The presence of S aureus in the nasal passages of diabetic patients may be a risk factor for diabetic foot lesion infections. Our aim is to compare the genetic profiles of S aureus strains found in the noses and on the foot lesions of diabetic patients. The investigators are also studying the virulence of these strains, the prevalance of S aureus at either site, and whether or not the quantity of S aureus found in the nose affects the risk for infection in foot lesions. The investigators also use this study to test the sensitivity and specificity of the GeneXpert system.

Inclusion Criteria:

• Type 1 or 2 diabetic patients
• Patients consulting or hospitalized in the Diabetology departments of one of the participating centers
• Grade 2-4 ulcer on the foot or ankle (both primo and recurrent events are acceptable)

Exclusion Criteria:

• Patient refuses to participate
• Pregnant, parturient or breastfeeding women
• Patient does not have diabetic foot or arteritic
• Diabetic ulcer is located elsewhere than the foot or ankle
• The ulcer is non-swabbable
• Patient does not have social-security coverage
• Patient is under any type of guardianship

Adult type 1 or 2 diabetic patients with grade 2-4 foot or ankle ulcers (first event or recurrence)