Treatment of community-acquired pneumonias.

Community-acquired pneumonia resulting in hospitalization may have a mortality rate of 10 to 25 percent. The exact incidence of community-acquired pneumonia is unknown because it is not a reportable disease. The etiologic spectrum appears to be changing. Streptococcus pneumoniae causes most of the cases; the rank ordering of other pathogens is uncertain. With the exception of Legionella, colonization of the upper respiratory tract usually precedes clinical pneumonia. Subtle aspiration of the posterior pharyngeal flora accounts for the majority of pneumonias. The need for prompt antibiotic therapy mandates an efficient approach to diagnosis, although it is often difficult to establish a precise etiology. Empiric therapy is often initiated prior to an etiologic diagnosis, and should be as specific as possible. Initial choice of therapy is dictated by the clinical presentation (e.g., "bacterial-like" or "viral-like"), inquiries into the possibility of aspiration or gram-negative pneumonia, and the results of gram-stain examination. When the clinical presentation and Gram-stain results are consistent with pneumococcal pneumonia, penicillin is the drug of choice. A more obtuse presentation in an otherwise healthy patient may call for erythromycin to cover Legionella and Mycoplasma. "Marginally compromised" hosts, such as alcoholics, patients with chronic obstructive pulmonary disease, and elderly nursing home patients, may require empiric broad-spectrum cephalosporin therapy for the first few days. Prevention of pneumonia using available vaccines must be emphasized.