Bacterial Pathogenesis: 11.7.2022. and 11.9.2022. Study Questions Flashcards
What is the function of a siderophore?
iron-binding substance produced by bacteria to scavenge iron
describe the mechanisms bacteria use to avoid IgA
- IgA proteases: enzymes that degrade IgA
describe the function of type III secretion systems
allow bacteria to transfer gene products directly into host cells
describe two outcomes of effector proteins that promote actin polymerization
- ruffling of the cell surface
- actin tails
what are the two mechanisms by which bacteria can breach mucous membranes
- directed uptake by cells
- exploiting antigen-sampling processes
what advantages does an intracellular bacterium have?
protected by two host cells that fused, avoiding antibodies
describe three mechanisms of avoiding phagocytosis
- capsules
- M protein
- Fc receptors
how are endotoxins different from exotoxins?
USE CHART
what is a medically relevant application of discovering that a toxin is an AB toxin?
A: active
B: binding
inhibit/mutate A subunit? toxin cannot cause damage
inhibit/mutate B subunit? toxin cannot enter cell
describe the most relevant features of tetanus. for instance:
air needs?
G+ or G-?
where is it found?
spore-forming?
obligate anaerobe, Gram-positive, terminal spore-former, found in soil
what is the primary mechanism of pathogenesis for tetanus?
invasion of tissue followed by toxin production.
puncture wound –> spores in tissue –> germinate if anaerobic –> vegetative cells multiply, produce toxin
describe the most relevant features of diphtheria. for instance:
G+ or G-?
shape?
spore-forming?
air needs?
Gram-positive rod, non-spore-forming, facultative
what is the primary mechanism of pathogenesis for diphtheria?
spread through the air from infected people. colonizes throat (mucous membrane), produces toxin.
what would be the effect of removing endotoxin from a bacterium? (3)
- 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
do people who acquire botulism have to have bacteria in their body to get the disease?
nope! the bacterial cells produce a toxin which people consume, causing symptoms to arise
how can the immune response cause damage?
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.
name the most relevant features of gonorrhea that make it a highly successful pathogen (6)
omp-pi-lo-pro give few compliments.
- OMP
- Pilus
- LOS
- Release IgA proteases
- Prevents phagolysosome fusion
- Binds complement regulator
why are so many people with gonorrhea asymptomatic?
describe the pathogenesis of Neisseria gonorrhoeae.
- 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
what gives rise to symptoms of the disease caused by Neisseria gonorrhoeae?
the intense inflammatory response that results from infection
describe “directed uptake by cells” as a mechanism of penetrating the mucous membrane and give example of a pathogen that does this.
- 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
describe “exploiting antigen-sampling processes” as a mechanism of penetrating the mucous membrane, and give an example of a pathogen that does this.
- 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
what is membrane ruffling?
mechanism of engulfment that some bacteria induce by triggering rearrangements of a cell’s actin
what is MALT? what does it stand for?
mucosa-associated lymphoid tissue
lymphoid tissue present in the mucosa of the respiratory, GI, and gnitourinary tracts
how do capsules help cells avoid phagocytosis
distinct, thick gelatinous material that surrounds some microorganisms
how do M proteins help cells avoid being recognized by pathogens
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
how do Fc receptors help cells avoid being recognized by pathogens
Fc attaches, Fab sticks out, not recognized by phagocytes
how does OMP help gonorrhoeae avoid the immune system?
binds TCR and prevents activation, inhibits adaptive immunity
how does LOS help gonorrhoeae avoid the immune system?
Invisibility cloak
how do pili help gonorrhoeae avoid the immune system?
antigenic variation, phase variation
