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USMLE > Microbiology: Exotoxins > Flashcards

Microbiology: Exotoxins Flashcards

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USMLE® Step 1 flashcards
1
Q

What is the exotoxin for Corynebacterium diphtheriae?

A

Diphtheria toxin: inactivates elongation factor

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2
Q

What is the exotoxin for pseudomonas aeruginosa?

A
  • Exotoxin A: inactivates elongation factor
  • Mechanism: host cell death
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3
Q

Which exotoxins inhibit protein synthesis?

A
  • Diphtheria toxin: corynebacterium diphtheria
  • Exotoxin A: pseudomonas aeruginosa
  • Shiga toxin: Shigella Shiga-like toxin: EHEC
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4
Q

Which exotoxins inactivate elongation factor?

A
  • Diphtheria toxin (corynebacterium diptheriae)
  • Exotoxin A (pseudomonas aeruginosa)
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5
Q

Which exotoxins inactivate the 60s ribosome by removing adenine from RNA?

A

Shiga toxin (Shigella) and shiga like toxin (EHEC)

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6
Q

What is the exotoxin for Shigella?

A

Shiga toxin: inactivates 60s ribosome by removing adenine from rRNA

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7
Q

What is the exotoxin for EHEC?

A

Shiga like toxin: inactivates 60s ribosome by removing adenine from rRNA

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8
Q

Which exotoxins increase fluid secretion?

A
  1. Heat-labile toxin (ETEC): overactivates adenylate Cyclase (increases cAMP) leading to increased Cl- secretion in the gut and H2O efflux
  2. Heat-stable toxin (ETEC): overactivates guanylate cyclase (increases cGMP) leading to decreased resorption of NaCl and H2O in the gut
  3. Anthrax toxin (Bacillus anthracis): mimics adenylate cyclase leading to increased cAMP
  4. Cholera toxin (Vibrio cholerae): overactivates adenylate cyclase (increases cAMP) by permanently activating Gs leading to increased Cl secretion in the gut and H2O efflux
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9
Q

Which exotoxin mimics adenylate cyclase?

A

Anthrax toxin (Bacillus anthracis)

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10
Q

Which toxin overactivates adenylate cyclase and leads to increased chloride secretion in the gut and water efflux?

A

Heat-labile toxin (ETEC)

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11
Q

Which exotoxin overactivates guanylate cyclase leading to decreased resorption of NaCl and H2O in the gut?

A

Heat-stable toxin (ETEC)

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12
Q

Which exotoxin overactivates adenylate cyclase by permanently activating Gs leading to increased secretion in gut and water efflux.

A

Cholera toxin (Vibrio cholera)

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13
Q

Which exotoxin inhibits phagocytic activity?

A

Pertussis toxin (Bordetella pertussis)

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14
Q

Which exotoxin inactivates Gi leading to activation of adenylate cyclase leading to increased cAMP?

A

Pertussis toxin (Bordetella pertussis)

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15
Q

Which exotoxins inhibit release of neurotransmitter?

A
  1. Tetanospasmin (clostridium tetani)
  2. Botulinum toxin (clostridium botulinum)
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16
Q

Which exotoxins are proteases that cleave SNARE (soluble SNF attachment protein receptor), a set of proteins required for neurotransmitter release via vesicular fusion?

A
  1. Tetanospasmin (clostridium tetani)
  2. Botulinum toxin (clostridium botulinum)
17
Q

Which exotoxin is a phospholipase (lecithinase) that degrades tissue and cell membranes?

A

Alpha toxin (clostridium perfringens)

18
Q

Which exotoxin is a protein that degrades the cell membrane?

A

Streptolysin O (Streptococcus pyogenes)

19
Q

What is the mechanism of alpha toxin (clostridium perfringens)?

A

Phospholipase (lecithinase) that degrades tissue and cell membranes

20
Q

What is the mechanism of streptolysin O (streptococcus pyogenes)?

A

Protein that degrades cell membrane

21
Q

Which exotoxins cross-links the beta region of TCR to MHC Class II on APCs outside of the antigen binding site leading to overwhelming release of IL1, IL2, IFN-gamma, and TNF-alpha, leading to shock?

A
  1. Toxic shock syndrome toxin (Staphylococcus aureus) 2. Erythrogenic toxin A (streptococcus pyogenes)
22
Q

What is the mechanism of toxic shock syndrome?

A

cross-links the beta region of TCR to MHC Class II on APCs outside of the antigen binding site leading to overwhelming release of IL1, IL2, IFN-gamma, and TNF-alpha, leading to shock

23
Q

What is the mechanism of erythrogenic toxin (streptococcus pyogenes)?

A

cross-links the beta region of TCR to MHC Class II on APCs outside of the antigen binding site leading to overwhelming release of IL1, IL2, IFN-gamma, and TNF-alpha, leading to shock

24
Q

What is this organism?

A

Histoplasma

  • Presents as patient from the Mississippi-Ohio-Missouri river valleys with calcifying lung lesions
  • Blastomyces also presents this way, but it is a broad-based budding yeast

USMLE (4 decks)

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