Staphylococcus aureus nasal carriage is a well-known risk factor for S. aureus surgical site infections (SSI). According to a recent study demonstrating 60% reduction risk of SSI due this bacterium after patients' screening and decolonization, recent French and WHO guidelines recommend in cardiac surgery the decolonization of nasal S. aureus carriers before surgery. In practice the decolonization procedures are not well-defined according notably to the duration and time of delivery before surgery and doses of topical antimicrobial drugs. The aim of the proposed study is to investigate the factors associated with failures of S. aureus decolonization: carriage state, compliance with treatment, S. aureus capacity of internalization in nasal epithelial cells, resistance to antimicrobial drugs used. This study will allow (i) to measure the frequency of patients with residual S. aureus carriage just before surgery, whatever they have been decolonized or not, (ii) to characterize the S. aureus nasal carriage state of patients before surgery, and (iii) to investigate the adding value of mupirocin dosage in the nose and urines of decolonized patients as a marker of compliance and efficacy of the decolonization process.

Inclusion Criteria:

• Patient to benefit from cardiac surgery scheduled at Saint-Etienne University Hospital
• Surgery of first intention (no resumption)
• Patient affiliated or entitled to a social security scheme
• Patient agreeing to participate in the study and having signed the informed consent

Exclusion Criteria:

• Surgery in a context of infection
• Surgery in an emergency and semi-emergency context
• Protected major patient
• Pregnant

The study will be offered to all major patient who needs cardiac surgery