A

The spleen is critical for opsonizing and clearing polysaccharide-encapsulated organisms; after splenectomy the risk of overwhelming sepsis from Streptococcus pneumoniae, Haemophilus influenzae type b, and Neisseria meningitidis rises sharply, making encapsulated bacteria the key threat [Polák 2012, PMID 23094812; Castagnola 2003, PMID 14667194; Chong 2017, PMID 27776576].