The Mess That Is Micro - III - Toxins Flashcards
Bugs with exotoxins that inhibit protein synthesis
How to remember: Dip pseudofed in Shampagne and you will bleed. (note: I doubt you actually will)
Diptheria - diptheria toxin
Pseudomonas - exotoxin A
Shigella - shiga toxin
EHEC - shiga-like toxin
Exotoxin A
Pseudomonas aeruginosa (associated with elongation factor 2)
Shiga-like toxin
EHEC
Inactivates 60S ribosome (the host’s ribosome!!) by cleaving adenine in RNA. N-glycosidase function - cleaves adenine nucleobase from 28S ribosome.
SLT-toxin enhances cytokine release causing HUS - unlike shigella, EHEC does not invade host cells.
Shigella spp. What kind of toxin?
Shiga toxin - inactivates the 60s ribosome in eukaryotic cells by removing adenine from rRNA - n-glycosidase function, cleaves adenine nucleobase from 28S. GI mucosal damage - dysentery, ST also enhances cytokine release causing HUS.
However NOTE THAT the shiga toxin is less important than intestinal invasion in disease pathogenesis because even nontoxin producing shigella produces significant disease!
What bacteria release toxins that increase fluid secretion?
Attacking ants vibrate (and secrete fluid to drown their enemies)
ETEC - heat labile and heat stabile toxin
Bacillus anthracis - Edema factor
Vibrio cholera - cholera toxin
ETEC - what kind of toxin?
Heat-labile toxin - overactivates adenylate cyclase (increase cAMP) through gs–> increase Cl secretion in gut and H2O efflux.
Heat-stabile toxin - overactivates guanylate cyclase (increased cGMP) leads to decreased resorption of nacl and h2o in the gut.
Remember: labile in the air (adenylate cyclase), stabile on the ground (guanylate cyclase).
Remember: Camp with chlorine if you don’t want to get traveller’s diarrhea and cholera!
What bacteria release toxins that increase fluid secretion?
Remember: Attacking (ETEC) ants (Bacillus anthracis) vibrate (Vibrio cholera) (and secrete fluid to drown their enemies)
ETEC - heat labile and heat stabile toxin
Bacillus anthracis - Edema factor
Vibrio cholera - cholera toxin
What causes HUS?
Shigella
EHEC
Damage to endothelial cells is the primary event in the pathogenesis of hemolytic-uremic syndrome (HUS). The cardinal lesion is composed of arteriolar and capillary microthrombi (thrombotic microangiopathy [TMA]) and red blood cell (RBC) fragmentation.
Verotoxin
Same as shiga-like toxin, produced by EHEC
Bacillus anthracis - toxin?
Edema factor - mimics the adenylate cyclase enzyme - increases cAMP
Likely responsible for the characteristic black borders of an eschar in cutaneous anthrax.
Remember: anthrax gives you a black eschar with EDEMA.
Bugs that inhibit phagocytic activity?
Bordetella pertussis - pertussis toxin
Vibrio cholerae
Cholera toxin / Choleragen - overactivates adenylate cyclase/ cAMP by permanently activating Gs and thus increases Cl secretion in gut and H2O efflux. Leads to voluminous rice water diarrhea.
Remember: Put Chlorine in your water at CAMP or you might get heat labile ETEC and Cholera!
Bordetella pertussis toxin?
Pertussis toxin - overactivates adenylate cyclase and increases cAMP by disabling Gi, impairing phagocytosis to permit survival of the microbe. Leads to whooping cough.
Pathway for th1, interferon, macrophages, and il-12
This interfering macro is making me Ill
Th1 makes interferon to stimulate macrophages
Mcrophages make il-12 to stimulate th1.
Clostridium tetani toxin?
Tetanospasmin - protease that cleaves SNARES proteins required for neurotransmitter release.
Spasticity, risus sardonus, lockjaw, toxin prevents release of inhibitory GABA and glycine neurotransmitters from Renshaw cells in the spinal cord.
Clostridium botulinum
Botulinum toxin - protease that cleaves SNARES proteins required for neurotransmitter release.
Flaccid paralysis, floppy baby, toxin prevents release of stimulatory Ach signals at neuromuscular junctions leading to flaccid paralysis.
Clostridium perfringens toxin
Alpha toxin- phospholipase - lecithinase- degrades tissue and cell membranes.
Degradation of phospholipids, myonecrosis (gas gangrene) and hemolysis (double sone of hemolysis on blood agar)
Remember: Elves (alpha) on the Fringe (perfringens) are Less (lecithinase) likely to get Gassed (gas gangrene)