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Fpathogens > 8 - Listeria monocytogenes > Flashcards

8 - Listeria monocytogenes Flashcards

1
Q

Typical Listeriosis outbreak:

A

hot dogs (make sure you cook your hot dogs)

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2
Q

What are the 2 species of Listeria that are pathogenic:

A
  • Listeria monocytogenes (humans)

- Listeria Ivanovii (cows)

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3
Q

Characteristics of Lm:

A
  • gram +
  • psychrotrophic
  • facultative anaerobe
  • nonsporulating
  • motile small rods
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4
Q

it displays motility via its:

A

flagella

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5
Q

Motility is temperature dependent; it is motile between _________

A

20-30C

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6
Q

There are 13 serotypes of Lm though 95% of outbreaks are caused by:

A

1/2a, 1/2b, 4b

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7
Q

Which lineages are responsible for most infections?

A

Lineage 1 and Lineage 2

*Lineage 1 has affinity for the brain/placenta (serious / deadly)

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8
Q

Lineage 1 Lm appears to be more virulent, as these CCs appear to have trophism for :

A

the nervous system and the placenta

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9
Q

Listeria is a young/old pathogen?

A

young

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10
Q

T OR F: Lm may have emerged as a pathogen relatively recently potentially in association with the increased movement of humans, animals, and food

A

T

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11
Q

Lm is an almost ubiquitous environmental ________________

A

saprophyte

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12
Q

T OR F: Some humans carry Lm without symptoms (either in the intestine or gall bladder)

A

T

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13
Q

It can grow and divide from 4-45C, it grows in the _______________ and outcompetes other bacteria in this environment

A

refrigerator

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14
Q

It can grow in media as low as pH ___ and in salt contents as high as ____

A

4.4
10
*hurdle concept: heat resistance increases as salt content decreases

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15
Q

Is Listeria sensitive to pasteurization temperatures?

A

Yes

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16
Q

When Listeria is inside a _______ it can survive pasteurization

A

white blood cell

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17
Q

Why does Listeria persist for years once established in a food-processing plant?

A

because it has the ability to form biofilms

18
Q

What happens to Listeria when you lower the temperature ?

A

It doesn’t stop Lm growth but it does slow it

19
Q

Explain why raw milk cheeses are a source of Lm?

A

Raw milk cheeses are unpasteurized , Lm survives well during cheese manufacturing due to both the temperature (cold) as well as the salt content (high) - while many of its competitors die

20
Q

T OR F: it is recommended for pregnant women and those who are immuno-compromised to eat raw milk cheeses

A

F

21
Q

Contamination of animal muscle can happen ________ or ________ slaughter

A

during or after

22
Q

Explain why cold-meats / ready-to-eat meats are a good source of Lm:

A

These meats are heated and then cooled in brine

23
Q

Listeria infection is ___________ but mortality is ___________

A

uncommon

high

24
Q

What are the main symptoms associated with Listeria for healthy people vs immunocompromised people:

A
  • most individuals will experience mild gastroenteritis
  • immunocompromised/ pregnant women will experience sepsis, meningitis, infection of the fetus leading to abortion or other pregnancy complications
25
Q

What is the infection process / route followed by Listeria

A

1) you ingest Lm from contaminated food
2) you absorb it in your intestine
3) goes to the lymph node
4) goes to liver/spleen
5) goes to brain/placenta

26
Q

In the liver _____ cells phagocytose Lm cells and they succumb to necroptosis

A

Kupffer

27
Q

The lymph and blood can also carry Lm to the ________________

A

blood-brain barrier

28
Q

Lm is an ______________ bacterial pathogen and can be taken up by non-phagocytic cells, such as epithelial cells, or phagocytic cells

A

intracellular

29
Q

How does Lm infect epithelial cells?

A

1) Lm enters epithelial cells through receptor-mediated endocytosis
2) InlA and InlB bind to the cell receptors E-cadherin and Met
3) Once inside the host cell, Lm uses LLO and phospholipase A and B for vacuole rupture and escape
* Lm can also polymerize actin and use this to become motile to spread laterally from cell to cell

30
Q

What are goblet cells?

A

They are specialized epithelial cells that line mucosal surfaces and have a role in barrier maintenance through the secretion of mucus

31
Q

How does Lm infect goblet cells?

A

1) In goblet cells lnlA binds to E-cadherin which leads to receptor clustering, E-chaderin phosphorylation and ubiquitylation and subsequent bacterial up-take by the cell
2) In goblet cells, Lm remains internalizaed in the vacuole and rapidly transcytoses through the cell

32
Q

How does Lm infect macrophages?

A

1) Macrophages are phagocytic cells which actively phagocytize Lm cells
2) In macrophages, Lm can replicate in spacious listeria containing phagosome (SLAPs)
3) In SLAPs, Lm expresses intermediate levels of LLO which inteferes with the pH gradient that is required for acidification of the phagosome - but is not enough to promote phagosomal rupture

33
Q

Trophoblasts are cells that will form the ________, which are derived from the fetal tissue and form the external layer of the developing blastocyst in the context of pregnancy

A

placenta

34
Q

How does Lm infect trophoblasts ?

A

1) in trophoblasts InlB binds Met and induces phosphorylation and ubiquitylation and receptor-mediated endocytosis

35
Q

T OR F: In the intestinal lumen Lm encounters other bacteria that belong to the microbiome

A

T

36
Q

Lm produces a _____________ known as listeriolysin S (LLS) that restricts the growth of common commensals such as Allobaculum, Streptococcus, Alloprevotella

A

bacteriocin

37
Q

The core Lm virulon is regulated by the _____ promoter

A

PrfA

38
Q

If the loop is present, prfA will be _________

A

weakly active

39
Q

T OR F: Lm is a very serious food-borne infection which can result in systemic infection, meningitis or encephalitis and abortion in pregnant females

A

T

40
Q

Lm is an intracellular disease and can cross 3 important barriers:

A
  • the intestinal barrier
  • the blood brain barrier
  • the placental barrier
41
Q

Are the virulence factors of listeria well conserved or constently changing?

A

well conserved

Fpathogens (23 decks)

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