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UVic BIOL 459 amy > Final > Molecular Basis of Infection > Flashcards

Final > Molecular Basis of Infection Flashcards

1
Q

Define pathogenicity.

A

The ability to cause disease.

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2
Q

Define virulence.

A

The degree of pathogenicity (ability to cause disease).

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3
Q

What are the 3 main portals of entry for microorganisms to enter a host?

A
  1. Mucous membranes
  2. Skin
  3. Parenteral route (cut)
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4
Q

What is meant by ID₅₀?

A

A measure of the infectious dose necessary to infect 50% of the population. (virulence)

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5
Q

What is meant by LD₅₀?

A

A measure of the lethal dose necessary to kill 50% of the population. (potency)

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6
Q

What can have an effect on the ID₅₀ of a microorganism?

A

Environmental/chemical factors. Ex: lime increases the infectivity of Cryptosporidium parvum.

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7
Q

By what process do pathogens attach to host tissues?

A

By adherence (adhesion), where adhesins (ligands) on the pathogen bind to receptors on the host cell.

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8
Q

What is a glycocalyx?

A

A carbohydrate coating on the outside of many bacteria.

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9
Q

What is the function of M protein on the surface of a microorganism?

A

To resist phagocytosis by the host immune system.

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10
Q

What is the function of OPA protein on the surface of a microorganism?

A

To allow attachment to the host cells.

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11
Q

What is the function of waxy lipid (mycolic acid) on the surface of a microorganism?

A

To resist digestion.

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12
Q

How can antigenic variation help microorganisms survive in the host?

A

The microorganism alters its surface antigens, rendering antibodies ineffective.

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13
Q

What is the purpose of an invasin? In what 2 ways can it help a microorganism

A

A bacterial surface protein

  1. Rearranges actin cytoskeleton to allow entry into host
  2. Rearranges actin to allow transmission to new hosts
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14
Q

What is a siderophore?

A

A protein secreted by a pathogen which can bind iron more tightly than the host cell can, making it available for the pathogen.

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15
Q

What part of the antigen does IgA target? What is characteristic of this region?

A

Targets the middle region of the antigen which is rich in proline.

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16
Q

What is an example of a bacterial siderophore?

A

Enterobactin.

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17
Q

In what 4 main ways can pathogens cause direct damage to a host cell?

A
  1. Disrupt host cell function
  2. Use up host cell nutrients
  3. Produce waste products
  4. Multiply and lyse host cell
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18
Q

Define toxigenicity.

A

The ability of a microorganism to produce a toxin.

19
Q

What is an exotoxin?

A

A protein produced and secreted by bacteria that is soluble in body fluids and has harmful effects.

20
Q

What are 2 examples of inactivated exotoxins that are used in vaccines?

A
  1. Diptheriae vaccine

2. Tetanus vaccine

21
Q

Describe the 2 components of A-B toxins.

A
  1. A = enzyme component

2. B = binding component

22
Q

What are some examples of A-B toxins?

A

Diptheria toxin, Pertussis toxin, Tetanus toxin, Botulin, Cholera toxin, etc.

23
Q

What 4 steps outline A-B toxin function?

A
  1. Bacteria releases toxin
  2. B component binds to host cell
  3. Endocytosis of toxin
  4. A component released into cytoplasm, alters function
24
Q

What is the function of a membrane-disrupting toxin?

A

To disrupt the host plasma membrane, resulting in lysis.

25
Q

What is a leukocidin?

A

An exotoxin which kills phagocytic leukocytes.

26
Q

What is a hemolysin?

A

An exotoxin which kills erythrocytes by forming protein channels.

27
Q

What is a streptolysin?

A

A hemolysin produced by streptococci.

28
Q

What is a superantigen?

A

An exotoxin which releases cytokines from host cells, causing an intense immune response.

29
Q

What is a genotoxin?

A

An exotoxin which damages DNA by causing mutations, potentially disrupting cell division and leading to cancer.

30
Q

What is the main structural difference between exotoxins and endotoxins?

A

Exo: protein-based
Endo: lipid-based

31
Q

What type of bacteria most commonly release endotoxins? When do they do this?

A

Gram negative bacteria release them during replication and cell death (from membrane).

32
Q

How do endotoxins act on host cells? What deadly symptom can result?

A

Stimulate macrophages to release cytokines. Can cause disseminated intravascular coagulation.

33
Q

What assay is used to test for endotoxins? How does it work?

A

Limulus amebocyte lysate (LAL) assay. In the presence of endotoxins the amebocytes lyse and produce a clot.

34
Q

What type of bacteria most commonly release exotoxins?

A

Gram positive bacteria.

35
Q

In general, how do the effects of exotoxins differ from those of endotoxins?

A

Exo: specific effect
Endo: generalized effect

36
Q

Which type of toxin (endo or exo) is most stable in heat?

A

Endotoxins. They can even withstand autoclaving! Crazy!

37
Q

What does “lysogenic conversion” mean?

A

A change in the characteristics of a microbe due to the incorporation of a prophage.

38
Q

What is meant by “cytopathic effects” (CPE)?

A

The visible effects of viral infection on a cell.

39
Q

What are some examples of cytopathic effects?

A
  • Cell synthesis stops
  • Lysosomes release enzymes
  • Fusing multiple cells
  • Changing host function
  • Chromosomal changes
  • Inducing surface antigens
  • Loss of contact inhibition
  • Production of interferons
40
Q

What is a syncytium?

A

A single cell or cytoplasmic mass containing several nuclei, formed by fusion of cells or by division of nuclei.

41
Q

What is an inclusion body in terms of cell anatomy? What are they indicative of?

A

Protein aggregates in the cytosol or nucleus. Indicate sites of viral replication.

42
Q

Who was the first to show that Rous sarcoma ( a type of fibroblast cancer) was caused by a retrovirus? When?

A

Howard Temin in 1960 (retrovirus = RNA virus with a DNA stage)

43
Q

What are the 5 main portals of exit for microorganisms to leave a host?

A
  1. Respiratory tract (ex: cough)
  2. Gastrointestinal tract (ex: spit or shit)
  3. Genitourinary tract (ex: pee + other fluids)
  4. Skin (sweat?)
  5. Blood (ex: bug bites)

UVic BIOL 459 amy (16 decks)

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