Inclusion Criteria:  Under mechanical ventilation from more than 48 hours Suspected for a ventilator acquired pneumonia, requiring a distal pulmonary bacterial sample  Exclusion Criteria:  New or worsening shock requiring vasopressor New or worsening severe hypoxemia (PaO2/FiO2<150 in FiO2≥60% and peep 10) Patient under veno-veinous extracorporeal membrane oxygenation Neutropenia <1G/L or immunosuppressive treatment (including corticosteroids >6 months or >0.5mg/kg/j) Disease (endocarditis, spondylodyscitis, deep abcedation…) requiring prolonged antibiotic therapy