Med Micro 11 - Listeria

Question 1

What do we mean by virulence is multifactorial?

Answer 1

More than one virulence factor

Question 2

What do we mean by virulence is multidimensional?

Answer 2

Gene regulation

Question 3

How is the “virulence process” represented in this diagram??

Answer 3

it is multifactorial and multidimensional! Which is which? Multidimensional means they are turned on and off at different times

Question 4

L. monocytogenes characteristics

Answer 4

Gram + rod; opportunistic intracellular pathogen

Question 5

Listeriosis

Answer 5

Infection from raw contaminated food; Clinical features range from mild influenza-like symptoms to meningitis and/or meningoencephalitis accompanied by septicemia. Infection of fetus is common

Question 6

Why is Listeria called a public health problem?

Answer 6

Because we can’t eradicate it

Question 7

What is another example of a public health problem?

Answer 7

Antibiotic resistance. Cannot win (yet)

Question 8

Why is Listeria so hard to eradicate?

Answer 8

It has such a large reservoir - animals and animal products (esp cows and dairy).

Question 9

What type of transmission is Listeria?

Answer 9

It is carried in food, so vehicle! (not zoonotic)

Question 10

Natural habitats and incidence of disease

Answer 10

Listera is carried by 5-10% human population; true incidence is not know. Leading cause of death in food borne bacterial pathogens

Question 11

Who is most affected by listeria?

Answer 11

affects primarily pregnant women, fetus, newborns, and adults with weakened immune systems. This means we fight it with cell-mediated response

Question 12

Why is it important to know the symptoms of Listeriosis?

Answer 12

Need to be able to diagnose

Question 13

Pathogenesis

Answer 13

Normally, immune system contains the infection; adults with no history have T cells primed by listeria antigens; generate biofilm, esp in response to bile at 37C; able to cross the intestinal barrier, the blood-brain barrier, and the placental barrier

Question 14

Growth at low temperature

Answer 14

You can achieve full growth at 4C! Problem even with refrigerated food.

Question 15

Describe the quorum sensing system in Listeria

Answer 15

AgrD-dependent quorum sensing affects biofilm formation, invasion, virulence and global gene expression profiles in Listeria monocytogenes. Autoinducer polypeptide binds to surface protein. - picture

Question 16

What regulates expression of the biofilm phenotype in Listeria?

Answer 16

Quorum sensing!!

Question 17

Listeria virulence factors

Answer 17

normally motile, but flagella are not produced at 37C (still required for biofilm formation in vitro). associated with the ability of the bacteria to move themselves into, within and between host cells (b/c they are intracellular pathogens)

Question 18

Listeria adherence and invasion

Answer 18

require internalin; induced by clathrin mediated endocytosis involving InlA which is only expressed at 37C (stimulates its own uptake); InlA and InlB required for crossing placenta

Question 19

Invasion and Escape

Answer 19

Once inside phagocytic cell - listeriolysin O (LLO) like hemolysin, degrade phagosome as pH decreases; ActA- Promotes the polymerization of actin, a component of the host cell cytoskeleton, on the bacterial surface - works like rocket; expression is regulated! Something about Macrophage or parenchymal cell

Question 20

How does it cross barriers?

Answer 20

Able to bind and be taken up by many cell types.

Question 21

How does Listeria infect new cells?

Answer 21

“Bounce” out in small bit of membrane, get phagocytosed, then break out into new cell. Can spread while avoiding Ab response

Question 22

How does Listeria cause septicemia if it is not generally exposed during transmission b/w cells?

Answer 22

The sheer number of pathogens is huge; and the large amount of nutrients.

Question 23

Main virulence factors

Answer 23

INLA and B: uptake; LLO: escape from endosome; ActA - polar manner - stimulates actin polymerization

Question 24

Life cycle review. Consider the relevant virulence factors in each stage (mutlifactorial or -dimensional)

Answer 24

Bind: InlA and B; Endocytosis; Lysis; Actin polymerization; Cell to cell spread. All regulated.

Question 25

Treatment of Listeria

Answer 25

If early, antibiotic treatment can prevent serious disease; Early diagnosis is unusual, since the first signs of a case or an outbreak are reports of stillbirth or serious infections

Question 26

Prevention of Listeria

Answer 26

Recalled processed foods known to be the source of Listeria that may still be in the market place, restaurant or home. Remember it grows at low temperature!

Question 27

Describe the different way in which Listeria subverts eukaryotic systems

Answer 27

4 ways! Getting endocytosed, escaping endosome, actin propulsion, taken up inside a piece of membrane

Question 28

Describe the immune response generated to a Listeria infection focusing on each sep in the process. In addition, describe the immune response generated i a latex bead coasted with InlA were injected under the skin

Answer 28

the bead will get taken up. whats the main difference? it wont be recognized by Ab response since it cannot esapce

Question 29

How does it cross placenta and blood-brain barrier?

Answer 29

Same way it crosses the intestine, Internalin-E-cadherin interaction

Question 30

How does it get to the blood brain barrier?

Answer 30

Listeria infects macrophages and uses them as a vector.

Question 31

For those with fully functional immune systems, Listeria is not a major issue. Why might this be the case?

Answer 31

Innate immunity: TLRs bind extracellular, NODs bind intracellular, macrophages ingest, antimicrobials are produced, and adaptive immunity is triggered. Adaptive: cells degrade some intracellular proteins, show on MHCI. Tc cells most involved in clearing infection.

Question 32

If your goal was to generate a most excellent vaccine for Listeria, how would you go about doing this?

Answer 32

Beautiful question! Live attenuated (mutate it so it can’t revert - but can’t use for old). Infect via normal route, so you get appropriate immune response

Question 33

For a listeria vaccine. What virulence factor would you discuss? Which would be the best?

Answer 33

Attenuated: INLA and B: no good, only part of response; LLO: no good, just killed; ActA: good - infects, reproduces, but cannot spread. Other options: Viroid - invade and deliver; Recombinant - produces MHCI and II, good.