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Open Access Research article

Impact of ethnicity and socio-economic status on Staphylococcus aureus bacteremia incidence and mortality: a heavy burden in Indigenous Australians

Steven Y C Tong12*, Sebastian J van Hal34, Lloyd Einsiedel5, Bart J Currie12, John D Turnidge6 and on behalf of the Australian New Zealand Cooperative on Outcomes in Staphylococcal Sepsis

Author Affiliations

1 Tropical and Emerging Infectious Diseases Division, Menzies School of Health Research, Darwin, Northern Territory, Australia

2 Department of Infectious Diseases, Royal Darwin Hospital, Darwin, Northern Territory, Australia

3 Department of Microbiology & Infectious Diseases, Royal Prince Alfred Hospital, Sydney, NSW, Australia

4 Antibiotic Resistance & Mobile Elements Group, Microbiology and Infectious Diseases Unit, School of Medicine, University of Western Sydney, Sydney, Australia

5 Flinders University and the Northern Territory Clinical School, Adelaide, Australia

6 SA Pathology, Women’s and Children’s Hospital, North Adelaide, and University of Adelaide, Adelaide, Australia

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BMC Infectious Diseases 2012, 12:249  doi:10.1186/1471-2334-12-249

Published: 9 October 2012

Abstract

Background

Investigations of the impact of ethnicity and socio-economic status on incidence and outcomes of Staphylococcus aureus bacteraemia are limited.

Methods

We prospectively identified all S. aureus bacteraemia episodes in the Australian New Zealand Cooperative on Outcomes in Staphylococcal Sepsis cohort study between 2007 and 2010. We calculated population level incidence rates using regional postcodes and stratified the analysis by ethnicity, age and socio-economic status indexes.

Results

There were 7539 episodes of S. aureus bacteraemia with an annual incidence of 11·2 episodes per 100,000 population. The age-adjusted incidence in the Indigenous population was 62·5 per 100,000 population with an age standardized incidence rate ratio of 5·9 compared to the non-Indigenous population and an incidence rate ratio of 29.2 for community-associated methicillin-resistant S. aureus (MRSA). Populations in the lowest socio-economic status quintile had an increased S. aureus bacteraemia incidence compared to higher quintiles. However, there was a disparity between Indigenous and non-Indigenous populations across all socio-economic status quintiles. The lower 30-day mortality for Indigenous patients (7%) compared to non-Indigenous patients (17%) was explained by differences in age.

Conclusions

Indigenous Australians suffer from a higher rate of S. aureus bacteraemia than non-Indigenous Australians, particularly for community-associated MRSA. Ethnicity and socio-economic status had little impact on subsequent mortality, with other host factors contributing more significantly.

Keywords:
Staphylococcus aureus; Bacteremia; Ethnicity; Socio-economic status; Indigenous