Micro 2 - Bacterial Toxins

Question 1

What does endotoxin affect in the body?

Answer 1

Macrophages, complement system and tissue factor liberation.

Question 2

What are exotoxins?

Answer 2

Proteins produced by bacteria and then released. They are usually released by G(+) bacteria that have plasmids or are bacteriophages that encode for these exotoxins. Also, exotoxins are antigenic: you can develop antibodies against them (ie: tetanus and diptheria vaccines are toxid vaccines).

Question 3

What do neurotoxins do and what are two examples of them?

Answer 3

They interfere with neural transmission.

1. Botulinum toxin.
2. Tetanus toxin.

Question 4

What do enterotoxins do and what are some examples of them?

Answer 4

They affect the intestines.

1. Shigella.
2. Vibrio cholera.

Question 5

What are superantigens?

Answer 5

Exotoxins able to bind to MHC class II receptor and TCR (T cell receptor) simultaneously, causing polyclonal expansion of T cells, causing a massive immune response and release of large amounts of cytokines.

Question 6

What are the two best know bacteria to release Superantigens?

Answer 6

1. Staphylococcus aureus.

2. Streptococcus pyogenes.

Question 7

What known toxins are secreted by Staph aureus and what are the actions of each?

Answer 7

1. Alpha-toxin: hemolysis.
2. Beta-toxin: sphingomyelinase.
3. Proteins A, B, and C, of gama-toxin (Y): A+B= hemolysin, B+C= leukocidin.
4. Delta hemolysin: hemolysis.
5. Panton-Valentine leukocidin: destroys leukocytes.

Question 8

What are the three superantigens produced by Staph auereus?

Answer 8

1. Enterotoxins A-E: from food poisoning, causing vomiting and diarrhea.
2. TSST-1: causes release of cytokines, causing toxic shock syndrome.
3. Epidermolytic/exfoliative toxin: causes epithelial cell lysis, causing scalded skin syndrome.

Question 9

What are the symptoms of Toxic shock syndrome?

Answer 9

High fever, hypotension and a diffuse rash that looks like a sunburn.

Question 10

What known toxins are secreted by Streptococcus pyogenes (group A strep)? What is the action of each?

Answer 10

1. Streptolysin O: hemolysis (Oxygen labile). We use antibodies against this toxin to detect if a person has had a recent infection with group A Strep (ASO titers).
2. Streptolysin S: hemolysis (Oxygen Stable).
3. Erythrogenic/ pyrogenic toxins: Skin rash (erythro-) and fever (pyro-) of scarlet fever. They act as superantigens.

Question 11

What does the diptheria toxin produced by the Corynebacterium diphtheriae do?

Answer 11

It inactivates EF-2 (elongation factor 2), which inhibits protein synthesis. It causes pharyngitis w/ gray pseudomembranes. Cardiac and nerve cells are particularly vulnerable to this toxin.

Question 12

What are the exotoxin produced by the Pseudomonas aeruginosa and what do they do?

Answer 12

Exotoxin A: targets EF-2.

Question 13

What are the exotoxin produced by the Shigella and what do they do?

Answer 13

Shiga toxin: It cleaves host rRNA at adenine base in 60s ribosomal subunit. It causes inhibition of protein synthesis, leading to cell death.

Question 14

What are the exotoxin produced by the toxin-producing E. coli and what do they do?

Answer 14

1. Entero hemorrhagic E. coli (EHEC):
   - O157:H7
   - Verocytotoxin (Shiga-like toxin): causes bloody diarrhea and damge to renal and endothelial cells causing Hemolytic Urymic syndrome.
2. Enterotoxigenic E. coli (ETEC):
   - Heat labile toxin: causes increase in cAMP.
   - Heat stable toxin: causes increase in cGMP.
   (This is the leading cause of traveler’s diarrhea).

Question 15

What are the symptoms of Hemolytic-uremic syndrome (HUS)?

Answer 15

1. Hemolytic anemia.
2. Thrombocytopenia.
3. Acute renal failure.

Question 16

What are the exotoxin produced by the Yersinia enterocolitica and what do they do?

Answer 16

Produces a heat-stable toxin: increases cGMP. It causes abdominal pain that resembles an appendicitis.

Question 17

What are the exotoxin produced by the Bacillus anthracis and what do they do?

Answer 17

Anthrax toxin that has three components:

1. Edema factor: It is an Adenylyl cyclase, causing increase of cAMP.
2. Lethal factor.
3. Protective antigen.

Question 18

What are the exotoxin produced by the Vibrio cholerae and what do they do?

Answer 18

Choleragen (cholera toxin): It stimulates adenylyl cyclase, causing increase in cAMP. Causes “rice-water stools” because it causes chlorides and water to cross into the lumen of the intestine. A person affected can lose up to 20L of fluids, causing circulatory collapse.

Question 19

What are the exotoxin produced by the Bordatella pertussis and what do they do?

Answer 19

Pertussis toxin: Binds to and inactivates inhibitory G proteins, causing increase in cAMP.

Question 20

What are the exotoxin produced by the Clostridium tetani and what do they do?

Answer 20

Tetanospasmin: Blocks release of inhibitory neurotransmitters GABA and glycine, causing lock jaw and other muscles spasms.

Question 21

What are the exotoxin produced by the Clostridium botulinum and what do they do?

Answer 21

Exotoxins A-G: Inhibit release of acetylcholine, causing flaccid paralysis (consumption of canned food and babies eating honey).

Question 22

What are the differences between C. tetani and C. botulinum?

Answer 22

C. tetani causes SPASTIC paralysis by blocking GABA and glycine release.

C. botulium causes FLACID paralysis by blocking ACh release at the neuromuscular juntion.

Question 23

What are the exotoxin produced by the Clostridium perfringens and what do they do?

Answer 23

1. Alpha toxin: It is a phospholipase that causes gas gangrene and myonecrosis.
2. Enterotoxin: Food poisoning; food left out for too long.

Question 24

What exotoxin inhibits ACh release, causing flaccid paralysis?

Answer 24

Botulinum toxin.

Question 25

What exotoxin is a phospholipase that causes gas gangrene?

Answer 25

Alpha toxin of Clostridium perfringens.

Question 26

What exotoxin inhibits the inhibitor of adenylate cyclase, causing whooping cough?

Answer 26

Pertussis toxin.

Question 27

What exotoxin stimulates the adenylate cyclase, causing chloride and water into the intestine, causing massive diarrhea?

Answer 27

1. Cholera toxin.

2. Heat liable ETEC toxin.

Question 28

What exotoxin destroys leukocytes?

Answer 28

Staph aureus gama (Y) hemolysin and Panton-Valentine leukocidin.

Question 29

What exotoxin is composed of an edema factor, lethal factor, and protective antigen?

Answer 29

Anthrax toxin.

Question 30

What exotoxin causing rice-water diarrhea?

Answer 30

Cholera toxin.

Heat labile ETEC toxin.

Question 31

What exotoxin causes scarlet fever?

Answer 31

Pyrogenic toxins of Strep pyogenes.

Question 32

What exotoxin causes toxic shock syndrome?

Answer 32

TSST-1 produced by Staph aureus.

Question 33

What exotoxin inactivates EF-2 causing pseudomembranous pharyngitis?

Answer 33

Diptheria toxin.

Question 34

What exotoxin blocks the release of the inhibitory neurotetransmitter glycine?

Answer 34

Tetanospasmin (tetanus toxin).

Question 35

List seven bacteria that secrete enterotoxin.

Answer 35

1. Vibrio cholerae.
2. Enterotoxogenic E. coli.
3. Staphylococcus aureus.
4. Shigella.
5. Yersinia.
6. Clostridium difficile.
7. Clostridium perfringes.

Question 36

What are the similarities and difference of Scarlet fever vs acute rheumatic fever?

Answer 36

Both are caused by group A Strep. However, Scarlet fever is caused by the exotoxin erythrogenic/ pyogenic toxin while acute rheumatic fever is antibody mediated, occurring a few weeks after the infection.

Question 37

What is endotoxin?

Answer 37

Found within the outer membrane of G(-) bacteria. The lipid portion of the lipopolisacharide, called lipid A, is responsible for the toxic effects of endotoxin. The lipid A is trapped within the bacterial structure, but once the bacteria is lysed, the lipid A is released into the host and causes systemic symptoms.