Bacterial Intracellular Pathogens Flashcards
What is intracellular survival?
An organism being able to live within a host cell sometimes by modifying host mechanisms
Define facultative intracellular pathogen
A pathogen that could live inside a host cell but doesn’t need to in order to survive
Define obligate intracellular pathogen
A pathogen that needs to live inside a host cell to survive
Mechanisms of intracellular survial
- Avoid uptake if they can’t survive in the cell
- Taken up by phagocytosis but able to still survive in a vacuole
- Taken up by phagocytosis but can escape the vacuole and survive in cytoplasm
Host bactericidal mechanisms
- Acidification
- ROS
- RNI
- Antimicrobial peptides
- Enzymes
- Competitors
Host defense evasion mechanisms
.
Bactericidal resistance mechanisms
- Detoxification of killing agents: can convert reactive intermediates into less toxic substances
- Prevent access to killing agents: physical characteristics, thick cell wall, outer membranes gram neg
- Prevent iNOS activity: arginase secretion and repress iNOS expression to limit RNI production
Survives in phagosome, modify and resist defenses
Salmonella
Escapes from phagosome, kills macrophages and invades cells
Shigella
Salmonella virulence: Put in order
- Uptake by macrophages, spread
- If released from macrophage induce epithelial uptake at basolateral side (re-enter)
- Translocation
- Uptake into epithelial cells
- Induce apoptosis in macrophages, IL-1B and inflammation
1) Uptake into epithelial cells
2) Translocation
3) Uptake by macrophages, spread
4) Induce apoptosis in macrophages, IL-1B and inflammation
5) If released from macrophage induce epithelial uptake at basolateral side (re-enter)
What is a SCC
Salmonella containing compartment
What is a SCV
Salmonella containing vesicle
Salmonella evasion of macrophages (5)
- Arginase II: breaks down arginine to limit RNI production
- Stops fusion with lysosome: no enzyme activity
- Induces pyroptosis to escape
- Induces autophagy
- T3SS
