Bacterial Toxins & Enzymes Flashcards
These exotoxins non-specifically activate T cells and cause overwhelming cytokine secretion.
Superantigens -
S. pyogenes exotoxin A
S. aureus TSST-1 & Enterotoxin Type B
What is the function of exfoliating toxins (ETA & ETB)?
Serine proteases that cleave a desmosomal protein in keratinocytes that hold cells together.
Hyanuronidase
Cleaves hyaluronic acid in the epithelial cell matrix to facilitate tissue penetration.
This toxin is phospholipase and targets cholesterol in the cell membrane. The toxin is directly responsible for gas gangrene and myonecrosis.
Clostridium perfringens alpha toxin
These toxins are produced by S. pyogenes infected with a lysogenic phage and act as superantigens that cause toxic shock, necrotizing fasciitis, and scarlet fever.
Pyrogenic exotoxins (Spe toxins)
This toxin disrupts the membrane by creating pores and causing hemolysis.
S. aureus alpha toxin
True or False. Hemolysins lyse lymphocytes.
False. Hemolysins lyse red blood cells.
This bacterial enzyme degrades neuraminic acid (sialic acid) in the intracellular cement of the epithelial cells of the intestinal mucosa.
Neuraminidase
What toxins act on EF2 to inhibit protein elongation and ultimately cell death?
Diphtheria toxin & Exotoxin A
What is the function of Listeriolysin O?
Acid activated, pore-forming cytolysin
This toxin cleaves SNARE proteins that prevents release of GABA and causes spastic paralysis.
Clostridium tetani tetanospasmin
Phospholipase
Breaks down phospholipids in the cell membrane
(ex: Clostridium alpha toxin)
This bacterial enzyme converts plasminogen to plasmin, which digests fibrin and prevents blood clotting.
Streptokinase / Staphylokinase
What toxin cleaves SNARE proteins, preventing release of Ach at the musculoskeletal junction, resulting in flaccid paralysis?
Clostridium botulinum toxin
Lecithinase
Destroys lecithin in the cell membrane.
This toxin is produced by S. pneumoniae to degrade hemoglobin, bind cholesterol in the membrane and create pores, and lyse ciliated epithelial cells and phagocytes.
Pneumolysin
This bacterial enzyme lyses phagocytes and their granules.
Leukocidin (Panton-Valentine Factor) / Streptolysin
What gives G- bacteria their endotoxin ability?
Lipid A in the LPS outer membrane
What enzyeme coverts H2O2 to H2O and O2 and is used to differentiate between staphylococcus from streptococci?
Catalase
Collagenase
Breaks down collage in connective tissues to facilitate bacterial invasion.
These toxins target ribosomes to inhibit protein synthesis. They also enhance cytokine release that damages the glomerular endothelial cells and may lead to kidney failure.
Shiga Toxin & Shiga-like Toxin
This protein is located in the cell wall of staphylococci and binds the Fc portion of IgG and inhibits opsonization of the bacteria.
Staphylococcal Protein A
This enzyeme coverts fibrin to fibrinogen to form clots.
Coagulase
This enzyme enables resistance to penicillin antibiotics.
Beta lactamase
What is the mechanism of action of the Cholera toxin?
The toxin riboyslizes the G protein, keeping the alpha subunit in the active state. This overactivates the adenylate cyclase leading to an increased concentration of cAMP. Increased cAMP results in excretion of Cl- and H2O from the gut and leads to life-threatening diarrhea.
(Enterotoxigenic E. coli, Yersinia enterocolitica, and Bacillus anthracis have similar toxins and mechanisms.)
What toxins are produced by B. anthracis and what are their functions?
Protective antigen (PA) - binds to host cell
Edema factor (EF) - adenylate cyclase that increases cAMP and causes tissue edema
Lethal factor (LF) - stimulates macrophages to release cytokines, lyses macrophages
This enzyme enables pathogens to escape from phagolysosomes.
Phospholipase C
This toxin is cytotoxic for ciliated epithelial cells and disrupts mucociliary clearance.
Tracheal cytotoxin
This toxin causes localized tissue damage.
Dermonecrotic toxin
What is the function of pertussis toxin (PT)?
It activates an inhibitory G protein to increase adenylate cyclase activity. This result in increased mucous secretion. Inhibition of the G protein also disrupts signaling pathways.
What toxin increases cell permeability and induces apoptosis?
Vacuolating cytotoxin (VacA)
This enzyme degrades elastin.
Elastase
These enzymes rearrange actin and are cytotoxic for epithelial cells.
Exoenzymes S & T
