Reduction the Duration of Antibiotic Therapy in the Elderly (PROPAGE)

Inclusion Criteria: * Age ≥ 80 years * Started antibiotics for a chest infection * Procalcitonin performed J0 antibiotic treatment * Person affiliated to the social security Exclusion Criteria: * Patients with a documented infection with germs after Listeria spp, Legionella pneumophilia, Mycobacterium tuberculosis * Patients with a documented infection with a virus or parasite (eg hemorrhagic fever, malaria) * Patients with endovascular infection associated (endocarditis, pacemaker. Intravascular catheter) * Patients with lung abscess associated upon entry Patients with a chronic infection associated * Patients with severe immunosuppression (HIV or transplant) * Palliative patient * Death within 24 hours of admission to nursing units. * Presence of antibiotic treatment for chronic infection. * Patient under guardianship, curatorship or any other administrative or judicial action or deprivation of the right or freedom * Patients hospitalized without their consent