CNS Infections- Listeriosis Flashcards
1
Q
Description of Listeriosis
A
- Gram positive, coccobacilli (rod), motile, coryneform species
- Not fastidious.
- Growth temperature range is broad (0→50C). -Isolated by cold enrichment
- Facultative intracellular pathogens
- 3 major serotypes
- pregnant women are at an increased risk
- summer seasonality
2
Q
Virulence factors
A
- Lipoteichoic acids: Immunomodulator as potent as & acts similar to endotoxin.
- Proteins: enzymes required for organism-directed phagocytosis and cell-to-cell spread.
3
Q
Transmission
A
- food born
- human-to-human (vertical, transplacentral in utero and during parturition but less common)
- animal to human
4
Q
Reservoirs
A
- ubiquitous
- soul, water, normal fecal flora, food
5
Q
Risk factors
A
Immunosuppression - T cell suppression
6
Q
Pathogenesis (4 steps)
A
- POE is GIT; Agent is phagocytized by GI cells (without damaging the integrity of the GI tract) and macrophages (agent survives in non-activated macrophages).
- Surface proteins induce nonprofessional phagocytic cells to phagocytize Listeria and mediate entry into epithelial cell.
- Enzymes (listeriolysin O) disrupt the phagosome membrane allowing Listeria cells to escape from the host vacuole and replicate in the host cell cytoplasm.
- A tail of polymerized actin filaments form at the ends of the Listeria cells (made by virulence factors, like ActA) and induce cell-to-cell infection
7
Q
Organism has a tropism for:
A
- CNS (meninges and brain, especially the brain-stem) and is capable of penetrating and infecting brain parenchyma (usually brain stem)
- Placenta
8
Q
Incubation period may be _________
A
long (about 30 days; range is 11→70 days)
9
Q
Immunity formed is
A
Primarily T cell-mediated immunity
control of infection requires activated macrophages, which can only kill stationary (latent) phase Listeria.
10
Q
Infections in pregnancy
A
- Illness usually occurs in the 3rd trimester, with the greatest decline in gravid female’s CMI.
- Gravid female manifests with acute, febrile illness - severe flu-like symptoms due to bacteremia.
- Mother rarely manifests with CNS infection
11
Q
Fetal (in utero) infection causes:
A
- early-onset sepsis syndrome,
- spontaneous abortion (from 5m gestation on),
- stillborn
- premature births.
Fetal mortality rate is high (15→50%)
12
Q
Early-onset sepsis syndrome:
A
- is associated with prematurity.
- Infection is likely acquired in utero via inhalation of infected amniotic fluid.
- Agent is found in neonate practically everywhere (in the: external ear, nose, throat, blood, CSF, high concentrations in gut and lungs
- Symptoms manifest in newborn (
13
Q
Granulomatosis infantisepticum is a rare condition involving in utero infection:
A
- Agent is found in disseminated abscess and/or granulomas in multiple internal organs, esp. liver & spleen.
- papules in throat, skin may also be present
- Neonate mortality rate is high (>50%)
14
Q
Late-onset meningoencephalitis:
A
- Infection occurs during or after birth
- Symptoms manifest in between 1-2 weeks postpartum
- Neonate mortality rate is moderate (10-20%)
- Mother is asymptomatic
15
Q
Listeria has tropism for _______
A
brain, esp. brain stem
