Major Exotoxins

Question 1

Exotoxin A

1. organism, gram +/-
2. role
3. MOA
4. 1’ target

Answer 1

1. pseudomonas aeruginosa, gram -
2. inhibits eukaryotic cell protein synthesis
3. MOA: ADP ribosyl transferase; inactivates eEF-2 –> inhibiting elongation
4. 1’ targets: liver

Question 2

Shiga toxin

1. organism, gram +/-
2. role
3. MOA
4. 1’ target

Answer 2

1. shigella dysenteriae, gram -
2. inhibits eukaryotic cell protein synthesis;
   - enterotoxic, cytotoxic, and neurotoxic
3. MOA: interferes with 60S ribosomal subunit

Question 3

Diphtheria toxin

1. organism, gram +/-
2. role
3. MOA
4. 1’ target

Answer 3

1. corynebacterium diphtheriae, gram +
2. inhibits eukaryotic cell protein synthesis
3. MOA: ADP ribosyl transferase; inactivates eEF-2 –> inhibiting elongation
4. 1’ targets: heart, nerves, epithelium

Question 4

verotoxin

1. organism, gram +/-
2. role
3. MOA

Answer 4

• verotoxin = a shiga-like toxin
  1. enterohemorrhagic E. coli (EHEC), gram -
  2. inhibits eukaryotic cell protein synthesis
  3. MOA: interferes with 60S ribosomal subunit

Question 5

tetanus toxin

1. organism, gram +/-
2. role
3. MOA

Answer 5

1. clostridium tetani, gram +
2. Neurotoxin: inhibits neurotransmission in inhibitory synapses
3. MOA: blocks release of the inhibitory transmitters GABA and Glycine

Question 6

botulinum toxin

1. organism, gram +/-
2. role
3. MOA

Answer 6

1. clostridium botulinum, gram +
2. Neurotoxin: inhibits cholinergic synapses
3. MOA: blocks release of ACh

Question 7

TSST-1

1. organism, gram +/-
2. role
3. MOA

Answer 7

1. staphylococcus aureus, gram +
2. fever, increased susceptibility to LPS, rash, shock, capillary leakage
3. MOA: superantigen = overstimulates immune system via T cells –> cytokine storm

Question 8

Exotoxin A

1. organism, gram +/-
2. role
3. MOA

Answer 8

• aka erythrogenic or pyrogenic toxin
  1. streptococcus pyogenes, gram +
  2. fever, increased susceptibility to LPS, rash, shock, capillary leakage, cardiotoxicity
  3. similar to TSST-1; superantigen = overstimulates immune system via T cells –> cytokine storm

Question 9

Heat labile toxin (LT)

1. organism, gram +/-
2. role
3. MOA

Answer 9

1. enterotoxigenic E. coli, gram -
2. both LT and ST promote secretion of fluid and electrolytes from intestinal epithelium
3. LT stimulates and an Adenylate Cyclase by ADP ribosylation of GTP binding protein –> massive amounts of watery diarrhea

Question 10

cholera toxin

1. organism, gram +/-
2. role
3. MOA

Answer 10

1. vibrio cholerae, gram -
2. profuse, watery diarrhea
3. similar to E. coli LT (LT stimulates and an Adenylate Cyclase by ADP ribosylation of GTP binding protein –> promote secretion of fluid and electrolytes from intestinal epithelium)

Question 11

Anthrax Toxin (3 proteins make 2 toxins)

1. organism, gram +/-
2. role
3. MOA

Answer 11

1. bacillus anthracis, gram +
2. decreases phagocytosis; causes edema, kills cells
3. EF = edema factor = adenylate cyclase
   - LF = lethal factor
   - PA = protective antigen (B component for both)

Question 12

Pertussis toxin

1. organism, gram +/-
2. role
3. MOA

Answer 12

1. bordetella pertussis, gram -
2. cAMP inducer: histamine-sensitizing lymphocytosis promoting islet activating
3. ADP ribosylates Gi (the negative regulator of adenylate cyclase) –> increased cAMP

Question 13

Clostridium perfringens

1. gram +/-?
2. toxin
3. role
4. MOA

Answer 13

1. gram +
2. alpha toxin
3. damages cell membranes –> myonecrosis
4. lecithinase ( = cytolysin)

Question 14

staphylococcus aureus

1. gram +/-?
2. toxin
3. role
4. MOA

Answer 14

1. gram +
2. alpha toxin
3. cell membrane becomes leaky
4. toxin intercalates forming pores