Clindamycin and rifampicin are authorized in osteoarticular infection treatment (IDSA guidelines) but some interaction is observed. The objective of this study is to evaluate and quantify rifampicin interaction on clindamycin

It could suggest modification of recommended doses or incitement to antibiotic dosage. Thus, theses antibiotics, if association is allowed, could limit fluoroquinolones prescription and avoid some antibiotic resistance.

Inclusion Criteria:

• patients ≥18 years of age
• osteoarticular infection
• staphylococcus detected in bacteriological sampling
• sensibility to rifampicin, erythromycin and clindamycin
• active intravenous antibiotherapy against staphylococcus detected in bacteriological sampling

Exclusion Criteria:

• septic shock or severe initial sepsis
• osteoarticular infection with other microorganism than staphylococcus
• contraindication to clindamycin or rifampicin including case of hypersensibility to one of these two antibiotics
• pre-existing renal insufficiency or severe renal insufficiency (creatinine clearance <30 ml/min)
• serious cognitive disorders
• patient under guardianship, trusteeship or non affiliated to social security or CMU (beneficiary or assignee)
• refusal to take part in the study and to sign the consent form
• pregnancy
• lactation
• administration of clindamycin or rifampicin within the month before inclusion
• treatment with enzymatic inductor or inhibitor within the month before inclusion
• participation to another study modifying antibiotic treatment administration