Pathogenesis

Question 1

What is Virulence?

Answer 1

the relative ability of a pathogen to cause disease

can be high or low

Question 2

What is Pathogenecity?

Answer 2

the ability to cause disease

can either have or not

no high or low

Question 3

How do you measure Virulence?

Answer 3

use LD₅₀ and/or ID

Question 4

What is ID?

Answer 4

Infectious Dose

of microbes required to cause a set of symptoms

Question 5

What is LD₅₀?

Answer 5

Lethal Dose - 50%

of microbes it takes to kill 50% of the host’s cell population

Question 6

What is a possible course of infection for a extracellular pathogen?

Answer 6

Exposure -> Adherence -> Colonization and Growth -> (Invasion -> Dissemination) or Toxicity -> Tissue Damage/Disease/Transmission

Question 7

What is a possible course of infection for an intracellular pathogen?

Answer 7

Exposure -> Adherence -> (Invasion -> Dissemination) or Toxicity -> Tissue Damage/Disease/Transmission

Question 8

What are the 3 types of Specificity?

Answer 8

Host Specificity

Genetic Specificity

Tissue Specificity

Question 9

What is Adherence to host cells mediated by?

Answer 9

by adhesins

Non-specific = generally sticky (capsule)

Specific = ligand binding

Question 10

How do intracellular pathogens invade host tissues?

Answer 10

they invade directly into host cells

get taken up by vacuoles

manipulate vacuoles do either disintegrate or don’t fuse w/ lysosomes

Question 11

How do extracellular pathogens invade host tissues?

Answer 11

the penetrate in btwn host cells

break the tight junctions and celular cements that bind epithelial layers

Question 12

What are 3 possible mechanisms for intracellular invasion of host cells?

Answer 12

Zipper mechanism

Trigger mechanism

Coiling phagocytosis

Question 13

What is the zipper mechanism?

Answer 13

used for invasion of host cell

bacterium “sinks” into cell

pathogen gives signal to host and host lets it in = gentle

Question 14

What is the Trigger mechanism?

Answer 14

used for invasion into host cell

major rearrangments of host membranes

host bursts open and swallows pahtogen up = brutal

Question 15

What is coiling phagocytosis?

Answer 15

used for invasion of host cell

long coiling psuedopod to come out of host and coil around pahtogen and bring it in

Question 16

What are 4 examples of spreading factors?

Answer 16

Hyaluronidase, Collagenase, Neuraminidase, and Hemolysin

Question 17

What does the spreading factor, Hyaluronidase, do?

Answer 17

attacks the interstitial cement of connective tissue by depolymerizing hyaluronic acid

Question 18

What does the spreading factor, collagenase, do?

Answer 18

breaks down collagen

Question 19

What does the spreading factor, neuraminidase, do?

Answer 19

degrades neuraminic acid and intercellular cement of the epithelial cells of the intestinal mucosa

Question 20

What does the spreading factor, hemolysin, do?

Answer 20

proteins that destroy red blood cells by lysis

forms rings and pokes holes in red blood cells

Question 21

What is Dissemination?

Answer 21

the spreading of pathogens through the body systems (blood, CSF, or lymphatic)

Question 22

What is Endotoxin?

Answer 22

the toxic heat-stable lipopolysaccharide (LPS) present only in the outer membrane of Gram-negative bacteria

released form cell due to shedding or lysis

Question 23

What are the 3 types of Exotoxin?

Answer 23

• Type I = superantigens - staph aureus toxic shock syndrome toxin
• Type II = exotoxins that damage host cell membranes
• Type III = A/B multisubunit toxins that interfere w/ host cel fxn

Question 24

Which pathogen causes chlamydia?

Answer 24

Chlamydia trachomatis

Question 25

What type of pathogen is Chlamydia trachomatis?

Answer 25

obligate intracellular pathogen

Question 26

What are the 2 life forms of Chlamydia trachomatis?

Answer 26

Elementary Body (EB) and Reticulate Body (RB)

Question 27

What is the difference between the EB and the RB of Chlamydia trachomatis?

Answer 27

EB = elementary body = non-replicating infectious article = dispersal form = dormant cell RB = reticulate body = replicating, non infectious = vegetative cell

Question 28

What type of pathogen is Salmonella enterica spp. enterica?

Answer 28

Extracellular, facultative anaerobe, gram negative bacteria

Question 29

What are the virulence factors of Salmonella?

Answer 29

Type II Secretion System that secretes effectors 2 Type III Secretion Systems = one for entering host cell, one for escaping vacuole

Question 30

What are the steps that Salmonella takes to invade host cells?

Answer 30

1. salmonella adheres to host cell wall 2. salmonella uses Type III secretion system to inject host cell and inject effectors * causes host cel to engulf salmonella into vacuole (SCV) 3. salmonella prevents lysosome binding to vacuole using Type III secretion system 4. salmonella then begins replicating and eventually escapes vacuole and spreads