Bacterial Pathogenesis

Question 1

What is a component or trait of a pathogen that allows it to cause disease in a susceptible host?

Answer 1

virulence factor

Question 2

What is the first Koch postulate?

Answer 2

The organism must be found in all cases of disease but generally not in healthy animals

Question 3

What is the limitation of the first Koch postulate?

Answer 3

sometimes the organism is long gone by the time disease symptoms appear

Question 4

What is the second Koch postulate?

Answer 4

The organism must be isolated from diseased animals and grown in pure culture

Question 5

What is the limitation of the second Koch postulate?

Answer 5

many organisms are not cultivatable

Question 6

What is the third Koch postulate?

Answer 6

The disease must be reproduced when the isolated organism is inoculated into susceptible animals

Question 7

What is the limitation of the third Koch postulate?

Answer 7

the disease may be specific to humans and it is not always ethical to test on humans

Question 8

What is the fourth Koch postulate?

Answer 8

The organism must be isolated in pure culture from the experimentally infected animal

Question 9

What is the limitation of the fourth Koch postulate?

Answer 9

many organisms are not cultivatable

Question 10

True or False? Pathogenecity is thought to be acquired in quantum leaps rather than through gradual evolution.

Answer 10

True

Question 11

What are Falkow’s postulates?

Answer 11

1. The gene(s) encoding the phenotype should be associated w/ pathogenic strains
2. Inactivation of the gene(s) results in a reduction in virulence
3. Restoration of the gene(s) into the avirulent mutant reestablishes virulence

Question 12

What is associated with Gram negative bacteria cell wall?

Answer 12

LPS (endotoxin)

Question 13

True or False? Most exotoxins are proteins?

Answer 13

True

Question 14

What is composed of Lipid A + Core polysaccharide + O antigen

Answer 14

Endotoxin

Question 15

What carries the endotoxin activity?

Answer 15

Lipid A

Question 16

What is the antigenic portion of LPS?

Answer 16

O side chain (O antigen)

Question 17

What is associated with overwhelming infection resulting in vascular system failure with sequestration of very large volumes of blood in capillaries and veins?

Answer 17

Septic Shock

Question 18

What can cause septic shock?

Answer 18

LPS

Question 19

What is it called when endotoxin in the blood?

Answer 19

endotoxemia

Question 20

Describe the roles of A and B in A-B dimeric exotoxin

Answer 20

B is associated with absorption to cell surface and transfer of A across membrane (B-binding, A-active)

Question 21

What are 6 examples of antiphagocytic substances?

Answer 21

capsule
K antigen
M protein/fimbriae
protein A
slime layer
O antigen

Question 22

What are the two major mechanisms by which pathogen escape phagocytosis?

Answer 22

antigen mimicry

antigenic variation

Question 23

When the pathogen is naturally coated with antigens closely related to host constituents or borrows host constituents to coat itself it is called?

Answer 23

antigen mimicry

Question 24

When the pathogen changes its antigenic coat periodically to evade immune response, it is called?

Answer 24

antigenic variation