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MCR101 > Topic 11 - Mechanisms of Pathogenicity > Flashcards

Topic 11 - Mechanisms of Pathogenicity Flashcards

1
Q

What are the four hurdles pathogens must over come to cause disease?

A
  1. Gain access to host through portals of entry
  2. Must adhere to host tissues
  3. Must penetrate or evade host defences
  4. Must damage host tissues
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2
Q

List the principal portals of entry

A 
Mucous membranes (genitourinary tract, respiratory tract, gastrointestinal tract)
Skin
Parental route (punctures, bites,cuts etc)
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3
Q

List the requirements for infection

A 
1. Gain access to host
2 Establish and increase in numbers
3.Evade the host immune system
4. Destroy/damage host tissues
5. Exit and survive to infect another host
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4
Q

LOOK AT DIAGRAM LINKING MECHANISMS OF PATHOGENICITY

A

DO IT SHITHEAD. AND WRITE IT OUT.

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5
Q

A bit about the parental route…?

A

Bypasses the stomach e.g. if the stomach’s natural acid destroy a drug, it needs to go another way to get into the body e.g. injection, cut, puncture

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6
Q

What is ID50?

A

Infectious dose for 50% of the test population

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7
Q

What is LD50?

A

Lethal dose (of a toxin) for 50% of the test population

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8
Q

The lower the LD50, the more…?

A

virulent the pathogen is

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9
Q

More virulent = low…?

A

ID50 and LD50

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10
Q

Less virulent = high..?.

A

ID50 and LD50

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11
Q

All pathogens have a means of attaching to host tissues after gaining entry, which is called…?

A

adherence

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12
Q

List two Adhesins/ligands. What do they bind to? And what do they form?

A
  1. Glycocalyx (helps form capsule)
  2. Fimbriae (thin filaments)
    Bind to receptors on host cells.
    Form bioflms.
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13
Q

How does M protein contribute to pathogenicity? (cell wall component)

A

Mediates attachment of the bacterium to cells of the host and helps bacterium resist phagocytosis by WBC’s

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14
Q

How does Opa protein contribute to pathogenicity? (cell wall component)

A

Helps bacterium attach to host cells cell

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15
Q

How does Mycolic acid contribute to pathogenicity? (cell wall component)

A

Resists digestion

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16
Q

How do bacterial capsules contribute to pathogenicity?

A

Prevent phagocytosis -capsule is slippery and our immune cells cannot catch them.

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17
Q

Bacterial capsules are …… defence

A

passive

18
Q

Bacterial enzymes are …. defence

A

active

19
Q

How does the bacterial enzyme Coagulase evade host immune system?

A

Coagulates fibrinogen. (fibrinogen is a proten produced by liver which helps stop bleeding by helping blood clots).

20
Q

How does the bacterial enzyme Kinase evade host immune system?

A

Digests fibrin clots

21
Q

How does the bacterial enzyme Hyaluronidase evade host immune system?

A

Hydrolyses hyaluronic acid

22
Q

How does the bacterial enzyme Collagenase evade host immune system?

A

Hydrolyses collagen

23
Q

How does the bacterial enzyme IgA protease evade host immune system?

A

Destroy IgA antibodies

24
Q

What is antigenic variation?

A

Some microbes vary expression of surface proteins, thus avoiding the host’s antibodies

25
Q

How does a bacteria use the host cell’s cytoskeleton to enter the cell?

A

Invasins - alters host actin and uses it to move from one cell to the next

26
Q

Give 3 examples of direct damage?

A
  1. Disrupt host cell function
  2. Produce waste products
  3. Toxins
27
Q

What is a toxin?

A

Poisonous substances produced by bacteria

28
Q

What is toxigenicity?

A

Ability to produce a toxin

29
Q

What is toxemia?

A

Presence of toxin in the host’s blood

30
Q

What is a toxoid?

A

Inactivated toxin used in a vaccine

31
Q

What is an antitoxin?

A

Antibodies against a specific toxin

32
Q

What is an exotoxin? A bit about them?

A

PROTEINS PRODUCED INSIDE PATHOGENIC BACTERIA and released into surrounding medium
Antibodies produced against them are called antitoxins
Specific for a structure or function in host cell

33
Q

List the different types of exotoxins and what they do

A

membrane disrupting toxins - Lyse host cells by making channels in plasma membrane (leukocidins, hemolysins, streptolysins)

A-B toxins - Made up of two polpeptides: active enzyme (A) and a binding component (B)

Superantigens - Provoke intense non-specific immune reaction by causing T cells to produce large amounts of cytokines

34
Q

What is an endotoxin? A bit about them?

A

LIPID PORTION (LIPID A) OF THE LIPOPOLYSACCHERIDES IN OUTER MEMBRANE OF GRAM -VE CELL WALL BACTERIA
Released when gram -ve bacteria die and cells lyse
Cause:
Fever, inflammation, respiratory distress, decreased cardiac output etc

35
Q

Compare exotoxins and endotoxins

A

Source: gram -ve (endo), gram +ve (exo)
Relation to microbe: outer membrane (endo), by-products of growing cell (exo)
Chemistry: Lipid A (endo), Protein (exo)
Fever?: yes (endo), no (exo)
Neutralised by antitoxin?: no (endo), yes (exo)
LD50: large (endo), small (exo)

36
Q

What is the LAL assay?

A

Limulus Amoebocyte Lysate assay for detection of endotoxins.

37
Q

How does the LAl assay work?

A

Uses WBC’s from horse shoe crab, which differ from human WBC’s so when mixed with endotoxins form a cloudy substance (very turbid).
The degree of turbidity is a measure of endotoxin contamination

38
Q

List 9 cytopathic effects of viruses

A
  1. Halt macromolecular synthesis in host cell
  2. Cause host cell to release lysosome contents
  3. Cause inclusion bodies to form in host cell
  4. Fusion of infected cells to form a syncitium
  5. Changes in host cell function
  6. Induce host cells to produce interferons
  7. Cause antigenic changes on host cell surface
  8. Induce chromosomal changes in host cell
  9. Loss of contact inhibition in host cells
39
Q

What is an interferon?

A

Proteins made & released by host cells in response to the presence of pathogens e.g. viruses, parasites, bacteria

40
Q

What are the pathogenic properties of fungi?

A
  1. fungal waste products cause symptoms
  2. Chronic infections provoke allergic response
  3. Toxin production
  4. Proteases (candida)
  5. Capsule prevents phagocytosis
41
Q

List the portals of exit?

A
  1. Respiratory tract
  2. Gastrointestinal tract
  3. Genitourinary tract
  4. Skin
  5. Blood

MCR101 (13 decks)

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