Listeria monocytogenes spread - Answer-Invade non-phagocytes (InIA - E Cadherin)
-Lyse the phagosome (Listeriolysin O [LLO])
-LLO toxin enters the cytoplasm
-Utilize host actin to spread from cell-to-cell
Invade through the mucosal surface into the bloodstream (septicemia)
Cross the BBB (inflammation causes BBB permeability)
How does Listeria monocytogenes escape host defenses? - Answer--Intracellular
-Infects macrophages (escapes vacuole)
-Peptidoglycan deacetylation (TLR-2)
How does Listeria monocytogenes cause damage in bacterial meningitis? - Answer--
Inflammation (triggered by peptidoglycan)
-Fluid accumulation
-Increased intracranial pressure
-Hydrocephalus and brain damage (permanent)
OUTCOMES
HIGHLY LETHAL IF NOT TREATED
, NON-COMMUNICABLE EXCEPT FOR MOTHER TO BABY
Haemophilus influenzae Type B - Answer--Gm(-) rod
-Encapsulated (Type B antigen)
-All other types are less likely to causes disease
-Primary cause of bacterial meningitis in children 6 months to 2 years
-Vaccine available (almost eliminated it)
-
HiB encounter - Answer--Humans only
-Respiratory droplet or saliva
-Can be endogenous (sets up shop slowly)
HiB spread - Answer-Invade from URT into blood, then cross the blood-brain barrier to
CNS
HiB growth requirements - Answer-Fastidious, requires chocolate agar
How does HiB evade host defenses? - Answer--Extracellular
-Capsule
-Phosphorylcholine decoration of LOS (tricks anti-LOS IgG)
-Sialylation of LOS
-Binds complement factor H
-IgA protease
How does HiB cause damage to host? - Answer--Inflammation
-LPS
-Protein D - ciliated epithelium (glycerophosphodiesterase)
HiB infection outcomes - Answer--Death
-Neurological sequellae
-Transmission to new host (droplet/saliva)
HiB vaccine - Answer--Humoral IgG against capsule prevents systemic infection by
opsonization
-Composed of type B carbohydrate coupled to protein
-Drastically reduced meningitis by HiB
-Single serological type of capsule makes vaccination easier and more effective
-Part of the standard infant/childhood regimen
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