lecture 7

Question 1

example of viruses

Answer 1

H1N1 Influenza virus

single stranded RNA, eveloped

Question 2

example of bacteria

Answer 2

Bacillus anthracis
Gram positive endospore-forming, rod-shaped bacterium
plasmids produce toxin, capsule

Question 3

Gram positive bacteria

Answer 3

retain crystal violet

have thick cell walls peptidoglycan

Question 4

Gram negative bacteria

Answer 4

do not retain crystal violet
have cell walls with 2 layers; a thin peptidoglycan layer and a thick outer membrane that contains polysaccharides bonded to lipids

Question 5

why is gram positive/negative identification important

Answer 5

to design drugs which target bacteria

Question 6

koch’s postulates

Answer 6

1. The pathogen must be present in every individual with the disease
2. A sample of the microorganism taken from the diseased host can be grown in put culture
3. A sample of the pure culture causes the same disease when injected into a health host
4. The microorganism can be recovered from the experimentally infected host

Question 7

exceptions to koch’s postulates

Answer 7

Treponema pallidum microbe cannot be cultured

Vibrio cholera pathogen can be found in healthy hosts

Question 8

Key stages of microbial pathogenesis

Answer 8

1. Adherance to host cells-
   - adhesins bind to host cells-
2. Invasion of host tissue
   - motility flagellae (through mucus)
   - internalin-related proteins (lnlB)
3. Replication within host tissues
   - siderophores (bind iron)
   - capsules (resist phagocytosis)
4. Disease causing damage to host tissues (pathology)
   - Toxic virulence factors-
   endotoxins: cause inflammation
   exotoxins: can be fatal

Question 9

3 types of exotoxin

Answer 9

1. Cytotoxin: lysis of RBCs (Staphylococcus pyrogenes)
2. Neurotoxin: causes paralysis (Clostridium botulinum)
3. Enterotoxin: causes severe dysentery (Shiga toxin)

Question 10

Endotoxins

Answer 10

Lipopolysaccharides LPS are found in outer mebrane of gram negative bacteria elicit strong immune responses