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Microbiology > Bacterial Exotoxins > Flashcards

Bacterial Exotoxins Flashcards

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Biology 101 flashcards
1
Q

ADP ribosylating A-B toxin MOA

A

B (binding) component binds to host cell surface receptor, enabling endocytosis.
A (active) component attaches ADP-ribosyl to disrupt host cell proteins.

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2
Q

Corynebacterium diphtheriae (inhibit protein synthesis)

  1. Toxin
  2. Mechanism
  3. Manifestation
A
  1. Diphtheria toxin
  2. Toxin is an ADP ribosylating A-B toxin; Inactivates elongation factor (EF-2)
  3. Pharyngitis with pseudomembranes in throat and severe lymphadenopathy (bull neck)
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3
Q

Pseudomonas aeruginosa (inhibit protein synthesis)

  1. Toxin
  2. Mechanism
  3. Manifestation
A
  1. Exotoxin A
  2. Toxin is an ADP ribosylating A-B toxin; Inactivates elongation factor (EF-2)
  3. Host cell death
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4
Q

Shigella spp. (inhibit protein synthesis)

  1. Toxin
  2. Mechanism
  3. Manifestation
A
  1. Shiga toxin (ST)
  2. Inactivate 60S ribosome by removing adenine from rRNA
  3. GI mucosal damage –> dysentery; ST also enhances cytokine release, causing HUS
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5
Q

Enterohemorrhagic E. coli (EHEC), including O157:H7 strain (inhibit protein synthesis)

  1. Toxin
  2. Mechanism
  3. Manifestation
A
  1. Shiga-like toxin (SLT)
  2. Inactivate 60S ribosome by removing adenine from rRNA
  3. SLT enhances cytokine release, causing HUS; unlike Shigella, EHEC does not invade host cells
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6
Q

Enterotoxigenic E. coli (ETEC) (increase fluid secretion)

  1. Toxin (x2)
  2. Mechanism (x2)
  3. Manifestation (x2)
A
  1. Heat-labile toxin (LT)
  2. Toxin is an ADP ribosylating A-B toxin; Overactivates adenylate cyclase (increases cAMP) –> increased Cl- secretion in gut and H2O efflux
  3. Watery diarrhea (labile in the Air; Adenylate cyclase)
  4. Heat-stable toxin (ST)
  5. Overactivates guanylate cyclase (increases cGMP) –> decreased resorption of NaCl and H2O in the gut
  6. Watery diarrhea (stable on the Ground; Guanylate cyclase)
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7
Q

Bacillus anthracis (increase fluid secretion)

  1. Toxin
  2. Mechanism
  3. Manifestation
A
  1. Edema factor
  2. Mimics the adenylate cyclase enzyme (increases cAMP)
  3. Likely responsible for characteristic edematous borders of black eschar in cutaneous anthrax
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8
Q

Vibrio cholerae (increase fluid secretion)

  1. Toxin
  2. Mechanism
  3. Manifestation
A
  1. Cholera toxin
  2. Toxin is an ADP ribosylating A-B toxin; Overactivates adenylate cyclase (increases cAMP) by permanently activating Gs –> increased Cl- secretion in gut and H2O efflux
  3. Voluminous “rice-water” diarrhea
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9
Q

Bordetella pertussis (inhibit phagocytic ability)

  1. Toxin
  2. Mechanism
  3. Manifestation
A
  1. Pertussis toxin
  2. Toxin is an ADP ribosylating A-B toxin; Overactivates adenylate cyclase (increases cAMP) by disabling Gi, impairing phagocytosis to permit survival of microbe
  3. Whooping cough: child coughs on expiration and “whoops” on inspiration (toxin may not actually be a cause of cough; can cause “100-day cough” in adults)
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10
Q

Clostridium tetani (inhibit release of neurotransmitter)

  1. Toxin
  2. Mechanism
  3. Manifestation
A
  1. Tetanospasmin
  2. Cleave SNARE protein required for neurotransmitter release
  3. Muscle rigidity and “lock jaw”; toxin prevents release of inhibitory (GABA and glycine) neurotransmitters in the spinal cord
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11
Q

Clostridium botulinum (inhibit release of neurotransmitter)

  1. Toxin
  2. Mechanism
  3. Manifestation
A
  1. Botulinum toxin
  2. Cleave SNARE protein required for neurotransmitter release
  3. Flaccid paralysis, floppy baby; toxin prevents release of stimulatory (ACh) signals at neuromuscular junctions –> flaccid paralysis
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12
Q

Clostridium perfringens (lyse cell membranes)

  1. Toxin
  2. Mechanism
  3. Manifestation
A
  1. Alpha toxin
  2. Phospholipase that degrades tissue and cell membranes
  3. Degradation of phospholipid C –> myonecrosis (“gas gangrene”) and hemolysis (“double zone” of hemolysis on blood agar)
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13
Q

Streptococcus pyogenes (lyse cell membranes)

  1. Toxin
  2. Mechanism
  3. Manifestation
A
  1. Streptolysin O
  2. Protein that degrades cell membrane
  3. Lyses RBCs; contributes to B-hemolysis; host antibodies against toxin (ASO) used to diagnose rheumatic fever (do not confuse with immune complexes of poststreptococcal glomerulonephritis)
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14
Q

Staphylococcus aureus (superantigen causing shock)

  1. Toxin
  2. Mechanism
  3. Manifestation
A
  1. Toxic shock syndrome toxin (TSST-1)
  2. Bring MHC II and TCR in proximity to outside of antigen binding site to cause overwhelming release of IFN-g and IL-2 –> shock
  3. Toxic shock syndrome: fever, rash, shock; other toxins cause scalded skin syndrome (exfoliative toxin) and food poisoning (enterotoxin)
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15
Q

Streptococcus pyogenes (superantigen causing shock)

  1. Toxin
  2. Mechanism
  3. Manifestation
A
  1. Exotoxin A
  2. Bring MHC II and TCR in proximity to outside of antigen binding site to cause overwhelming release of IFN-g and IL-2 –> shock
  3. Toxic shock syndrome: fever, rash, shock
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