The main objective of this study is to characterize the evolution (over a period of 28 days) of superficial and deep bacterial skin flora in patients with stage 3 or 4 sacral pressure ulcers (bedsores). Changes in terms of pathogenic, potentially pathogenic and non-pathogenic bacterial species at the intra-individual and population levels.

The secondary objectives of this study are:

A. To compare bacterial communities collected from superficial versus deep samples of stage 3 or 4 sacral bedsores using metagenomics and standard culturing methods.

B. To characterize the evolution of digestive bacterial flora in the same patients over a period of 28 days. Changes in terms of pathogenic, potentially pathogenic and non-pathogenic will be described, as well as the appearance of resistance phenotypes.

C. To characterize the evolution of urinary bacterial flora in the same patients over a period of 28 days. Changes in terms of pathogenic, potentially pathogenic and non-pathogenic will be described, as well as the appearance of resistance phenotypes.

Inclusion Criteria:

• The patient was correctly informed about study implementation, its objectives, constraints and patient rights
• 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 28 days of follow-up
• The patient has one or more pelvic pressure ulcers (bedsores)(stage 3 or 4 only). Note: Patients with bedsores of varying stage will be included for the wound corresponding to the highest stage. If the patient has multiple bedsores of the same stage, the deepest wound will be selected.
• The patient requires a modern wound dressings (i.e. not tulle or gauze) without added bactericidal or antibiotic elements
• The patient is hospitalized ant the Propara neurological rehabilitation center (Montpellier, France)
• The patient has not received antibiotics in the last 14 days.

Exclusion Criteria:

• The patient is participating in another study, or has participated in another study in the last 3 months
• 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 is already included in the present study
• The patient has sacral pressure ulcers of only stages 1 or 2, or does not have a sacral pressure ulcer
• Patient under curative anticoagulation
• Patient who received antibiotics within 14 days before inclusion (however, after inclusion, the patient can be treated with antibiotics if necessary)

The study population consists of patients hospitalized in the Propara neurological rehabilitation (Montpellier, France) having at least one stage 3 or 4 bedsore in the pelvic region.