This study looks at how well one antibiotic (monotherapy) works compared to two antibiotics (combination therapy) in treating bone infections caused by Pseudomonas aeruginosa. It includes 300 adult patients who had this type of infection confirmed by lab tests and medical imaging. The goal is to find out if using just one antibiotic is as effective as using two, while also looking at side effects, the need for more surgery, antibiotic resistance, and overall antibiotic use.

Inclusion Criteria:

• Adult patients (≥18 years old)
• Diagnosis of osteitis or osteomyelitis due to Pseudomonas aeruginosa
• Isolation of Pseudomonas aeruginosa from at least one deep, sterile sample (e.g., bone biopsy, joint aspiration)
• Imaging findings consistent with osteomyelitis (MRI, CT scan, or X-ray)

Exclusion Criteria:

• No isolation of Pseudomonas aeruginosa
• No imaging evidence suggestive of osteomyelitis
• Patients under 18 years of age

Participants will be selected from the electronic health records of adult patients hospitalized within the AP-HP (Assistance Publique-Hôpitaux de Paris) network. The study population includes individuals diagnosed with osteitis or osteomyelitis who have a confirmed microbiological diagnosis of Pseudomonas aeruginosa infection, along with imaging consistent with bone infection.