Exotoxins

Question 1

Corynebacterium diptheriae

gram + rod

Answer 1

-Diptheria Toxin (ADP ribosylating AB-toxin.
-B/binding-endocytosis. binds to EGF receptors on cardiac and neural cells
A/active-attaches ADP-ribosyl to EF-2
-MOA: inactive elongation factor (EF-2)
–> Pharyngitis w pseudomembranes in throat, severe lymphadenopathy (bull neck) –> (severe, death) Cardiomyopathy*
-the bacteria look like cells w polar granules/dark staining w aniline.

-Vaccine immunity: IgG against the B-binding unit of the Diptheria Exotoxin

Question 2

Pseudomonas aeruginosa

Gram - rod

Answer 2

• Exotoxin A (ADP ribosylating AB-toxin. B/binding-endocytosis, A/active-attaches ADP-ribosyl)
• MOA: inactivate elongation factor (EF-2)
• -> Host cell death

Question 3

Shigella spp
Gram - rod, Lactose - , Oxidase -
SOL (shit outta luck, literally shit - and no oxidase or lactose fermenting abilities)

Answer 3

• Shiga Toxin (ST)
• Inactivate 60S ribosome by removing adenine from rRNA
• -> GI mucosal damage –> dysentery
• ST also enhances cytokine release –> HUS
• Shigella invades host cells
• as little as 10 cells of any shigella spp can cause infection***

Question 4

Enterhohemorrhagic E. coli (EHEC - O157:H7)

Gram - rod

Answer 4

-Shiga-like Toxin (SLT)
MOA: inactivate 60S ribosome by removing adenine from rRNA
–> SLT enhances cytokine release –> HUS (TAU - thrombocytopenia, microangiopathic Anemia, Uremia/renal damage)
-EHEC does not invade host cells (but does cause bloody diarrhea)

Question 5

Enterotoxigenic E. coli ETEC
Heat LABILE
Gram - rod

Answer 5

Heat-Labile toxin (LT)

• MOA: overactivates adenylyl cyclase ( incr cAMP) –> Cl- secretion
• -> Watery diarrhea.

Labile in the Air (adenylyl) and it rains in the air, and rain is like secreting Cl-
Stable on the Ground (Guanylate cyclase)

Question 6

Enterotoxigenic E. coli (ETEC)
Heat STABLE
Gram - rod

Answer 6

Heat stable toxin (ST)

• MOA: overactivates gunylate cyclase (incr cGMP) –> decr resorption of NaCl
• -> water diarrhea

Labile in the Air (adenylyl cyclate) - and it rains in the air, like secreting Cl-
Stable on the Ground (Guanylyate cyclase)

Question 7

Bacillus anthracis

Gram + rod

Answer 7

Edema Factor

• MOA: mimics adenylate cyclase (inc cAMP)
• -> Edematous borders of black eschar in cutaneous anthrax)

Question 8

Vibirio cholerae

Answer 8

Cholera toxin

• MOA: Overactivates adenylate cyclase –> –> incr Cl- secretion
• -> voluminous “Rice-water” diarrhea

Question 9

Bordetella pertussis

Answer 9

Pertussis toxin
-MOA: Overactivates adenlylate cyclase by disabling Gi, also impairs neutrophil chemotaxis/phagocytosis/ox-metabolism to permit survival of microbe
–> Whooping cough (whoops on inspiration, cough on expiration)
“100 day cough” in adults

Question 10

Clostridium tetani

Gram - rod, ANaerobe

Answer 10

Tetanospasmin

• MOA: Cleaves SNARE protein required for NT release
• ->Rigid paralysis, “lock jaw”. Toxin prevents release of inhibitor NT in spinal cord (GABA and GLYCINE)
• see rods w endospore on one end: TENNIS raquets

SNARE the win in the TENNIS Match (active - rigid paralysis)

Question 11

Clostridium botulinum

Gram - rod, ANaerobe

Answer 11

Botulinum toxin

• MOA: Cleaves SNARE protein required for NT release
• -> Flaccid paralysis, floppy baby. Toxin prevents release of stimulatory (Ach) signal at NM jxns
• -> The THREE D’s: Diplopia (double vision), Dysphagia, Dysphonia (hoarse voice)

Question 12

Clostridium perfringens

Gram - rod, ANaerobe

Answer 12

Alpha toxin or Phospholipase C

• MOA: Phospholipase that degrades tissue and cell membranes
• -> myonecrosis (“gas gangrene”) and hemolysis (“Double zone” of hemolysis on blood agar)

Alpha Cadet in war causes double zone of hemolysis and gas gangrene by inhibiting major phosphlipase

Question 13

Streptococus pyogenes
Exotoxin: Streptolysin O
Group A strep, gram + cocci

Answer 13

• MOA: degrades cell membrane
• -> lyse rbcs, contributes to Beta-hemolysis
• Host antibodies against toxin (ASO) use to diagnose rheumatic fever

Question 14

Staph aureus
(TSST-1)
Gram + cocci, Catalase/Coagulase+

Answer 14

Toxic Shock Syndrome Toxin (TSST-1)

• MOA: SUPERANTIGEN. Bring MHC2 and TCR in proximity outside of antigen binding site –> overwhelming release of IFN-gamma (from macrophages) and IL-2 (from t cells)
• -> Fever, rash, SHOCK. Desquamation of skin 1-2 days after onset.
• Assoc w tampons and nasal packing

Question 15

Staph aureus
Exfoliative toxin
Gram + cocci, Catalase/Coagulase+

Answer 15

Scalded Skin Syndrome

SUPERANTIGEN

Question 16

Staph aureus
Enterotoxin
Gram + cocci, Catalase/Coagulase+

Answer 16

Food poisoning

Question 17

Strep pyogenes
Exotoxin A
Group A strep, gram + cocci

Answer 17

• MOA: Bring MHC2 and TCR in proximity outside of antigen binding site –> mass release of IFN-gamma and IL-2
• -> Fever, Rash, SHOCK

SUPERANTIGEN

Question 18

cAMP (mnemonic: those that incr cAMP levels)

Answer 18

c = Cholera (Vibiro cholerae)
A = Anthrax (Bacillus anthracis)
M = Montezuma's revenge (popular name for ETEC - LT)
P = Pertussis (Bordetella pertussis)