Antimicrobial Treatment in Patients With Ventilator-associated Tracheobronchitis

The main objective of this randomized controlled multicenter double-blind trial is to assess the efficiency of two durations (3 or 7 days) of antibiotic treatment for VAT, compared with no antibiotic treatment, in reducing the incidence of transition from VAT to ventilator-associated pneumonia (VAP). Secondary objectives are to determine the impact of two durations (3 or 7 days) of antibiotic treatment for VAT, compared with no antibiotic treatment, on: * duration of mechanical-ventilation free days * duration of antibiotic free days * length of ICU stay * mortality at day 28 and day 90 * incidence of ICU-acquired colonization related to multidrug resistant (MDR) bacteria * incidence of ICU-acquired infection related to MDR bacteria * incidence of ventilator-associated events After informed consent, patients will be randomized (1:1:1) to receive 0 (control group), 3 or 7 days (experimental groups) of antibiotic treatment for VAT Antibiotic treatment is standardized, based on the time of onset of VAT, and presence of risk factors for MDR bacteria: * patients with early-onset VAT with no risk factor for MDR bacteria will receive ceftriaxone (2 g iv every 24h). * patients with late-onset VAT (after day 4 of mechanical ventilation), or with at least one risk factor for MDR bacteria will receive imipenem (1 g iv every 8h), and ciprofloxacin (400 mg iv every 8h) as empirical treatment. When methicillin-resistant Staphylococcus aureus is suspected, linezolid (600 mg iv every 12h) will be added to empirical treatment. Patients randomized in control group will receive 7 days of placebo, and those randomized in the first experimental arm (3 days of antibiotics) will receive 4 days of placebo.