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mlsci 242 > LECTURE - Listeria > Flashcards

LECTURE - Listeria Flashcards

1
Q

Listeria monocytogenes is motile at these temperatures

A

20 degrees C by polar flagella

37 degrees C by causing actin polymerization within target cells

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2
Q

T or F. L. monocytogenes can form biofilms

A

T!

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3
Q

One of the few organisms that can cross the placenta

A

Listeria monocytogenes

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4
Q

This mediates L. monocytogenes attachment and internalization

A

Internalin A and Internalin B

  • InlA binds to mammalian receptor E-cadherin and is sufficient for invasion of cells in the intestines
  • it is also required along with InlB for invasion of the placenta (likely in brain microvessels as well to cause meningitis)
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5
Q

Inl B needs to bind to this receptor for hepatocyte growth factor (HGF) and is required for invasion of cells in placenta

A

Met

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6
Q

Listeriolysin O

A
  • b hemolysis on BAP
  • pore-forming toxin; to escape phagosome and grow in cytoplasm of infected cells
  • LLO mutants have LD50 that’s 10^5 higher than wild type; mutants can’t survive in macrophages
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7
Q

These are important in limiting spread of L. monocytogenes

A

CD8+ cytotoxic T lymphocytes and NK cells (intracellular organism); intracell growth of listeria outside an endosome or phagosome triggers this response

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8
Q

____ expression is important as it activates macrophages and this will kill Listeria

A

IFN-y

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9
Q

wide range of temperature growth for L. monocytogenes

A

4 to 40 degrees C

room temp to refrigerated temps (enhances infective dose)

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10
Q

why does L. monocytogenes growth look like an umbrella?

A

organisms swimming up looking for better O2 levels

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11
Q

Large number of ingested organisms of Listeria is required to cause disease in adults

A

10^9

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12
Q

incubation period of listeria

A

30 days on average

- if stomach pH is raised, infectious dose can be lowered

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13
Q

Why does pregnancy increase susceptibility to listeria infection?

A

likely due to a switch in Th2-response predominantly

- intracellular pathogen SHOULD elicit Th1 response

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13
Q

Why does pregnancy increase susceptibility to listeria infection?

A

likely due to a switch in Th2-response predominantly

- intracellular pathogen SHOULD elicit Th1 response

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14
Q

fatality rate of Listeriosis

A

20-30%

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15
Q

ActA

A
  • actin nucleator
  • on surface of listeria
  • focus for nucleation of actin filaments which propel bacteria through cytoplasm of host cell
  • has to be phosphorylated to be active; may be localized to one pole of the bacterial cell
16
Q

phosphoinositol-specific phospholipase C (plcA)

& phosphatidylcholine (non-specific) phospholipase C (plcB)

A
  • Listeria hemolysins (as is LLO)

- act synergistically; 500 fold reduction in virulence if both are missing

17
Q

PlcA

A

involved in the escape from primary phagocytic vacuole

18
Q

PlcB

A

involved in the escape from the double membrane vacuole

- requires cleavage by Mpl, a zinc-dependent protease, for activity in supernatants

19
Q

PlcA and PlcB

A

both can affect signal transduction in cells by releasing either diacylglycerol or ceramide from their target molecules, affecting Ca2+ release, and altering expression of the signal transduction molecules MAP-kinase and NF-kB

20
Q

T or F. Listeria invasion across placenta involves internalin B and leads to septicemia

A

T!

21
Q

This is probably not necessary for ingestion of bacteria by macrophage-like cells which are naturally phagocytic, but is essential for invasion of cells like enterocytes

A

InlA

22
Q

two-step invasion and intracellular spread of Listeria happens in these cells

A

macrophages, liver cells, endothelial cells, enterocytes

23
Q

this encodes for LLO

A

hly

24
Q

T or F. Listeria plaque formation does not require hemolysins

A

F! needs them; can restore plaque formation if add LLO back

25
Q

Best solution for listeriosis

A

prevention bc race against time (antibiotics useful only if disease is diagnosed in time)

  • wash raw veggies
  • avoid unpasteurized milk and soft cheeses
  • processed meats (e.g. hotdogs) should be thoroughly heated
26
Q

Erysipelothrix rhusiopathiae

A
  • gram pos rod
  • non-motile
  • asporogenous
  • facultative anaerobe
  • most common in swine
27
Q

occupational hazard associated with infected animals

A

E. rhusiopathiae

28
Q

three clinical categories for disease caused by E. rhusiopathiae

A
  • Erysipeloid: localized cutaneous form (most common); signs usually a throbbing itching pain and swelling of finger or part of hand
  • generalized cutaneous form
  • septicaemia (associated with endocarditis)
29
Q

diagnosis of E. rhusiopathiae

A

requires isolation of organism from wound (for confirmation)

30
Q

treatment of E. rhusiopathiae

A

penicillin or ampicillin

mlsci 242 (39 decks)

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