Host-bacteria interactions Flashcards
What are virulence factors
Molecules that allow bacteria to adhere, invade, evade host defense, cause tissue damage, replicate or persist in the host
What is a virulence gene
Gene encoding a virulence factor
Describe the steps in the bacterial infection process
Adhesion
Invasion intra/extra cellular survival
Subversion of host defense
Replication
What do bacteria adhere to
cells
secretory products
Structural components
other bacteria
What structures cause adhesion of bacteria
- Fimbrae/ pili
- Adhesive macromolecules
- Capsules
- Flagellum
- Proteinaecious fibrils
How does adhesion effect bacteria
- express more proteins that allow survival in the host
- inhibition/ stimulation of growth
- induction of more adhesive structures
- synthesis and secretion of proteins required for invasion/ host submission
How does adhesion effect host cells
- altered morphology
- induction of fluid loss
- induction of cytokine release
- up-regulation of inter cellular adhesion molecules
apoptosis
What strategies are used by bacteria to survive host defense
- resistance to host defence
- Active subversion of host defence (killing of phagocytic cells and changing host cell)
Describe how bacteria resist host defence
- complement resistance
- avoiding phagocytosis
- Protection against recognition by antibodies
How do bacteria undermine host defense mechanisms
- Produce toxins
- produce superantigens
- bacterial effector proteins injected into host cells
What are superantigens?
Bacteria overly stimulate antigen presenting cells and T-cells causing excessive and uncoordinated release of pro-inflammatory cytokines causing toxic shock syndrome
How do bacteria get into cells
- Phagocytic cells - actively take up bacteria. Bacteria survive by either modifying vesicle trafficking or escaping the phagosome.
- Forced phagocytosis
How do bacteria move in the cytoplasm of host cells
Exploit the host cell cytoskeleton for intracellular movement
How do bacteria move between cells without being noticed by the host defense system
- Actin tails- can propel them for one cell straight into another
- During cell division- from mother to off-spring
Where do bacteria get nutrients in cytosolic bacteria
- Direct use of host cellular glucose
- promote host autophagy= degradation of complex host macromolecules to release amino acids
