Patients will continue their existing aspirin.

Death from any cause

Defined as change in therapy for inadequate clinical response; new endocarditis; new evidence of other deep metastatic foci (e.g., osteomyelitis or deep abscess); relapse of MRSA bacteremia after a patient has sterilized their initial blood cultures; readmission for subsequent care of S. aureus bacteremia; need for unplanned source control procedures. New implies that the complication was not suspected at enrollment and is not a function of delay to diagnostic testing.

This will be defined according to the criteria of the International Society on Thrombosis and Haemostasis as one or more of the following: fatal bleeding; symptomatic bleeding in a critical area or organ (including hemorrhagic stroke); bleeding that causes a fall in hemoglobin level of ≥20 g/L; or bleeding that requires a transfusion of 2 or more units of whole blood or red cells. For bleeds into non-critical areas, we will also record the site of bleeding.

This will be defined as an acute objectively confirmed deep vein thrombosis (upper extremity, lower extremity, other such as portal vein, cerebral vein, splanchnic vein) and/or segment or proximal pulmonary embolism, which is symptomatic and/or necessitates specific treatment. Below knee DVT and superficial thrombophlebitis are not included. Pulmonary embolism needs to be, segmental or proximal. Subsegmental pulmonary embolisms are not included as they have poor interrater reliability and may represent artefact in up to 50% of cases.

Stroke is defined as the acute onset of focal neurological dysfunction caused by brain, spinal cord, or retinal vascular injury because of infarction (ischemia). Ideally, at least one of the following should be present to confirm the diagnosis of stroke: confirmation by neurology, stroke specialist, or neurosurgical specialist, brain imaging (e.g., CT scan, MRI scan, or cerebral vessel angiography compatible with acute ischemia). If the acute focal signs represent a worsening of a previous deficit, these signs must persist for more than 24 hours and be accompanied by an appropriate new MRI or CT scan finding. In the absence of neuroimaging, a staff neurologist consult which makes the diagnosis of stroke will be considered.

Patients with S. aureus bacteremia often have substantial physiological stresses which can be associated with rises in cardiac troponin (demand ischemia). For the purposes of this outcome, acute myocardial infarction is captured as a type 1 myocardial infarction: detection of rise and/or fall of cardiac biomarkers with at least one value above the 99th percentile of the upper reference limit together with evidence of myocardial ischemia. For the purposes of this pragmatic trial, such a myocardial infarction will be inferred from the opinions of the staff cardiologist, intensivist, or general internal medicine specialist. The peak troponin value will be recorded, and a redacted copy of the relevant consultant's note and ECGs will be uploaded for audit.

Clinical history compatible with sudden worsening of end organ or limb perfusion and confirmation by imaging (e.g., CT angiography, arterial doppler) or need for urgent surgery or thrombolysis.