Test 1: lecture 3: Pathogenic Mechanism Flashcards
Koch’s postulates
- must be found in organisms with disease, and not in ___
- must be isolated and grown ___
- cultured bug will ___ if introduced into a healthy organism
- bug must be re-isolated from the inoculated, diseased experimental host and be ____
healthy organism
in culture
cause disease
identical to original bug
what type of bacteria work for Koch Postulates?
plaque and anthrax
(not found on healthy person)
what is wrong about Koch Postulates?
microbes can be found on healthy hosts and not cause disease
example: staph
Molecular koch’s postulates
- 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.
- Specific ___ of gene(s) assoc. w/ virulence trait should lead to measurable loss in virulence – demonstrated in animal model.
- ___ of mutated gene should lead to restoration of pathogenicity.
- The gene, which causes virulence, must be ___ during infection
- Caveats – culturability, availability of genetics, animal model
Gene
inactivation
Reversion or allelic replacement
expressed
indigenous microbiota also called ___
commensal flora
Pathogens possess the inherent ability to___ that limit the survival or replication of other microbes and commensals.
cross anatomic barriers or breach other host defenses
most pathogens can establish themselves in a___ usually devoid of other stable microbial populations.
niche
pathogen vs commensal bacteria?
pathogens will invade and breach host defenses
will establish a niche to live in that host can not defend
host specific
___ cause disease only in compromised human hosts
opportunistic pathogens
some microbes are commonly found in normal flora but also cause human disease such us ___
what are some virulence determinants of commensal pathogens that allow them to survive
capsule
IgA protease→ cut off flag that tells host it is there
pili
anti-phagocytic proteins
what kind of barriers does skin have?
what kind of barriers does the gut have?
what kind of barriers does the lungs have?
what kind of barriers does the eye/nose have?
steps in infection
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
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) ___
host
niche
initial host defense
Disease
Exit/Transmission
how does Y. pestis avoid detection
forms WT LPS that evades TLR4. ends up killing the host
how does salmonella invade
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
why does salmonella invade macrophages
uses it to travel
why would a microbe invade a host cell
escape immune surveillance
– obtain nutrients by parasitizing host cell machinery
– transportation!
2 ways pathogens invade a host cell
zipper
trigger (needle → ruffle → eat the pathogen)
what kind of pathogens will escape from the vacuole once they are in the host cell
Listeria
• Shigella
• Rickettsia
• Francisella (no actin-based motility)
move around by moving on the actin → actin tails
what pathogens will modify the vacuole of the host cell
Salmonella – Mycobacterium – Chlamydia – Legionella pneumophila
