Invasion

Question 1

Which lytic substance does Clostridium use?

Answer 1

•collagenase
•breaks down collagen that forms connective tissue

Question 2

Which lytic substance does staphylococcus use?

Answer 2

•fibrinolysin (staphylokinase)
•digests fibrin clots that form a mesh cover over platelet plugs at wound sites

Question 3

Which lytic substance does Streptococcus use?

Answer 3

•hyaluronidase
•depolymerises hyaluronic acid- interstitial cement of connective tissue

Question 4

Clostridium, Staphylococcus and Streptococcus all use which lytic substance?

Answer 4

•DNase
•destroys DNA, lowers viscosity of exudates/pus which enhances bacterial motility

Question 5

How can intracellular pathogens survive the phagolysosome of phagocytes?

Answer 5

a) they live in the phagolysosome and are resistant to killing

b) they live in the phagosome and prevent phagosome-lysosome fusion

c) they escape the phagosome into cytoplasm

Question 6

How do bacteria invade non-phagocytic cells?

Answer 6

•attach to host surface (via adhesins)
•cause changes in cytoskeleton
•actin rearrangements
•pseudopod formation
•enter via invasins

Question 7

Explain the zipper mechanism of invasion of non-phagocytic cells

Answer 7

•invasins bind to host receptors
•actin polymerisation is triggered
•bacteria are surrounded by pseudopodia and engulfed into phagosome

Question 8

Explain the trigger mechanism of invasion into non-phagocytic cells

Answer 8

•bacteria inject host via T3SS
•activate changes to actin cytoskeleton, causing ruffles
•membrane ruffling leads to uptake of bacteria by host

Question 9

Name 2 bacteria which use the zipper mechanism

Answer 9

•Listeria
•Yersinia

Question 10

Name 2 bacteria which use the trigger mechanism

Answer 10

•Shigella
•Salmonella