Micro 2 - Bacterial Toxins Flashcards
What does endotoxin affect in the body?
Macrophages, complement system and tissue factor liberation.
What are exotoxins?
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).
What do neurotoxins do and what are two examples of them?
They interfere with neural transmission.
- Botulinum toxin.
- Tetanus toxin.
What do enterotoxins do and what are some examples of them?
They affect the intestines.
- Shigella.
- Vibrio cholera.
What are superantigens?
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.
What are the two best know bacteria to release Superantigens?
- Staphylococcus aureus.
2. Streptococcus pyogenes.
What known toxins are secreted by Staph aureus and what are the actions of each?
- Alpha-toxin: hemolysis.
- Beta-toxin: sphingomyelinase.
- Proteins A, B, and C, of gama-toxin (Y): A+B= hemolysin, B+C= leukocidin.
- Delta hemolysin: hemolysis.
- Panton-Valentine leukocidin: destroys leukocytes.
What are the three superantigens produced by Staph auereus?
- Enterotoxins A-E: from food poisoning, causing vomiting and diarrhea.
- TSST-1: causes release of cytokines, causing toxic shock syndrome.
- Epidermolytic/exfoliative toxin: causes epithelial cell lysis, causing scalded skin syndrome.
What are the symptoms of Toxic shock syndrome?
High fever, hypotension and a diffuse rash that looks like a sunburn.
What known toxins are secreted by Streptococcus pyogenes (group A strep)? What is the action of each?
- 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).
- Streptolysin S: hemolysis (Oxygen Stable).
- Erythrogenic/ pyrogenic toxins: Skin rash (erythro-) and fever (pyro-) of scarlet fever. They act as superantigens.
What does the diptheria toxin produced by the Corynebacterium diphtheriae do?
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.
What are the exotoxin produced by the Pseudomonas aeruginosa and what do they do?
Exotoxin A: targets EF-2.
What are the exotoxin produced by the Shigella and what do they do?
Shiga toxin: It cleaves host rRNA at adenine base in 60s ribosomal subunit. It causes inhibition of protein synthesis, leading to cell death.
What are the exotoxin produced by the toxin-producing E. coli and what do they do?
- 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. - 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).
What are the symptoms of Hemolytic-uremic syndrome (HUS)?
- Hemolytic anemia.
- Thrombocytopenia.
- Acute renal failure.
What are the exotoxin produced by the Yersinia enterocolitica and what do they do?
Produces a heat-stable toxin: increases cGMP. It causes abdominal pain that resembles an appendicitis.
What are the exotoxin produced by the Bacillus anthracis and what do they do?
Anthrax toxin that has three components:
- Edema factor: It is an Adenylyl cyclase, causing increase of cAMP.
- Lethal factor.
- Protective antigen.
What are the exotoxin produced by the Vibrio cholerae and what do they do?
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.
What are the exotoxin produced by the Bordatella pertussis and what do they do?
Pertussis toxin: Binds to and inactivates inhibitory G proteins, causing increase in cAMP.
What are the exotoxin produced by the Clostridium tetani and what do they do?
Tetanospasmin: Blocks release of inhibitory neurotransmitters GABA and glycine, causing lock jaw and other muscles spasms.
What are the exotoxin produced by the Clostridium botulinum and what do they do?
Exotoxins A-G: Inhibit release of acetylcholine, causing flaccid paralysis (consumption of canned food and babies eating honey).
What are the differences between C. tetani and C. botulinum?
C. tetani causes SPASTIC paralysis by blocking GABA and glycine release.
C. botulium causes FLACID paralysis by blocking ACh release at the neuromuscular juntion.
What are the exotoxin produced by the Clostridium perfringens and what do they do?
- Alpha toxin: It is a phospholipase that causes gas gangrene and myonecrosis.
- Enterotoxin: Food poisoning; food left out for too long.
What exotoxin inhibits ACh release, causing flaccid paralysis?
Botulinum toxin.
What exotoxin is a phospholipase that causes gas gangrene?
Alpha toxin of Clostridium perfringens.
What exotoxin inhibits the inhibitor of adenylate cyclase, causing whooping cough?
Pertussis toxin.
What exotoxin stimulates the adenylate cyclase, causing chloride and water into the intestine, causing massive diarrhea?
- Cholera toxin.
2. Heat liable ETEC toxin.
What exotoxin destroys leukocytes?
Staph aureus gama (Y) hemolysin and Panton-Valentine leukocidin.
What exotoxin is composed of an edema factor, lethal factor, and protective antigen?
Anthrax toxin.
What exotoxin causing rice-water diarrhea?
Cholera toxin.
Heat labile ETEC toxin.
What exotoxin causes scarlet fever?
Pyrogenic toxins of Strep pyogenes.
What exotoxin causes toxic shock syndrome?
TSST-1 produced by Staph aureus.
What exotoxin inactivates EF-2 causing pseudomembranous pharyngitis?
Diptheria toxin.
What exotoxin blocks the release of the inhibitory neurotetransmitter glycine?
Tetanospasmin (tetanus toxin).
List seven bacteria that secrete enterotoxin.
- Vibrio cholerae.
- Enterotoxogenic E. coli.
- Staphylococcus aureus.
- Shigella.
- Yersinia.
- Clostridium difficile.
- Clostridium perfringes.
What are the similarities and difference of Scarlet fever vs acute rheumatic fever?
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.
What is endotoxin?
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.
