Staphylococcus aureus bacteraemia at Alice Springs Hospital, Central Australia, 2003-2006

Background: Infectious diseases remain the leading cause of death at Alice Springs Hospital (ASH) and Staphylococcus aureus bacteraemia (SAB) is the second most common bloodstream infection. Non-multidrug-resistant, methicillin-resistant S. aureus (nmMRSA) is endemic to the region. Aims: To determine whether differences exist between racial groups and resistance phenotypes in the clinical manifestations and outcomes of SAB at ASH. Methods: A retrospective review of medical and pathology records for inpatients with SAB between 1 January 2003 and 31 December 2006. Results: A total of 125 patients (indigenous, 111; non-indigenous, 14) presented with SAB during the study period. Among indigenous patients, there were 95 adults and 16 children. No non-indigenous child was admitted with SAB. The mean annual incidence rate was 160.7/100000 indigenous population and 8.1/100000 non-indigenous population (incidence rate ratio 19.9) (P=0.010). Isolates were predominantly methicillin-susceptible S. aureus (indigenous, 85; non-indigenous, 13). Twenty of 27 MRSA isolates were non-multidrug-resistant. Indigenous adults were more likely to present with an infective focus (indigenous, 75; non-indigenous, 6) (P=0.004). These were most often skin infections (skin abscesses, 31; scabies, 4). Twenty-seven indigenous adults self-discharged after receiving a median of only 5days (inter-quartile range (IQR), 3-9) of antibiotic therapy. Ninety-day mortality rates for indigenous and non-indigenous adults were 14.7% and 14.3% respectively. The median age of death for indigenous adults was 50years (IQR, 37-68). Conclusions: Indigenous Australians have the highest reported incidence rate of SAB worldwide. This reflects the socioeconomic disadvantage experienced by indigenous Australians whose living conditions predispose to pathogen transmission and limits opportunities to maintain adequate skin hygiene.