8 - Listeria monocytogenes

Question 1

Typical Listeriosis outbreak:

Answer 1

hot dogs (make sure you cook your hot dogs)

Question 2

What are the 2 species of Listeria that are pathogenic:

Answer 2

• Listeria monocytogenes (humans)

- Listeria Ivanovii (cows)

Question 3

Characteristics of Lm:

Answer 3

• gram +
• psychrotrophic
• facultative anaerobe
• nonsporulating
• motile small rods

Question 4

it displays motility via its:

Answer 4

flagella

Question 5

Motility is temperature dependent; it is motile between _________

Answer 5

20-30C

Question 6

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

Answer 6

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

Question 7

Which lineages are responsible for most infections?

Answer 7

Lineage 1 and Lineage 2

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

Question 8

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

Answer 8

the nervous system and the placenta

Question 9

Listeria is a young/old pathogen?

Answer 9

young

Question 10

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

Answer 10

T

Question 11

Lm is an almost ubiquitous environmental ________________

Answer 11

saprophyte

Question 12

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

Answer 12

T

Question 13

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

Answer 13

refrigerator

Question 14

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

Answer 14

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

Question 15

Is Listeria sensitive to pasteurization temperatures?

Answer 15

Yes

Question 16

When Listeria is inside a _______ it can survive pasteurization

Answer 16

white blood cell

Question 17

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

Answer 17

because it has the ability to form biofilms

Question 18

What happens to Listeria when you lower the temperature ?

Answer 18

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

Question 19

Explain why raw milk cheeses are a source of Lm?

Answer 19

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

Question 20

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

Answer 20

F

Question 21

Contamination of animal muscle can happen ________ or ________ slaughter

Answer 21

during or after

Question 22

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

Answer 22

These meats are heated and then cooled in brine

Question 23

Listeria infection is ___________ but mortality is ___________

Answer 23

uncommon

high

Question 24

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

Answer 24

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

Question 25

What is the infection process / route followed by Listeria

Answer 25

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

Question 26

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

Answer 26

Kupffer

Question 27

The lymph and blood can also carry Lm to the ________________

Answer 27

blood-brain barrier

Question 28

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

Answer 28

intracellular

Question 29

How does Lm infect epithelial cells?

Answer 29

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

Question 30

What are goblet cells?

Answer 30

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

Question 31

How does Lm infect goblet cells?

Answer 31

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

Question 32

How does Lm infect macrophages?

Answer 32

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

Question 33

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

Answer 33

placenta

Question 34

How does Lm infect trophoblasts ?

Answer 34

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

Question 35

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

Answer 35

T

Question 36

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

Answer 36

bacteriocin

Question 37

The core Lm virulon is regulated by the _____ promoter

Answer 37

PrfA

Question 38

If the loop is present, prfA will be _________

Answer 38

weakly active

Question 39

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

Answer 39

T

Question 40

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

Answer 40

- the intestinal barrier - the blood brain barrier - the placental barrier

Question 41

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

Answer 41

well conserved