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How do we encounter Listeria monocytogenes?
Mainly on environment-soil or foods contaminated with it.
Through the genital tract of the mother in neonatal meningitis.
How does Listeria monocytogenes enter?
oral or transplacental
How does Listeria monocytogenes spread?
- It can invade non-phagocytes (InIa binds to E Caherin)
- It lyses the phagosome (Listeriolysin O LLO), escapes into the
cytoplasm, and uses host actin to spread cell to cell (ActA). - It can
invade through the mucosal surface into the bloodstream and cross the
blood/brain barrier.
,How does Listeria monocytogenes evade defenses?
- It is intracellular
- infects macrophages, escapes their vacuole and lives in cytoplasm.
- by deacetylation of peptidoglycan, so it does not get recognized by
TLR2.
What is the damage and outcome of Listeria monocytogenes?
Damage: inflammation (triggered by peptidoglycan) and fluid acumulation
whichi increases intracranial pressure, hydrocephalus and brain damage.
Outcome: lethal if untreated, not transmited between humans besides
transplacentaly from mom to baby.
,Haemophilis influenzae B (HiB) is a Gram ____ rod that is ___ _.
negative, encapsulated (type B antigen).
HiB is the primary cause of meningitis in ?
Children 6 month old to 2 years old.
What is the encaunter in HiB?
Human only, spread by droplets or saliva, can be endogenous or
exogenous.
, What is the entry mechanism of HiB?
URT (nasopharynx) adheres via fimbriae.
it has a protein Hap (Haemophilus adhesion and penetration), an
autotransporter protein (mediates its transport from periplasm through
the membrane to out of the cell).
Does HiB spread ?
Yes, all meningitis-causing organisms have to.
URT -> blood -> BBB -> CNS
HiB multiplication
- Chocolate agar, fastidious
How does HiB evade defenses ?
Extracellular, has a capsule (antiphagocytic)
- (sialation of LOS) antigenic mimicry
- binds complement factor H
- IgA protease