Encapsulated organisms are particularly dangerous in asplenic individuals. Which organism is encapsulated and a common cause of pneumonia?

Encapsulated organisms are particularly dangerous in asplenic individuals. Which organism is encapsulated and a common cause of pneumonia?

• A. Listeria monocytogenes
• B. Pseudomonas aeruginosa
• C. Streptococcus pneumoniae
• D. Clostridium difficile

Answer: (C)

When the spleen is absent, clearing encapsulated bacteria becomes much harder. The capsule around many bacteria is a major defense against phagocytosis, so our splenic immune system relies on antibodies against those capsules (especially IgM) and on splenic macrophages to opsonize and remove these organisms. Without the spleen, encapsulated bacteria can spread more easily and cause severe infections. Streptococcus pneumoniae is a classic encapsulated organism and a leading cause of community-acquired pneumonia. Its polysaccharide capsule is the key virulence factor that helps it resist phagocytosis; in individuals without a spleen, the inability to efficiently opsonize and clear this capsule-containing bacterium makes pneumococcal pneumonia particularly dangerous. The other organisms listed are not the typical encapsulated organisms most associated with splenic defense in the context of pneumonia, or they are not primarily linked to this specific scenario.

When the spleen is absent, clearing encapsulated bacteria becomes much harder. The capsule around many bacteria is a major defense against phagocytosis, so our splenic immune system relies on antibodies against those capsules (especially IgM) and on splenic macrophages to opsonize and remove these organisms. Without the spleen, encapsulated bacteria can spread more easily and cause severe infections.

Streptococcus pneumoniae is a classic encapsulated organism and a leading cause of community-acquired pneumonia. Its polysaccharide capsule is the key virulence factor that helps it resist phagocytosis; in individuals without a spleen, the inability to efficiently opsonize and clear this capsule-containing bacterium makes pneumococcal pneumonia particularly dangerous. The other organisms listed are not the typical encapsulated organisms most associated with splenic defense in the context of pneumonia, or they are not primarily linked to this specific scenario.