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The primary predictor of the etiologic agent for infectious pneumonia is the patient's age, and empiric antibiotic therapy should be based on the most likely etiologic organisms.
Presenting signs and symptoms of pneumonia in infants and children may be nonspecific.
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Pneumonia is an inflammatory process affecting the lung parenchyma and usually is due to an infectious etiology. Physical or chemical agents are noninfectious causes (Table 36-1). Various signs (such as rales) and symptoms (especially cough and fever) may lead to a presumptive “clinical” diagnosis of pneumonia, although pneumonia often is determined by an abnormal chest radiograph. The clinical spectrum of pneumonia is highly variable whether in infants, children, or adults. It ranges from a mild illness to a life-threatening disease with significant morbidity and mortality. Considering the large numbers of microorganisms and other agents that can cause pneumonia, and the limitations of diagnostic testing, the exact cause is often difficult to determine. However, a constellation of clinical, radiologic, and ancillary/laboratory findings may suggest a likely pathogen, and therefore, appropriate therapy (Table 36-2).
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