Main objective- To study the influence of the polymorphisms of nuclear receptor proteins pregnane X receptor (PXR), Liver X receptor alpha (LXRα), and Cytochrome P450 (CYP450) on the clindamycin clearance during clindamycin/rifampin combination therapy.

Secondary objectives To study the influence of these polymorphisms on clindamycin clearance, before combination therapy with rifampin (clindamycin monotherapy) To study the influence of these polymorphisms on CYP450 activity before combination therapy with rifampin (clindamycin monotherapy) To study the influence of these polymorphisms on the increase of CYP450 activity after clindamycin/rifampin combination therapy To study the difference between the expected and observed clindamycin serum concentrations after dosage adjustment, in patients with clindamycin dosage adjustment after combination therapy with rifampin

Eligible patients will be informed on the study during their hospitalisation in the unit for the treatment of bone and joint infection by the medical doctor. If they agree to participate in the study, the following samples will be performed :

• After at least 24 hours of clindamycin therapy and before combination therapy with rifampin:

  • 1 urine sample (5 mL) for CYP 450 activity phenotyping
  • 1 blood sample (5 mL on ethylenediaminetetraacetic acid (EDTA) tubes) for measuring clindamycin serum concentration and genotyping

• After ten days of clindamycin-rifampin combination therapy:

  • 1 urine sample (5 mL) for CYP 450 activity phenotyping
  • 1 blood sample (5 mL on EDTA tubes) for measuring clindamycin serum concentration and genotyping

Inclusion Criteria:

• bone or joint infection
• aged ≥ 18 years old
• treatment with clindamycin/rifampin combination therapy > 10 days

Exclusion Criteria:

• prescription of another treatment with potential action on CYP450
• pregnant or breast feeding patient

patient treated for a bone or joint infection with a clindamycin/rifampin combination therapy, for at least 10 days