Micro - Basic Bacteriology (Exotoxins & Endotoxins)

Question 1

What is the difference between Exotoxin and Endotoxin in terms of source?

Answer 1

EXOTOXIN - Certain species of some gram-positive and gram-negative bacteria; ENDOTOXIN - Outer cell membrane of most gram-negative bacteria

Question 2

What is the difference between Exotoxin and Endotoxin in terms of secretion from cells?

Answer 2

EXOTOXIN - Yes, secreted from cells; ENDOTOXIN - No, not secreted from cells (structural part of bacteria, released upon cell death and lysis)

Question 3

What is the difference between Exotoxin and Endotoxin in terms of chemistry?

Answer 3

EXOTOXIN - Polypeptide; ENDOTOXIN - Lipopolysaccharide (structural part of bacteria; released when lysed)

Question 4

What is the difference between Exotoxin and Endotoxin in terms of location of genes?

Answer 4

EXOTOXIN - (typically) Plasmid or bacteriophage; ENDOTOXIN - Bacterial chromosome

Question 5

What is the difference between Exotoxin and Endotoxin in terms of toxicity?

Answer 5

EXOTOXIN - High (fatal dose on the order of 1 microgram); ENDOTOXIN - Low (fatal dose on the order of hundreds of micrograms)

Question 6

What is the difference between Exotoxin and Endotoxin in terms of clinical effects?

Answer 6

EXOTOXIN - Various effects (see later cards for specific information on bugs with exotoxins); ENDOTOXIN - Fever, shock

Question 7

What is the difference between Exotoxin and Endotoxin in terms of mode of action?

Answer 7

EXOTOXIN - Various modes (see later cards for specific information on bugs with exotoxins); ENDOTOXIN - Induces TNF and IL-1

Question 8

What is the difference between Exotoxin and Endotoxin in terms of antigenicity?

Answer 8

EXOTOXIN - Induces high-titer antibodies called antitoxins; ENDOTOXIN - Poorly antigenic

Question 9

What is the difference between Exotoxin and Endotoxin in terms of vaccines?

Answer 9

EXOTOXIN - Toxoids used as vaccines; ENDOTOXIN - No toxoids formed and no vaccine available

Question 10

What is the difference between Exotoxin and Endotoxin in terms of heat stability?

Answer 10

EXOTOXIN - Destroyed rapidly at 60 C (except staphylococcal enterotoxin); ENDOTOXIN - Stable at 100 C for 1 hour

Question 11

What is the difference between Exotoxin and Endotoxin in terms of typical diseases?

Answer 11

EXOTOXIN - Tetanus, botulism, diphtheria; ENDOTOXIN - Meningococcemia, Sepsis by gram–negative rods

Question 12

What are the 4 bacteria with exotoxins that inhibit protein synthesis? Give names of bacteria and their exotoxin(s).

Answer 12

(1) Corynebacterium diphtheriae - Diphtheria toxin (2) Pseudomonas aeruginosa - Exotoxin A (3) Shigella spp. - Shiga toxin (ST) (4) Enterohemorrhagic E. coli (EHEC), including O157:H7 strain - Shiga-like toxin (SLT)

Question 13

Of the bacteria with exotoxins that inhibit protein synthesis, which have a mechanism that inactivates elongation factor (EF-2)? Give names of bacteria and their exotoxin(s).

Answer 13

(1) Corynebacterium diphtheriae - Diphtheria toxin (2) Pseudomonas aeruginosa - Exotoxin A

Question 14

Of the bacteria with exotoxins that inhibit protein synthesis, which have a mechanism that inactivates 60S ribosome by removing adenine from rRNA? Give names of bacteria and their exotoxin(s).

Answer 14

(1) Shigella spp. - Shiga toxin (ST) (2) Enterohemorrhagic E. Coli (EHEC), including O157:H7 strain - Shiga-like toxin (SLT)

Question 15

What is the exotoxin associated with Corynebacterium diphtheriae? Give the following for this exotoxin: general function, specific mechanism, and clinical manifestation. What other exotoxin shares its mechanism, and what bacteria secretes this exotoxin(s)?

Answer 15

Diphtheria toxin; Inhibit protein synthesis; Inactivate elongation factor (EF-2) (like P. aeruginosa’s Exotoxin A); Pharyngitis with pseudomembranes in throat and severe lymphadenopathy (bull neck)

Question 16

What is the exotoxin associated with Pseudomonas aeruginosa? Give the following for this exotoxin: general function, specific mechanism, and clinical manifestation. What other exotoxin shares its mechanism, and what bacteria secretes this exotoxin(s)?

Answer 16

Exotoxin A; Inhibit protein synthesis; Inactivate elongation factor (EF-2) (like Corynebacterium diphtheriae’s Diphtheria toxin); Host cell death

Question 17

What is the exotoxin associated with Shigella spp.? Give the following for this exotoxin: general function, specific mechanism, and clinical manifestation. What other exotoxin shares its mechanism, and what bacteria secretes this exotoxin(s)?

Answer 17

Shiga toxin (ST); Inhibit protein synthesis; Inactivate 60S ribosome by removing adenine from rRNA (like Shiga-like toxin (SLT) from Enterohemorrhagic E. coli [EHEC], including O157:H7 strain); (1) GI mucosal damage –> dysentery (2) ST also enhances cytokine release, causing HUS

Question 18

What is the exotoxin associated with Enterohemorrhagic E. Coli (EHEC), including the O157:H7 strain? Give the following for this exotoxin: general function, specific mechanism, and clinical manifestation. What other exotoxin shares its mechanism, and what bacteria secretes this exotoxin(s)?

Answer 18

Shiga-like toxin (SLT); Inhibit protein synthesis; Inactivate 60S ribosome by removing adenine from rRNA (like Shiga toxin of Shigella spp.); (1) SLT enhances cytokine release, causing HUS (2) Unlike Shigella, EHEC does NOT invade host cells

Question 19

What are the 3 bacteria with exotoxins that increase fluid secretion? Give names of bacteria and their exotoxin(s).

Answer 19

(1) Enterotoxigenic E. coli (ETEC) - (a) Heat-labile toxin (LT) (b) Heat-stable toxin (ST) (2) Bacillus anthracis - Edema factor (3) Vibrio cholerae - Cholera toxin

Question 20

What is/are the exotoxin(s) associated with Entertoxigenic E.coli (ETEC)? Give the following for this/these exotoxin(s): general function, specific mechanism, and clinical manifestation.

Answer 20

(1) Heat-labile toxin (LT) - Increase fluid secretion, Overactivates adenylate cyclase (increasing cAMP) –> increased Cl- secretion in gut and H2O efflux (2) Heat-stable toxin (ST) - Increase fluid secretion, Overactivates guanylate cyclase (increasing cGMP) –> decreased resorption of NaCL and H2O in gut; Both LT & ST cause Watery diarrhea; Think: “LABILE in the Air (Adenylate cyclase) & STABLE on the Ground (Guanylate cyclase)”

Question 21

What is the exotoxin associated with Bacillus anthracis? Give the following for this exotoxin: general function, specific mechanism, and clinical manifestation.

Answer 21

Edema factor; Increase fluid secretion; Mimics the adenylate cyclase enzyme (increasing cAMP); Likely responsible for characteristic edematous borders of black eschar in cutaneous anthrax

Question 22

What is the exotoxin associated with Vibrio cholerae? Give the following for this exotoxin: general function, specific mechanism, and clinical manifestation.

Answer 22

Cholera toxin; Increase fluid secretion; Overactivates adenylate cyclase (increasing cAMP) by permanently activating Gs –> increased Cl- secretion in gut and H2O efflux; Voluminous “rice-water” diarrhea

Question 23

What is the exotoxin associated with Bordetella pertussis? Give the following for this exotoxin: general function, specific mechanism, and clinical manifestation.

Answer 23

Pertussis toxin; Inhibit phagocytic activity; Overactivates adenylate cyclase (increasing cAMP) by disabling Gi, impairing phagocytosis to permit survival to microbe; Whooping cough: Child coughs on expiration and “whoops” on inspiration (toxin may not actually be cause of cough; can cause “100-day cough” in adults)

Question 24

What are the defining characteristics of ribosylating A-B toxins? Give 5 examples of such exotoxins and the bacteria that secretes each?

Answer 24

B (binding) component binds to host cell surface receptor, enabling endocytosis & A (active) component attaches ADP-ribosyl to disrupt host cell proteins; (1) Diphtheria toxin from Corynebacterium diphtheriae (2) Exotoxin A from Pseudomonas aeruginosa (3) Heat-labile toxin (LT) from Enterotoxigenic E. coli (ETEC) (4) Cholera toxin from Vibrio cholerae (5) Pertussis toxin from Bordetella pertussis

Question 25

What are 2 bacteria with exotoxins that inhibit release of neurotransmitters? Give names of bacteria and their exotoxin(s).

Answer 25

(1) Clostridium tetani - Tetanospasmin (2) Clostridium botulinum - Botulinum toxin

Question 26

What is the exotoxin associated with Clostridium tetani? Give the following for this exotoxin: general function, specific mechanism, and clinical manifestation. What other exotoxin shares its mechanism, and what bacteria secretes this exotoxin(s)?

Answer 26

Tetanospasmin; Inhibit release of neurotransmitter; Cleave SNARE protein required for neurotransmitter release (like Clostridium botulinum’s Botulinum toxin); Spasticity, risus sardonicus, and “lock jaw”: toxin prevents release of inhibitory (GABA and glycine) neurotransmitters from Renshaw cells in spinal cord

Question 27

What is the exotoxin associated with Clostridium botulinum? Give the following for this exotoxin: general function, specific mechanism, and clinical manifestation. What other exotoxin shares its mechanism, and what bacteria secretes this exotoxin(s)?

Answer 27

Botulinum toxin; Inhibit release of neurotransmitter; Cleave SNARE protein required for neurotransmitter release (like Clostridium tetani’s Tetanospasmin); Flaccid paralysis, floppy baby: Toxin prevents release of stimulatory (ACh) signals at neuromuscular junctions –> flaccid paralysis

Question 28

What are 2 bacteria with exotoxins that lyse cell membranes? Give names of bacteria and their exotoxin(s).

Answer 28

(1) Clostridium perfringens - Alpha toxin (2) Streptococcus pyogenes - Streptolysin O

Question 29

What is the exotoxin associated with Clostridium perfringens? Give the following for this exotoxin: general function, specific mechanism, and clinical manifestation.

Answer 29

Alpha toxin; Lyse cell membranes; Phospholipase that degrades tissue and cell membranes; Degradation of phospholipid C –> (1) Myonecrosis (“gas gangrene”) (2) Hemolysis (“double zone” of hemolysis on blood agar)

Question 30

What is the cell-lysing exotoxin associated with Streptococcus pyogenes? Give the following for this exotoxin: general function, specific mechanism, and clinical manifestation.

Answer 30

Streptolysin O; Lyse cell membranes; Protein that degrades cell membrane; Lyses RBCs, contributing to Beta-hemolysis, Host antibodies against toxin (ASO) used to diagnose rheumatic fever (do not confuse with immune complexes of post-streptococcal glomerulonephritis)

Question 31

What are 2 bacteria with exotoxins that are superantigens capable of causing shock? Give names of bacteria and their exotoxin(s).

Answer 31

(1) Staphylococcus aureus - Toxic shock syndrome toxin (TSST-1) (2) Streptococcus pyogenes - Exotoxin A

Question 32

What is the superantigen exotoxin associated with Staphylococcus aureus? Give the following for this exotoxin: general function, specific mechanism, and clinical manifestation. What other exotoxin shares its mechanism, and what bacteria secretes this exotoxin(s)?

Answer 32

Toxic shock syndrome toxin (TSST-1); Superantigens causing shock; Bring MHC II and TCR in proximity to outside of antigen binding site to cause overwhelming release of IFN-gamma and IL-2 –> shock (like Streptococcus pyogenes’ Exotoxin A); Toxic shock syndrome: Fever, rash, shock

Question 33

Besides TSST-1, what are other exotoxins associated with S. aureus and their associated clinical conditions?

Answer 33

Exfoliative toxin - Scalded skin syndrome; Enterotoxin - Food poisoning

Question 34

What is the superantigen exotoxin associated with Streptococcus pyogenes? Give the following for this exotoxin: general function, specific mechanism, and clinical manifestation. What other exotoxin shares its mechanism, and what bacteria secretes this exotoxin(s)?

Answer 34

Exotoxin A; Superantigens causing shock; Bring MHC II and TCR in proximity to outside of antigen binding site to cause overwhelming release of IFN-gamma and IL-2 –> shock (like Staphylococcus aureus’ TSST-1); Toxic shock syndrome: Fever, rash, shock

Question 35

What is endotoxin?

Answer 35

A lipopolysaccharide found in outer membrane of gram-negative bacteria

Question 36

What main things should you associate with endotoxin?

Answer 36

ENDOTOXIN: Edema, Nitric oxide, DIC/Death, Outer membrane, TNF-alpha, O-antigen, eXtremely heat stable; IL-1; Neutrophil chemotaxis

Question 37

What is the especially antigenic component of Endotoxin? What 3 things does it/Endotoxin activate?

Answer 37

Lipid A; Activates: (1) Macrophages (2) Complement (3) Tissue Factor

Question 38

What results from the activation of macrophages by Endotoxin (Lipid A)?

Answer 38

(1) IL-1 –> Fever (2) TNF –> Fever & hypotension (3) Nitric oxide –> Hypotension

Question 39

What results from the activation of complement by Endotoxin (Lipid A)?

Answer 39

(1) C3a –> hypotension, edema (2) C5a –> Neutrophil chemotaxis

Question 40

What results from the activation of tissue factor by Endotoxin (Lipid A)?

Answer 40

Coagulation cascade –> DIC