Bacterial exotoxins

Question 1

What bacteria and toxins inhibit protein synthesis

Answer 1

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

Question 2

diptheria/exotoxin A MOA and manifestation

Answer 2

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)

Question 3

How does Shiga toxin work?

Answer 3

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.

Question 4

HUS

Answer 4

hemolytic anemia, acute renal failure, and thrombocytopenia

Question 5

What bugs/toxins increase fluid secretion?

Answer 5

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

Question 6

heat labile toxin

Answer 6

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

Question 7

heat stable toxin

Answer 7

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

Question 8

edema factor

Answer 8

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

Question 9

cholera toxin

Answer 9

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

Question 10

What toxins inhibit phagocytic ability?

Answer 10

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

Question 11

What toxins inhibt release of neurotransmitter?

Answer 11

tetanospasmin from clostridium tetani and botulinum toxin from clostridium botulinum

Question 12

How doe tetanospasm toxin and botulinum toxin work?

Answer 12

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

Question 13

clinical symptoms of tetanus toxin: why?

Answer 13

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

Question 14

clinical symptoms of botulinum toxin? Why?

Answer 14

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

Question 15

What toxins lyse cell membranes?

Answer 15

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

Question 16

Alpha toxin

Answer 16

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)

Question 17

streptolysin O

Answer 17

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)

Question 18

What toxins cause shock?

Answer 18

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

Question 19

How do toxic shock syndrome toxins and exotoxin A work?

Answer 19

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

Question 20

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

Answer 20

scalded skin syndrome from exfoliative toxin and food poisoning from enterotoxin