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32 Cards in this Set

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Bacterial endotoxins and exotoxins: Source?
Exotoxin: Certain species of gram positive and gram negative bacteria, Endotoxin: Cell wall of most gram-negative bacteria
Bacterial endotoxins and exotoxins: Secreted from cell?
Exotoxin: Yes , Endotoxin: No
Bacterial endotoxins and exotoxins: Chemistry
Exotoxin: Polypeptide, Endotoxin: Lipopolysaccharide
Bacterial endotoxins and exotoxins: Location of genes
Exotoxin: Plasmid or bacteriophage, Endotoxin: Bacterial chromosome
Bacterial endotoxins and exotoxins: Toxicity (fatal dosage)
Exotoxin: High (fatal dose on the order of 1 microgram), Endotoxin: Low (fatal dose on the order of hundreds of micrograms)
Bacterial endotoxins and exotoxins: Clinical effects
Exotoxin: Toxin specific, Endotoxin: Fever and shock
Bacterial endotoxins and exotoxins: Mode of action
Exotoxin: Toxin specific, Endotoxin: Includes TNF and IL-1
Bacterial endotoxins and exotoxins: Antigenicity
Exotoxin: Induces high-titer antibodies called antitoxins, Endotoxin: Poorly antigenic
Bacterial endotoxins and exotoxins: Vaccines
Exotoxin: Toxoids used as vaccines, Endotoxin: No toxoids formed and no vaccine available
Bacterial endotoxins and exotoxins: Heat stability
Exotoxin: Destroyed rapidly at 60 degrees celsius (except Staphylococcal enterotoxin), Endotoxin: Stable at 100 degrees celsius for 1 hour
Bacterial endotoxins and exotoxins: Typical bugs
Exotoxin: Tetanus, botulism, diphtheria, Endotoxin: Meningococcemia, sepsis by gram negative rods
Mechanism of superantigens
1. Bind directly to MHC II and T cell receptor, 2. Large numbers of T cells are activated, 3. Stimulates release of IFN-gamma and IL-2
Mechanism of ADP ribosylating A-B toxins
Interfere with host cell function: B (binding) component binds to a receptor on surface of host cell, The toxin is endocytosed, A (active) component attaches an ADP-ribosyl to a host cell protein, That protein's function is altered.
List of bugs that release superantigens
Staphylococcus aureus, Streptococcus pyogenes
List of bugs that release ADP ribosylating A-B toxins
Corynebacterium diphtheriae, Vibrio cholerae, E. coli, Bordetella pertussis
What to know about exotoxins released by Staphylococcus aureus
Superantigens: TSST-1 causes toxic shock syndrome (fever, rash, shock). Enterotoxins cause food poisoning.
What to know about exotoxins released by Streptococcus pyogenes
Scarlet fever (superantigen): Erythrogenic, Causes toxic shock-like syndrome, Streptolysin O (hemolysin). The antigen for ASO antibody is found in rheumatic fever
What to know about exotoxins released by Corynebacterium diphtheriae
ADP ribosylating A-B toxin (similar to Pseudomonas exotoxin A), Encoded by beta-prophage, Disease: Pseudomembranous pharyngitis (grayish-white membrane) with lymphadenopathy, Mechanism: Inactivates elongation factor 2 (EF-2) Mnemonic: ABCDEFG
What to know about exotoxins released by Vibrio cholerae
A-B toxin ADP ribosylates Gs protein thus, Permanently activates Gs protein, Constant stimulation of adenylyl cyclase which, Increases pumping of Cl into gut, H2O follows it, Leads to rice water diarrhea
What to know about exotoxins released by E. coli
E.coli 0157:H7 produces Shiga toxin. ADP ribosylating A-B toxins, Heat-labile: Permanent activation of adenylyl cyclase (cholera-like mechanism) leading to watery diarrhea, Heat-stabile: Stimulates guanylate cyclase, Mnemonic: Labile like the Air
What to know about exotoxins released by Bordetella pertussis
1. ADP ribosylating A-B toxin, 2. Permanently disables Gi, 3. Constant stimulation of adenylate cyclase, 4. Causes whooping cough, 5. Also inhibits chemokine receptor causing lymphocytosis
What to know about exotoxins released by Clostridium perfringens
alpha toxin (aka lecithinase) causes: 1. gas gangrene, 2. myonecrosis, 3. hemolysis (See double zone of hemolysis on blood agar.), PERFringens PERForates a gangrenous leg.
What to know about exotoxin released by Clostridium botulinum
Properties: 1. Preformed, 2. Heat-labile Mechanism: Blocks the release of acetylcholine causing: 1. anticholinergic symptoms 2. CNS paralysis (especially cranial nerves), 3. Floppy baby syndrome - BOTulinum is from bad BOTtles of food and honey
What to know about exotoxins released by Clostridium tetani
Blocks the release of inhibitory neurotransmitter glycine from Renshaw cells in the spinal cord. Causes "lockjaw"
What to know about exotoxins released by Bacillus anthracis
1 toxin in the toxin complex is edema factor, an adenylate cyclase
What to know about exotoxins released by Shigella
Shiga toxin (also produced by E.coli 0157:H7). Cleaves host cell rRNA. Also enhances cytokine release causing hemolytic uremic syndrome.
Endotoxin: What is it and where is it found?
Lipopolysaccharide found in the outer membrane of gram-negative bacteria. Heat stable.
Endotoxin: What does it activate and what do they release?
1. Macrophages (IL-1, TNF, Nitric oxide), 2. Alternative complement pathway (C3a, C5a), 3. Hageman factor (Coagulation cascade)
What mediators are released when endotoxin activates macrophages, and what do they do?
1. IL-1: Fever, 2. TNF: Fever and Hemorrhagic tissue necrosis, 3. Nitric Oxide: Hypotension (shock)
What mediators are released when endotoxin activates the alternative complement cascade, and what do they do?
1. C3a: Hypotension and edema, 2. C5a: Neutrophil chemotaxis
What mediators are released when endotoxin activates Hageman factor, and what do they do?
Coagulation cascade: Disseminated intravascular coagulopathy
What to know about exotoxins released by S. pyogenes
Streptolysin O is a hemolysin, antigen for ASO antibody in rheumatic fever