Methicillin-resistant Staphylococcus aureus bloodstream infections in the Northern Territory of Australia 2017–2022

Background: Methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infections (BSIs) cause significant morbidity and mortality. In Australia's Northern Territory (NT), MRSA BSI prevalence is disproportionately high. Vancomycin remains standard therapy despite toxicity and complex monitoring requirements. 

Aim: To evaluate demographics, clinical management and outcomes of patients with MRSA BSI in the NT, with a focus on health inequities. 

Methods: This multi-centre retrospective observational study analysed MRSA BSI episodes in hospitalised adults between 2017 and 2022 at the Royal Darwin and Alice Springs Hospitals. Key data were extracted from electronic medical records. Composite treatment failure was defined as follows: outcome of all-cause 90-day mortality, persistent bacteraemia (>7 days) or 90 day relapse. 

Results: Of 182 identified episodes, MRSA accounted for 40% of all S. aureus BSIs. First Nations Australians were disproportionately affected, representing 69% of episodes, with an incidence rate 3.3 times higher than non-Indigenous residents. The composite treatment failure rate was 18%, and 90-day mortality was 13%. Age ≥ 50 years was the only independent variable associated with treatment failure. Notably, 19% of patients required an antimicrobial switch from vancomycin, frequently due to adverse drug reactions. Vancomycin minimum inhibitory concentration (MIC) testing showed high discordance between VITEK2 and E-Test. 

Conclusion: MRSA bloodstream infections remain a significant challenge in the NT, largely due to social and structural factors disproportionately affecting First Nations Australians. While strategies to prevent invasive bloodstream infections should be prioritised, the high incidence of vancomycin-related adverse events and MIC discordance underscores the urgent need for stable, effective oral antimicrobial alternatives and culturally safe, community-led prevention strategies.