Host immune defects predisposing to meningitis

Host problem	Organism favored	Frequency of defect actually leading to infection
Absence of opsonizing antibody	Streptococcus pneumoniae	Common in all age groups
Absence of opsonizing antibody	Haemophilus influenzae	Common in very young children
Asplenia: surgical or functional	S. pneumoniae	Rare
Asplenia: surgical or functional	Neisseria meningitidis	Very rare
Complement deficiency	N. meningitidis	Very rare
Glucocorticoid excess	Listeria monocytogenes	Rare
Glucocorticoid excess	Cryptococcus neoformans	Rare
HIV infection	C. neoformans	About 5 percent eventually get cryptococcal meningitis
	S. pneumoniae	Common presenting illness
	L. monocytogenes	Rare
Bacteremia/endocarditis	Staphylococcus aureus; various gram-negative rods	Rare
Basilar skull fracture	S. pneumoniae; other upper respiratory tract flora	Very rare

HIV: human immunodeficiency virus.

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