Inclusion Criteria:  Admitted to the ICU within the last 24 hours, or with a witnessed aspiration event in the last 24 hours while in the ICU Radiographic findings on chest x-ray or CT deemed by the treating ICU team to be consistent with aspiration (e.g. dependent infiltrates or intraluminal airway debris) Clinical history consistent with possible aspiration (e.g. cardiac arrest, found unconscious, or with a witnessed aspiration event).  Exclusion Criteria:  Already received 3 or more doses of any antibiotic since hospital presentation, unless the last dose was greater than 1 week before enrollment Requires antibiotic therapy for the treatment of other infections Patient "comfort measures only" at time of screening Currently participating in other trials using investigational drugs or interventions Currently pregnant Currently a prisoner The consenting party (patient or their legally authorized representative) is unable to understand or read English at a fifth-grade level. 2 or more of the following are present at the time of screening: White blood cell count: ≥ 11.0 Temperature ≥ 38.0C (100.4F) Purulent secretions S/F (pulse oximetry saturation to FiO2) ratio ≤ 215