Within 48 hours of enrolment, we sought to establish a diagnosis of pneumonia through culture and susceptibility testing of respiratory secretions obtained by deep expectoration, nasotracheal aspiration, intubation with endotracheal suctioning, bronchoscopy with BAL or protected-brush sampling, or transtracheal aspiration. The diagnosis could also be supported by culture of samples obtained by percutaneous lung or pleural fluid aspiration, and/or single diagnostic antibody titer, (IgM), or a four-fold increase in paired serum samples (IgG) for the presumed pathogen. Patients with burns greater than 20% of total body surface, expected death within 48 h, post bone marrow transplant within the last 6 months, cardiogenic shock, cardiovascular bypass within the last 7 days, solid organ transplant within the last 14 days, or patients participating in other studies were excluded.