A Pathogenetic Categorization of Clinical Syndromes Caused by Streptococcus pneumoniae

Abstract

This chapter discusses clinical syndromes caused by Streptococcus pneumoniae, categorizing them based on pathogenesis and immune response. The current understanding of hematogenous infection is based on an expanded understanding of events in which pneumococci “settle out in” or “seed” various body sites. The resulting infections include meningitis, primary peritonitis, septic arthritis, osteomyelitis, and soft tissue infection. Important in the pathogenesis of acute sinusitis is congestion of the mucosal membranes caused by allergy or viral infection; resulting obstruction at the osteomeatal complex prevents clearance of bacteria. Not surprisingly, the bacteriology of acute maxillary sinusitis is similar to that of otitis media, with S. pneumoniae and/or Haemophilus influenzae being isolated in the great majority of cases. The majority of patients with pneumococcal pneumonia do not have detectable bacteremia, and it is very uncommon for the laboratory to isolate pneumococci from sputum of a patient who does not have a clear clinical picture of pneumonia or acute purulent tracheobronchitis. Empyema, the most common complication of pneumococcal pneumonia in the preantibiotic era, occurred in about 5% of cases and remains the most common today, with an incidence of approximately 2%. S. pneumoniae, despite its somewhat limited array of tissue-damaging enzymes and toxins, remains a prominent cause of infection with a surprisingly broad array of manifestations.