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Background: The Central Australian Indigenous population has a high incidence of Staphylococcus aureus bacteremia (SAB) but little is known about the local molecular epidemiology., Methods: Prospective observational study of bacteremic and nasal colonizing S.aureus isolates between June 2006 to June 2010. All isolates underwent single nucleotide polymorphism (SNP) genotyping and testing for the presence of the Panton-Valentine Leucocidin (pvl) gene., Results: Invasive isolates (n = 97) were predominantly ST93 (26.6 %) and pvl positive (54.3 %), which was associated with skin and soft tissue infections (OR 4.35, 95 % CI 1.16, 16.31). Non-multiresistant MRSA accounted for 31.9 % of bacteremic samples and showed a trend to being healthcare associated (OR 2.16, 95 % CI 0.86, 5.40). Non-invasive isolates (n = 54) were rarely ST93 (1.9 %) or pvl positive (7.4 %)., Conclusions: In Central Australia, ST93 was the dominant S.aureus clone, and was frequently pvl positive and associated with an aggressive clinical phenotype. Whether non-nasal carriage is more important with invasive clones or whether colonization occurs only transiently remains to be elucidated.

Background: An association between blood stream infections (BSI) and HTLV-1 seropositivity in Indigenous Australians might result from HTLV-1 mediated inflammation and parasite coinfections that provide portals of entry for bacteria., Objectives: To determine whether BSI risk increases with HTLV-1c proviral load (PVL) and to identify the pathogens responsible in the context of HTLV-1 related conditions., Study Design: Indigenous adults admitted to Alice Springs Hospital, central Australia, were recruited as cases or controls according to whether they had a BSI. Clinical data were extracted from case notes and the hospital pathology database. HTLV-1 serology and PVL assays were then performed and risk factors for BSI were determined for HTLV-1 infected subjects., Results: Risk factors were compared between 44 cases and 30 controls who were HTLV-1 Western blot positive. In a multivariable model, high HTLV-1c PVL was predictive of BSI during the study period (OR, 9.10; 95% CI, 2.40-34.4). Median (IQR) HTLV-1c PVL (copies per 100 PBL) was 39-fold higher for patients recording any BSI (0.116 (0.009, 0.277)) relative to those who had no BSI (0.003 (0.000, 0.067))(p=0.0007). Mean (SD) PVL for subjects with no BSI (n=27), 1 BSI (n=37) and ≥2 BSI (n=10) during the study period were 0.120 (0.301), 0.271 (0.622) and 0.500 (0.654) copies per 100 PBL, respectively (p=0.0007). Five BSI were associated with possible complications of HTLV-1; strongyloidiasis (3), infective dermatitis (1), HTLV-1 associated bronchiectasis (1)., Conclusions: Higher HTLV-1c PVL predicts BSI risk; however; most BSI were not associated with recognised complications of HTLV-1 infection., (Crown Copyright © 2016. Published by Elsevier B.V. All rights reserved.)

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.

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 160.7/100 000 indigenous population and 8.1/100 000 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 5 days (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 50 years (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., (© 2011 The Authors. Internal Medicine Journal © 2011 Royal Australasian College of Physicians.)