S. aureus bloodstream infection (SAB) is a severe disease associated with a 30% case-fatality rate at 12 weeks. Severity of this disease is related to the high prevalence of staphylococcal Deep Foci of Infection (SA-DFI), which require prolonged duration of antimicrobial therapy and specific treatment. Timely diagnosis and management of SA-DFI is associated with an improvement of prognosis during SAB. 18 FDG PET/CT (PET/CT) is a useful tool in the diagnosis of infectious foci during bacterial infections.

An ecological study performed in the Netherlands has shown that use of PET/CT in patients with Gram positive cocci bloodstream infection was associated with an increase of detection of DFI and a decrease of recurrences and mortality compared to historical controls.

The investigators hypothesize that SAB poor prognosis is in part related to the lack of diagnosis of all infectious foci and consequently to a suboptimal treatment.

Subjects will be recruited in medical wards of the 10 participating hospitals. Each included patient will be managed according to clinical expertise of investigators who all are experts in the field of infectious diseases. Consensual guidelines for antimicrobial therapy of patients enrolled in the study will be written before the enrolment of the first patient by the steering committee composed of all co-investigators These guidelines will specify the nature of empiric therapy as well as adapted antibiotic therapy for each specific DFI for methicillin-sensitive as well as for methicillin resistant S. aureus.

Experimental group: arm A All patients enrolled in arm A will have a PET/CT after enrolment and not later than day 14 after the drawing of first positive blood culture.

Control group: arm B Patients enrolled in arm B will not have PET/CT before day 14. Other imaging studies will be guided by anamnesis and clinical symptoms and performed according to guidelines written consensually before the enrolment of the first patient by the steering committee

Inclusion Criteria:

• - Aged over 18 years
• Signed informed consent form
• Subjects must be able to attend all scheduled visits and to comply with all trial procedures
• Subjects must be covered by public health insurance
• Hospitalized in one of the 10 participating centres
• At least one peripheral blood culture isolating S. aureus
• Absence of diagnosis of IE according to at least a transthoracic cardiac echography; cardiac echography will be performed via transesophageal procedure if the VIRSTA score is 3 or higher (see Appendix) or if transthoracic echography is not normal.

Exclusion Criteria:

• - Any reason that may compromise compliance with the visit plan
• Planned longer stay outside the region that prevents compliance with the visit plan
• Deprived of liberty subjects (by judicial or administrative decision)
• Adult under guardianshipCatheter-related SAB with resolution of symptoms of infection within 24 hours of ablation of catheter
• Pregnancy or lactation
• Isolation of S. aureus only in blood cultures drawn from a catheter or another implanted device
• Catheter-related SAB with resolution of symptoms of infection within 24 hours of ablation of catheter
• Uncontrolled septic shock and other instability contra-indicating the performance of PET/CT
• Previous performance of PET/CT for the present episode of SAB
• Indication to PET/CT for another reason (eg. neoplasm, infection of vascular graft…)
• Contra-indication to PET/CT
• Contraindication to Fluorodeoxyglucose : hypersensitivity to the active substance or to any of the excipients
• Participation to another study unless specific authorization of the steering committee