Lecture 27 - Host/Pathogen Interactions

Question 1

What is balanced pathogenicity? How does it shape pathogen evolution?

Answer 1

it describes how a pathogen does not want to kill its host before the pathogen can replicate and spread to new host

better to be transmissible than cause disease

Question 2

What are the difference between acute, chronic, and latent infections?

Answer 2

Acute: short illness
Chronic: illness persists or recurs over long period
Latent: illness may recur if immunity weakens

Question 3

What are Koch’s posulates?

Answer 3

prove what infectious agent causes a disease
1. Bacterium must be present in every disease case (not healthy ind)
2. Bacterium grown in pure culture
3. Bacterium must cause diseae
4. The bacterium must be recoverable from host

Question 4

How are Koch’s postulates modified in the modern era?

Answer 4

1. gene should be found only in strains of bacteria that cause the disease
2. gene should be “isolated” from cloning
3. disruption of gene in virulent strain should reduce virulence
4. gene is expressed by bacterium during infectious process

Question 5

Infection vs intoxication

Answer 5

Infection: multiplication of organism causes disease
Intoxication: toxin produced by organisms cause disease

Question 6

Role of pathogenicity islands in pathogen evolution

Answer 6

genes for virulence factors are passed between cells as a unit (PAI)

Question 7

How are bacteria able to compete against the hosts adaptive and innate immunity?

Answer 7

1. Penetrate skin
2. Penetrate mucous membranes

Question 8

Role of Microfold (M) cells in MALT tissue within mucous membranes

Answer 8

M cells produce ruffles that take in bacteria and give it to dendritic cells and macrophages in MALT tissue

Question 9

What are three strategies used by pathogens to invade and colonize a host

Answer 9

1. Extracellular: pathogen remains in blood/tissues but not cells
2. Intracellular in circulating cells: lives in macrophages
3. Intracellular in non-circulating cells: lives in epithelial cells

Question 10

What are three way in which bacteria can avoid phagocytosis?

Answer 10

1. activate C5a peptidase-
2. produce leukocidins/lysins
3. thick capsules and special surface protein (black PAMPs)

Question 11

What protein allows Staphylococcus avoid the immune system?

Answer 11

Staphylococcal protein A

Question 12

How do molecular biologists use protein A to aid in ELISA tests

Question 13

How do pathogens use the body’s own proteins to avoid complement activation?

Answer 13

It steals the host’s factor H by producing an alternative factor H binding protein.

Question 14

What are two ways in which some pathogen can avoid the humoral immune system?

Answer 14

Produce IgA protease
Have sialic acid capsule

Question 15

What are three places within phagocytosis where bacteria can sometimes survive

Answer 15

1. break out phagosome, live in cytoplasm
2. prevent phagolysosome, live in phagosome
3. live in phagolysosome

Question 16

Why do some pathogen want to phagocytosed quickly?

Answer 16

less damaging before the macrophage is activated

Question 17

How do bacteria adhere to specific cell types, and how this causes specific infections?

Answer 17

Attach to epithelial cells using pili

Question 18

How do bacteria use Type III secretory systems to get taken into a host cell

Answer 18

deposit effectors into epithelial cells to enhance pathogen binding and uptake (rearrange cytoskeleton to make pedestals)

Question 19

How do intracellular pathogens spread through a tissue?

Answer 19

polymerize host actin cytoskeletal protein (actin “rocket)