported if only public hospital data are reported. Methods: A population-based observational study for all people who had laboratory-identified SAB during 2009 and 2010 in Tasmania was conducted. The incidence of SAB was calculated using population data. Results: Incidence of SAB was calculated as 21.3 per 100 000 population per year (95% CI 18.51–24.31). The majority of SAB cases were community associated (58.4%) and were caused by methicillin-sensitive Staphylococcus aureus (90.7%). Fifty-five percent of healthcare-associated SAB cases were associated with an intravascular device. Eleven percent of all SAB cases were identified in a private hospital. Conclusion: This study represents the first known Australian study to capture and analyse data from all cases of SAB in a well-defined population, enabling calculation of incidence. The incidence of SAB in Tasmania is lower than in other Australian studies. Community-associated SAB is more common than healthcare-associated SAB yet little attention is paid to this community burden nationally. Current national surveillance programs for SAB focus only on public hospitals and, in doing so, a significant number of cases of SAB are missed.