It exists recommendations to get an optimal antibiotic treatment for bone and joint infection and prescription of antibiotics in the bone and joint infections on material meets certain obligations: the micro-organism must be known, the antibiotic therapy must be started in association, obtaining high plasma levels, use of molecules having good bone circulation. It is recommended to initially administer treatment with intravenous route and to propose an oral relay, under conditions. It is recommended to administer the antibiotic treatment for at least 6 weeks.

The dosages of antibiotics are adapted to the weight of patients in order to respond to those recommendations. But little is known about the optimal dose of treatment to give to obese patients (BMI>=30) and the frequency of serious adverse events in these patients in which the dosage is then higher can be more important compared to non-obese patients. The aim of the study is then to evaluate the risk of occurrence of serious adverse events in obese patients and to identify risks factors.

This study consists in a retrospective cohort of obese patients treated for a bone or joint infection and having had a serious adverse event. Several data are collected concerning: demographics data, treatment responsible of the serious adverse event (molecules, dosage, route), description of the serious adverse event, residual rate for vancomycin.

Inclusion Criteria:

• patients (i.e age ≥ 15 year-old) with bone and joint infection
• with or without implant
• for which the BMI is >=30
• having had a serious adverse event related to the antibiotic treatment.

Exclusion Criteria:

• none

Obese patients, under antibiotic treatement for bone or joint infection and who presented a serious adverse event