Test 1: lecture 3: Pathogenic Mechanism

Question 1

Koch’s postulates

1. must be found in organisms with disease, and not in ___
2. must be isolated and grown ___
3. cultured bug will ___ if introduced into a healthy organism
4. bug must be re-isolated from the inoculated, diseased experimental host and be ____

Answer 1

healthy organism

in culture

cause disease

identical to original bug

Question 2

what type of bacteria work for Koch Postulates?

Answer 2

plaque and anthrax

(not found on healthy person)

Question 3

what is wrong about Koch Postulates?

Answer 3

microbes can be found on healthy hosts and not cause disease

example: staph

Question 4

Molecular koch’s postulates

1. The phenotype or property should be assoc. w/ pathogenic members of a genus or pathogenic strains of a species. ____ in question present in all pathogenic species but absent from nonpathogenic species.
2. Specific ___ of gene(s) assoc. w/ virulence trait should lead to measurable loss in virulence – demonstrated in animal model.
3. ___ of mutated gene should lead to restoration of pathogenicity.
4. The gene, which causes virulence, must be ___ during infection
5. Caveats – culturability, availability of genetics, animal model

Answer 4

Gene

inactivation

Reversion or allelic replacement

expressed

Question 5

indigenous microbiota also called ___

Answer 5

commensal flora

Question 6

Pathogens possess the inherent ability to___ that limit the survival or replication of other microbes and commensals.

Answer 6

cross anatomic barriers or breach other host defenses

Question 7

most pathogens can establish themselves in a___ usually devoid of other stable microbial populations.

Answer 7

niche

Question 8

pathogen vs commensal bacteria?

Answer 8

pathogens will invade and breach host defenses

will establish a niche to live in that host can not defend

host specific

Question 9

___ cause disease only in compromised human hosts

Answer 9

opportunistic pathogens

Question 10

some microbes are commonly found in normal flora but also cause human disease such us ___

Answer 10

Question 11

what are some virulence determinants of commensal pathogens that allow them to survive

Answer 11

capsule

IgA protease→ cut off flag that tells host it is there

pili

anti-phagocytic proteins

Question 12

what kind of barriers does skin have?

Answer 12

Question 13

what kind of barriers does the gut have?

Answer 13

Question 14

what kind of barriers does the lungs have?

Answer 14

Question 15

what kind of barriers does the eye/nose have?

Answer 15

Question 16

steps in infection

Answer 16

1) Entry into host
2) Attainment of unique niche- specific means of assoc./attachment
3) Evade, subvert or circumvent initial host defense mechanisms
4) Multiplication or persistence
5) Disease- as an option; overt clinical disease is usually not the outcome
6) Exit/Transmission

Question 17

steps in infection

1) Entry into ___
2) Attainment of unique ___- specific means of assoc./attachment
3) Evade, subvert or circumvent ___ mechanisms
4) Multiplication or persistence
5) ___- as an option; overt clinical disease is usually not the outcome
6) ___

Answer 17

host

niche

initial host defense

Disease

Exit/Transmission

Question 18

how does Y. pestis avoid detection

Answer 18

forms WT LPS that evades TLR4. ends up killing the host

Question 19

how does salmonella invade

Answer 19

forms type 3 secretion system (T3SS)

“needle” causes cell to ruffle and eat the salmonella virus

will invade macrophages, turn off eating ability and use the macrophage like an uber

encoded on salmonella pathogenicity island that is a block of genes that encode fro T3SS

Question 20

why does salmonella invade macrophages

Answer 20

uses it to travel

Question 21

why would a microbe invade a host cell

Answer 21

escape immune surveillance
– obtain nutrients by parasitizing host cell machinery
– transportation!

Question 22

2 ways pathogens invade a host cell

Answer 22

zipper

trigger (needle → ruffle → eat the pathogen)

Question 23

what kind of pathogens will escape from the vacuole once they are in the host cell

Answer 23

Listeria
• Shigella
• Rickettsia
• Francisella (no actin-based motility)

move around by moving on the actin → actin tails

Question 24

what pathogens will modify the vacuole of the host cell

Answer 24

Salmonella – Mycobacterium – Chlamydia – Legionella pneumophila