Initial investigation and treatment of the patient with severe community-acquired pneumonia.

Approximately 5% to 10% of patients hospitalized with community-acquired pneumonia (CAP) require treatment in an intensive care unit (ICU) because of severe disease. The case fatality rates in these patients are high, between 20% and 50% in most series. Streptococcus pneumoniae, Legionella spp, Haemophilus influenzae, Staphylococcus aureus, and gram-negative enteric bacteria are the most common causes of severe CAP. However, because the spectrum of pathogens encountered in these patients is unlimited, including viruses, tuberculosis, and opportunistic pathogens, it is crucial to obtain an etiologic diagnosis. A complete diagnostic arsenal should be used, including, if possible, invasive diagnostic procedures before antibiotics are given. The initial empirical therapy must cover the most common pathogens, and in most patients this can be accomplished with a combination of a cephalosporin and a macrolide.