Mechanisms of infection :) Flashcards

1
Q

what are pathogens

A

disease causing organisms that are fully virulent

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2
Q

what do pathgens show

A

clonality
reproduction -asexual
each cell has a similar capability

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3
Q

what are opportunistic pathogens

A

possess soem virulence factors

often commensals

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4
Q

aim of pathgen

A

reproduction and maintenance of its genes in envrionemtn

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5
Q

what are seroconverts

A

those who can make antibodies agains the pathogens

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6
Q

routes of transmission

A
aerosols
foetal oral spread
venereal spread
vector vertebrate reservoir
vector vertebae
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7
Q

vertical transmission

A

between generations e.g. through placenta

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8
Q

what is an infectious dose

A

have to have enough bacteria that will survive to infect

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9
Q

requirement for infection

A

adhere to susceptible cell
grow in/on host
evade host defenses

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10
Q

examples of bacterial appendages

A

pilli

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11
Q

what are bacterial capsules made of

A

polysaccharides

bind to artificial surfaces and tooth pellicles (important in biofilm formation)

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12
Q

what can bacteria bind to

A

surface proteins/glycoprotiens

e.g. HIV binds to CD4

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13
Q

biofilm formation

A

primary colonisation of surface

secondary colonisation by extracellular polysaccharide and cell interactions

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14
Q

what are the gradients within the plaque community

A

towards edge more active

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15
Q

what can aid colonisation

A

motility i.e. flagellum

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16
Q

what can flagellum help with

A

penetrate mucous blanket
penetrate intercellular junctions
colonisation of catheters

17
Q

formation of pedestals

A

1) Bacteria sticks to cell
2) retracts the cells
3) needles stick out
4) send proteins out through the needles
5) form a hole to send more proteins
6) proteins sit in the membrane
7) Then the bacteria can sit in the membrane
8) Sends in more protein, causes actin polymerisation (cytoskeleton)
9) Pellicle is formed

18
Q

how can bacteria manituplate the host

A

manipulate the endocytosis system of cells
bind receptors using pili
pedestal formed in intestinal brush border
then inject cell effectors using section needles

19
Q

invasion of cell steps

A

1) Attaches
2) Sends needle inside cytoskeleton
3) Uses the vesicle to go inside
4) pH changes
5) triggers organism to send out another needle
6) Manipulates vesicle to make home for itself
7) Then divides

20
Q

summary of colonisation

A
  • Transmission by aerosol, direct contact, wound/infect
  • Attachment by fimbriae, polysaccharide, protein adhesion
  • Motility aids colonisation
  • Invade by subversion of endocytosis system
21
Q

complement involved in invasion

A

deposits on surface
become activated by antigens
makes membrane attack complement
bacterial cell then burst

22
Q

evasion of complemtn

A

gram -
LPS forms a brush border preventing proteins getting to the cell membrane
gram +
capsules able to stop deposition on surface of the cell

23
Q

normal IgA fuction

A
non complement activated cell
M cell detects pathogen
- T cell and B cell activation to make IgA colecuels
IgA molecules are then sent out
protect from adhesion

soem bacteria are able to chop up IgA

24
Q

subverting phagocytosis

A
toxis
evade phagocytosis (capsule exclusion)
avoid killing within a phagosome
25
how do toxins evade defences
toxins can target leucoidins | kills phagocytes
26
how can you avoid killing within a phagosome
escape from phagosome resist lytic enzymes inhibit generation of superoxide or degrafde them
27
what does tuberculosis do
evades killing surpasses immune responcec multiplies in macrophages
28
subverting t cells
incapacitate t cells | - infects and destroys CD4 and T cells
29
secret agent methods of evasion
``` surface antigen variation molecular mimicry infection of privleged sites decoys:smokescreens degrade or inhibit complement ```
30
surface antigen variation
change antigens to evade immune system
31
molecular mimicry
coat with host protein | incorporation of silica acid into LPS on surface
32
infection of privileged sites
not easily detected in areas with less immune cells
33
decoys/smokescreen
bacteria may send out false messages | bind to antibodies/antigens to occupying them to give more time to run away
34
degraded inhibit complement
intercept codes and misinformation | give more time for colonisation, adhesion or infection
35
force fields
organisms produce urease acts as protective cloud during transit to gastric mucin layer take the urea and chop it up into amminoia and CO2