Atypical pneumonias. Clinical diagnosis and empirical treatment.

Atypical pathogens play an important role in the pathogenesis of community-acquired pneumonias. Early definitive diagnosis is often difficult. Careful attention must be given to the patient's history and other diagnostic clues. When a specific pathogen seems very likely to be the cause, appropriate and cost-effective empirical therapy is best accomplished with a single-drug regimen. However, when typical and atypical pathogens are suspected, combination drug therapy is preferred until the diagnosis is firm and one of the two antibiotics can be dropped.