Bacterial Pathogenesis

Question 1

State Koch’s postulates

Answer 1

Organism found in all patients with the disease

Distribution relates to lesions

Cultivate outside host for several generation

Reproduce in other species

Demonstrate immune response

Question 2

Bacterial adherence example

Answer 2

Fimbriae to Oligosaccharide

ETEC via CS3

Question 3

How does the pathogen enter host?

Answer 3

Pathogens can invade through cells or between cells. By adhering first then invading. This is done via pathogen mediated endocytosis being initiates by bacterial surface proteins. Eg Enteropathogenic Yersinia into M cells. Yersinia has outer membrane invasin which binds integrin on M cells.

Question 4

Overcoming Phagocytosis

Answer 4

Direct evasion of phagocytosis- leukocidins (kill phagocytes), anti-inflammatory toxins or encased in anti-phagocytic structures (capsules) via electrostatic repulsion resembling host components and masking underlying structures.

Question 5

How pathogens resist killing by phagocytes which use lysosomes, ROS and RNS

Answer 5

Inhibit respiratory burst (phagocytes producing reactive O2 and metabolise rapidly)

Prevent phagolysosome formation

Escape vacuole

Resist Bactericidal