Micro - Basic Bacteriology (Exotoxins & Endotoxins) Flashcards Preview

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Flashcards in Micro - Basic Bacteriology (Exotoxins & Endotoxins) Deck (40):
1

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

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

2

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

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

3

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

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

4

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

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

5

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

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

6

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

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

7

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

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

8

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

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

9

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

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

10

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

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

11

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

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

12

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

(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)

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).

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

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).

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

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)?

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)

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)?

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

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)?

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

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)?

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

19

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

(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

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.

(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)"

21

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

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

22

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

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

23

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

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)

24

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

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

25

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

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

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)?

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

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)?

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

28

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

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

29

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

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)

30

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

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)

31

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

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

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)?

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

33

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

Exfoliative toxin - Scalded skin syndrome; Enterotoxin - Food poisoning

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)?

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

35

What is endotoxin?

A lipopolysaccharide found in outer membrane of gram-negative bacteria

36

What main things should you associate with endotoxin?

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

37

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

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

38

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

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

39

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

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

40

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

Coagulation cascade --> DIC

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