Bacterial exotoxins Flashcards Preview

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Flashcards in Bacterial exotoxins Deck (20):

What bacteria and toxins inhibit protein synthesis

corynebacterium diptheriae (diphtheria toxin), pseudomonas aeruginosa (exotoxin A), shgella (shiga toxin), eneterohemorrhagic E coli, inclusing O157:H7 strain (shiga-like toxin)


diptheria/exotoxin A MOA and manifestation

diptheria from C. diptheria; exotoxin A from pseudomonas aeruginosa.
inactivates elongation factor 2.
exotoxin A causes host cell death; diphtheria causes pharyngitis with pseudomembranes in throat and severe LAD (bull's neck)


How does Shiga toxin work?

seen in shigella and EHEC. inactivates the 60S ribosome by removing adenine from rRNA. in shigella, this causes GI mucosal damage, dysentery (bloody diarrhea),. It also enhances cytokine release and can cause hemolytic uremic syndrome.
EHEC can also cause HUS but won't invade host cells.



hemolytic anemia, acute renal failure, and thrombocytopenia


What bugs/toxins increase fluid secretion?

heat labile and heat stable toxins from entrotoxigenic E coli (ETEC), edema factor from bacillus anthracis, and cholera toxin from vibrio cholera


heat labile toxin

from ETEC. overactivates adenylate cyclase, incr. cAMP, incrl Cl- secretion in gut and H2) efflux. causes watery diarrhea. may be from the air


heat stable toxin

like heat labile toxin, this is also from ETEC. it overactivates the guanylate cyclase, incr. cGMP, and decr. resorption of NaCl. this also causes a watery diarrhea


edema factor

from bacillis anthracis. mimics the adenylate cyclase enzyme to incr. cAMP. this may be responsible for the edematous borders of black eschar in cutaneous anthrax


cholera toxin

from vibrio cholerae. overactivates adenylate cyclase bu permanently activating Gs. this incr. Cl secretion tin the gut and causes H2O efflux


What toxins inhibit phagocytic ability?

pertussis toxin from bordetella pertussis. this overactivates adenylate cyclase and incr. cAMP by diabling Gi. this impairs phagocytosis to incr. survival of the microbe


What toxins inhibt release of neurotransmitter?

tetanospasmin from clostridium tetani and botulinum toxin from clostridium botulinum


How doe tetanospasm toxin and botulinum toxin work?

they are both proteases that cleave SNARE proteins needed for neurotransmitter release


clinical symptoms of tetanus toxin: why?

spasticity, risis sardonicus, lockjaw. this is because the toxin cleaves SNARE proteins needed for release of inhibitory neurtotransmitters (GABA and glycine) from Renshaw cells in the spinal cord


clinical symptoms of botulinum toxin? Why?

faccid paralysis, floppy babies. toxin prevents release of stimulatory ACh signal at the NMJ


What toxins lyse cell membranes?

alpha toxin from clostridium perfringens, and streptolysin O from strep pyrogenes


Alpha toxin

from clostridium perferinges. it is a phspholipase that degrades tissue and cell membranes. degradation of phospholipids causes a myonecrosis and hemolysis (double zone of hemolysis on blood agar)


streptolysin O

protein that degrades cell membranes from srep pyrogenes. lyses RBCs and contributes to beta hemolysis. host antibodies against the toxin (ASO) are used to diagnose rheumatic fever (remeber not to confuse with the immune complexes of post-strep glomerulonephritis)


What toxins cause shock?

TSS toxin from S. aureus, exotoxin A from Strep pyrogenes


How do toxic shock syndrome toxins and exotoxin A work?

superantigens. bring MHC II and T cell receptors together to cause overwheming release of IFN-gamma and IL2. this cause fever, rash, and shock.


Other than TSS, what toxins/sydromes can be produced by staph aureus?

scalded skin syndrome from exfoliative toxin and food poisoning from enterotoxin