Streptococcus pneumoniae is a Gram-positive diplococcus with a well-formed capsule. This organism is one of the commonest seen in community-acquired pneumonias, accounting for up to 25% of these infections. In the preantibiotic era streptococcal pneumonia or pneumococcal pneumonia had a high fatality rate, being a frequent cause of death in the elderly.
Today certain serotypes of S. pneumoniae will rarely produce necrotizing abscesses in the lung. Usually, however, pneumococcal pneumonia presents as homogeneous air space consolidation occupying a portion of a segment or lobe of lung particularly in the periphery. Air bronchograms are frequently identified as evidence of parapneumonic effusion (Fig.1). Both single and multiple lobes may be involved. Radiographic evidence of resolution is generally identified within a few days of appropriate antibiotic therapy.
Complete resolution of the pneumonia, however, may be delayed for several weeks. Clinically patients present with high fever, chills, productive cough, and occasionally pleuritic pain. In patients with a healthy immune system the prognosis with appropriate antibiotic therapy is very good. However, in patients with a failure to develop leukocytosis the mortality rate is very high.
Imaging Examples
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Streptococcus pneumonia, Fig.1 | |
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