Listeria

Question 1

What are the 3 pathogenic species of listeria?

Answer 1

Monocytogenes
Ivanovii
Seeligeri

Question 2

What are the 2 serotypes of monoctyogenes?

Answer 2

1/2a and 4b

Question 3

What is the method for sub-typing monocytogenes?

Answer 3

Whole genome sequencing

Question 4

Characteristics of monocytogenes

Answer 4

Gram +
Non-spore forming
Motile
Grows at low water activity (>0.9)
Wide range of pH (4.6-9.2)
Optimal growth at 37C and significant growth at 0C (psychotropic)

Question 5

Symptoms of listeria

Answer 5

Mild symptoms
If systemic can cause bacteraemia and meningitis

Question 6

How does listeria cause infection?

Answer 6

Infects GI tract and crosses intestinal mucosa through villi or junctions between goblet and epithelial cells

Question 7

How does listeria cause its uptake by the host?

Answer 7

Encodes surface proteins

Question 8

What is another method for listeria infection?

Answer 8

Zipper mechanisms causing uptake

Question 9

How does listeria enter the vacuole?

Answer 9

Internalins bind to receptor molecules on host cell, causes rearrangement in cell membrane and cytoskeleton causing listeria inside vacuole

Question 10

How can listeria effect organs and tissues?

Answer 10

Can be disseminated through the liver or spleen

Question 11

How can listeria cause neonatal infection?

Answer 11

When it crosses the placenta

Question 12

How does listeria move around the body?

Answer 12

Intracellular pathogens produce enzymes that allow escape from the vacuole. Also produce protein that uses host cell actin to move around the cell and onto the next. Ends up in a vacuole and repeats process

Question 13

How can listeria be cleared?

Answer 13

Cell-mediated immunity

Question 14

Where can listeria be found in the environment?

Answer 14

Soils (plant decay)
Animal guts (faeces and milk)
Factories (packaging, walls)

Question 15

Acceptable limit of listeria in 25g of ready to eat foods

Answer 15

<100cfu/g