Not "a cute" complication: phenotypic analysis of acute kidney injury in S. aureus bacteraemia.

Objectives: In this large retrospective cohort analysis, we aimed to determine the incidence of KDIGO-defined acute kidney injury (AKI) within 14 days in patients with Staphylococcus aureus bacteraemia, and the association of AKI with 30-day mortality.

Methods: A retrospective cohort study of adults with S. aureus bacteraemia between 1998 to 2023 admitted to a large regional Australian health service. Baseline creatinine was the lowest serum creatinine concentration in the 365 days before the day of index blood culture collection and AKI was defined and staged using KGIDO criteria. AKI were classified as early (within 48 hours of index blood culture) or late (48 hours to 14 days after index blood culture).

Results: In those with S. aureus bacteraemia (SAB), AKI occurred in 46% (1255/2734) and was significantly linked to all-cause 30-day mortality (for patients with AKI, 354 died, 901 survived, without AKI 138 died and 1341 survived; OR 3.81 95% CI 3.08 to 4.73, p=<0.001). Overall 30-day mortality was 18% (492/2734). AKI resolution within 14 days occurred in 173/277 (62%) of those with an early AKI only, and 101/435 (23%) of those with a late AKI only (p=<0.001).

Conclusions: AKI is a frequent complication of S. aureus bacteraemia and is associated with 30-day mortality. Some AKI phenotypes have rapid resolution, which supports consideration of delayed antimicrobial dose reduction.