Bacterial Toxins

ekadar's version from 2016-05-12 16:40


Question Answer
Where are endotoxins found?Outer membrane of gram negatives (LPS)
3 main targets of endotoxins(1) Macrophages (2) Complement (3) Tissue factor
What inflammatory mediators are activated by Macrophages?IL-1, IL-6
IL-1Fever/ osteoclast activating factor
TNF-alphaCell death > Fever, hypotension, Cachexia
How does Complement induce endoctoxin damage?C3a and C3b
C3aHypotension and Edema
C5aNeutrophil Chemotaxis
Tissue factorActivates Coagulation Cascade >> DIC


Question Answer
Inactivates EF-2C. Diptheriae, Pseudomonas
Gray pseudomembranes and bull neckC. Diptheriae (EF-2)
Which organ systems are particularly vulnerable to EF-2?Heart, and nerve cells
Exotoxin APseudomonas
Causes host cell deathPseudomonas: Exotoxin A
Mechanism of shiga toxin?Inactivates 60S ribosome by removing adenine from rRNA
Removes adenine from rRNA on 60S ribosomeShigella (ST) and EHEC 0157:H7 (SLT)
Inhibit protein synthesisInactivate EF-2: Diptheria and Pseudomonas
Inactivate 60S ribosomal subunit: Shigella (ST) and EHEC 0157:H7 (SLT)
Hemolytic anemia
Acute renal failure
HUS: Shigella and EHEC 0157:H7
Dysentary from GI mucosal damageShigella (ST)
What is the difference between Shigella (ST) and EHEC (SLT)?EHEC does not invade host cells
Stimulates cAMP in gut >> Cl- secretion in gutETEC and Cholera
Overactivates cGMP in gut >> Decrease resorption of NaClHeat Stable ETEC (ST)
Mimics adenylyl cyclase enzyme to increase cAMPBacillus anthracis
What are the components of anthrax toxin?Edema toxin, Lethal factor, Protective antigen
Black escharEdema toxin mimics AC >> stimulates cAMP
Watery diarrheaETEC (LT, ST), Vibrio cholera
"pseudoappendicitis"Yersinia enterolytica stimulates cGMP
Exotoxin of whooping cough?Pertussis toxin: Disables Gi to overactivates cAMP
Cleave SNARE proteinsClostridium tetani and botulinum.
What does SNARE usually do?Allows NT release. Inhibits NT when cleaved.
Exotoxin causing spastic paralysis?Tetanospasmin: Cleaves SNARE to prevent release of GABA and glycine
Exotoxin causing descending flaccid paralysis?Botulinum: Cleaves SNARE to inhibit ACh release at the NMJ
Exotoxin causing gas gangrene and double zone hemolysis?C.perfringens: Alpha toxin
Alpha toxin?Phospholipase degrades tissue and cell membranes [C. Perfringens]
How do superantigens cause shock?Bind MHCII and T cells simultaneously (crosslink) >> Polyclonal T cell expansion >> Uncontrolled cytokine release
Binds to MHCII and TCR to cause release of IL-1, IL-2, IFN-gamma and TNF alphaStaph aureus: TSST-1, S. pyogenes: Exotoxin A
Scalded skin syndromeS. Aureus Exfoliative toxin
Oxygen Stable toxinGAS: Streptolysin S
Oxygen LabileGAS: streptolysin O
Destroys leukocytesS. aureus: Leukocidin toxin
Diarrhea 2-6 hours after eating mayo (eggs, dairy, potato salad)S. aureus enterotoxin (pre-formed, heat stable)
Traveler's diarrheaETEC
LT toxin of ETEC similar toCholera
Mechanism of LT ETEC toxinactivates adenylate cyclase leading to increased intracellular CAMP like Cholera!
Mechanism of tetrodotoxin (pufferfish poisoning)binds to voltage-gated sodium channels in nerve and cardiac tissues preventing sodium influx and depolarization

Toxins that Inhibit Protein Synthesis

Question Answer
Diptheria toxininactivates EF2 via intracellular protein ribosylation
Pseudomonas Toxin Ainactivates EF2
Shiga toxininactivates 60s ribosome by removing adenine from rRNA

Toxins that Increase Fluid Secretion

Question Answer
ETEC LT toxinoveractivates adenylate cyclase-increasing CAMP-increasing Cl secretion
ETEC SToveractivates guanylate cyclase (increasing cGMP) decreases resorption of NACl and H20 in gut
Bacillus anthracis edema toxinmimics adenylate cyclase enzyme (increases CAMP)
cholera toxinoveractivates adentylate cyclase (increases CAMP) by permanently activating GS

Toxins that Inhibit Phagocyctic ability

Question Answer
Pertussis toxinoveractivates adenylate cyclase (increases CAMP) by disabling G1, impairing phagocytosis
what is the relationship between pertussis and islet of langerhansactivates islets and can cause hypoglycemia

Inhibit Release of Neurotransmitter

Question Answer
Tetanospasmininhibits release of inhibitor neurotransmitters (GABA and glycine)
Botulinumtoxin prevents release of stimulatory (Ach) signals at NMJ junctions
flaccid paralysisbotulinum
spastic paralysistetanospasm

Other Virulence Factors

Question Answer
IgA ProteaseS. pneumo + H. influenza