The primary objective of this study is to detect differences in anti-S. aureus antibody assays (IgM, IgA, IgG and its subclasses) between (1) a group of patients with bacteremia due to a chronic wound (cases) and (2) a group of patients with localized chronic wound infections (control).

Secondary objectives include:

• To propose a diagnostic marker of bacteraemia based on the detection of anti-S. aureus by xMAP technology
• To evaluate the kinetics of the humoral immune response to S. aureus in patients with bacteraemia
• To evaluate the virulence of S. aureus isolated from chronic, infected wounds
• To enrich the Nîmes University Hospital biobank
• To evaluate the prevalence of different antibodies within each group

Inclusion Criteria:

• The patient must have given his/her informed and signed consent
• The patient must be insured or beneficiary of a health insurance plan
• The patient is available for 6 months of follow up
• Patients consulting at the departments of Diabetology, Dermatology or Infectious Diseases of the participating hospitals
• inaugural or recurrent diabetic foot/ankle ulcers of Grade 2-4, or (2) who have an infected leg ulcer (arterial, venous, or mixed.

Controls:

• Absence of bacteriemia

Cases:

• Presence of bacteriemia

Exclusion Criteria:

• The patient is participating in another study
• The patient is in an exclusion period determined by a previous study
• The patient is under judicial protection, under tutorship or curatorship
• The patient refuses to sign the consent
• It is impossible to correctly inform the patient
• The patient is pregnant, parturient, or breastfeeding
• The patient does not have a chronic wound
• Patient with grand 1 ulcer
• Patient's wound/ulcer is not infected
• Patient's would/ulcer is infected, but not involving S. aureus

Patients consulting at the departments of Diabetology, Dermatology or Infectious Diseases of the participating hospitals and who have (1) inaugural or recurrent diabetic foot/ankle ulcers of Grade 2-4, or (2) who have an infected leg ulcer (arterial, venous, or mixed). This infection must involve S. aureus in a mono-or polymicrobial setting.