Which of the following bacteria is classically encapsulated and associated with asplenia risk?

• A. Streptococcus pneumoniae
• B. Escherichia coli
• C. Staphylococcus aureus
• D. Pseudomonas aeruginosa

Answer: (A)

Asplenia increases risk for infections with encapsulated bacteria because the spleen is essential for producing antibodies that opsonize polysaccharide capsules and promote their clearance from the bloodstream. Streptococcus pneumoniae is the classic encapsulated organism linked to this risk; its polysaccharide capsule shields it from phagocytosis, and without splenic function the body struggles to opsonize and eliminate it, leading to severe sepsis, pneumonia, or meningitis in asplenic individuals. The other bacteria listed can cause serious infections, but they are not the classic encapsulated pathogens specifically associated with asplenia-related risk.