Bacterial Pathogenesis: 11.7.2022. and 11.9.2022. Study Questions

Question 1

What is the function of a siderophore?

Answer 1

iron-binding substance produced by bacteria to scavenge iron

Question 2

describe the mechanisms bacteria use to avoid IgA

Answer 2

• IgA proteases: enzymes that degrade IgA

Question 3

describe the function of type III secretion systems

Answer 3

allow bacteria to transfer gene products directly into host cells

Question 4

describe two outcomes of effector proteins that promote actin polymerization

Answer 4

• ruffling of the cell surface
• actin tails

Question 5

what are the two mechanisms by which bacteria can breach mucous membranes

Answer 5

• directed uptake by cells
• exploiting antigen-sampling processes

Question 6

what advantages does an intracellular bacterium have?

Answer 6

protected by two host cells that fused, avoiding antibodies

Question 7

describe three mechanisms of avoiding phagocytosis

Answer 7

• capsules
• M protein
• Fc receptors

Question 8

how are endotoxins different from exotoxins?

Answer 8

USE CHART

Question 9

what is a medically relevant application of discovering that a toxin is an AB toxin?

Answer 9

A: active
B: binding

inhibit/mutate A subunit? toxin cannot cause damage
inhibit/mutate B subunit? toxin cannot enter cell

Question 10

describe the most relevant features of tetanus. for instance:
air needs?
G+ or G-?
where is it found?
spore-forming?

Answer 10

obligate anaerobe, Gram-positive, terminal spore-former, found in soil

Question 11

what is the primary mechanism of pathogenesis for tetanus?

Answer 11

invasion of tissue followed by toxin production.

puncture wound –> spores in tissue –> germinate if anaerobic –> vegetative cells multiply, produce toxin

Question 12

describe the most relevant features of diphtheria. for instance:
G+ or G-?
shape?
spore-forming?
air needs?

Answer 12

Gram-positive rod, non-spore-forming, facultative

Question 13

what is the primary mechanism of pathogenesis for diphtheria?

Answer 13

spread through the air from infected people. colonizes throat (mucous membrane), produces toxin.

Question 14

what would be the effect of removing endotoxin from a bacterium? (3)

Answer 14

• endotoxin contains LPS. removing endotoxin removes LPS, which contains lipid A. Lipid A is used to help clear an infection
• LPS triggers innate immunity, so if it was removed, our body would have a more difficult time detecting the pathogen
• LPS can be dangerous, as systemic response can cause septic shock, so its removal could also be beneficial to humans

Question 15

do people who acquire botulism have to have bacteria in their body to get the disease?

Answer 15

nope! the bacterial cells produce a toxin which people consume, causing symptoms to arise

Question 16

how can the immune response cause damage?

Answer 16

strong and widespread immune response can cause damage. for instance, if the immune response responds to a systemic problem rather than a local problem, it can lead to sepsis, a dramatic drop in blood pressure, septic shock, widespread blood clotting, and disseminated intravascular coagulation.

Question 17

name the most relevant features of gonorrhea that make it a highly successful pathogen (6)

Answer 17

omp-pi-lo-pro give few compliments.

1. OMP
2. Pilus
3. LOS
4. Release IgA proteases
5. Prevents phagolysosome fusion
6. Binds complement regulator

Question 18

why are so many people with gonorrhea asymptomatic?

Question 19

describe the pathogenesis of Neisseria gonorrhoeae.

Answer 19

• GC uses its pili to attach to receptors on non-ciliated columnar mucosal cells. can’t adjust to squamous epithelium.
• once they attach, some bacterial cells grow on the surface, but others direct the host cells to engulf them
• there, they can multiply within the protected environment of the epithelial cell or are released to the other side of the mucosal barrier

Question 20

what gives rise to symptoms of the disease caused by Neisseria gonorrhoeae?

Answer 20

the intense inflammatory response that results from infection

Question 21

describe “directed uptake by cells” as a mechanism of penetrating the mucous membrane and give example of a pathogen that does this.

Answer 21

• attaching to a cell and to induce endocytosis
• use a type III secretion system to deliver proteins to cells
• engulfment of bacteria/rearranging a cell’s actin results in membrane ruffling
• ex. Salmonella species

Question 22

describe “exploiting antigen-sampling processes” as a mechanism of penetrating the mucous membrane, and give an example of a pathogen that does this.

Answer 22

• using the MALT process to cross the membranes
• passing through an M cell and being taken up by macrophages, then attaching to epithelial cells and using host actin to polymerize, which propels them to the next cell over
• ex. Shigella species

Question 23

what is membrane ruffling?

Answer 23

mechanism of engulfment that some bacteria induce by triggering rearrangements of a cell’s actin

Question 24

what is MALT? what does it stand for?

Answer 24

mucosa-associated lymphoid tissue

lymphoid tissue present in the mucosa of the respiratory, GI, and gnitourinary tracts

Question 25

how do capsules help cells avoid phagocytosis

Answer 25

distinct, thick gelatinous material that surrounds some microorganisms

Question 26

how do M proteins help cells avoid being recognized by pathogens

Answer 26

component of Strep cell wall that binds a complement regulatory protein that inactivates C3b, preventing C3b from being an effective opsonin and activating the complement system

Question 27

how do Fc receptors help cells avoid being recognized by pathogens

Answer 27

Fc attaches, Fab sticks out, not recognized by phagocytes

Question 28

how does OMP help gonorrhoeae avoid the immune system?

Answer 28

binds TCR and prevents activation, inhibits adaptive immunity

Question 29

how does LOS help gonorrhoeae avoid the immune system?

Answer 29

Invisibility cloak

Question 30

how do pili help gonorrhoeae avoid the immune system?

Answer 30

antigenic variation, phase variation