Bacterial Toxins & Enzymes

Question 1

These exotoxins non-specifically activate T cells and cause overwhelming cytokine secretion.

Answer 1

Superantigens -

S. pyogenes exotoxin A

S. aureus TSST-1 & Enterotoxin Type B

Question 2

What is the function of exfoliating toxins (ETA & ETB)?

Answer 2

Serine proteases that cleave a desmosomal protein in keratinocytes that hold cells together.

Question 3

Hyanuronidase

Answer 3

Cleaves hyaluronic acid in the epithelial cell matrix to facilitate tissue penetration.

Question 4

This toxin is phospholipase and targets cholesterol in the cell membrane. The toxin is directly responsible for gas gangrene and myonecrosis.

Answer 4

Clostridium perfringens alpha toxin

Question 5

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.

Answer 5

Pyrogenic exotoxins (Spe toxins)

Question 6

This toxin disrupts the membrane by creating pores and causing hemolysis.

Answer 6

S. aureus alpha toxin

Question 7

True or False. Hemolysins lyse lymphocytes.

Answer 7

False. Hemolysins lyse red blood cells.

Question 8

This bacterial enzyme degrades neuraminic acid (sialic acid) in the intracellular cement of the epithelial cells of the intestinal mucosa.

Answer 8

Neuraminidase

Question 9

What toxins act on EF2 to inhibit protein elongation and ultimately cell death?

Answer 9

Diphtheria toxin & Exotoxin A

Question 10

What is the function of Listeriolysin O?

Answer 10

Acid activated, pore-forming cytolysin

Question 11

This toxin cleaves SNARE proteins that prevents release of GABA and causes spastic paralysis.

Answer 11

Clostridium tetani tetanospasmin

Question 12

Phospholipase

Answer 12

Breaks down phospholipids in the cell membrane

(ex: Clostridium alpha toxin)

Question 13

This bacterial enzyme converts plasminogen to plasmin, which digests fibrin and prevents blood clotting.

Answer 13

Streptokinase / Staphylokinase

Question 14

What toxin cleaves SNARE proteins, preventing release of Ach at the musculoskeletal junction, resulting in flaccid paralysis?

Answer 14

Clostridium botulinum toxin

Question 15

Lecithinase

Answer 15

Destroys lecithin in the cell membrane.

Question 16

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.

Answer 16

Pneumolysin

Question 17

This bacterial enzyme lyses phagocytes and their granules.

Answer 17

Leukocidin (Panton-Valentine Factor) / Streptolysin

Question 18

What gives G- bacteria their endotoxin ability?

Answer 18

Lipid A in the LPS outer membrane

Question 19

What enzyeme coverts H2O2 to H2O and O2 and is used to differentiate between staphylococcus from streptococci?

Answer 19

Catalase

Question 20

Collagenase

Answer 20

Breaks down collage in connective tissues to facilitate bacterial invasion.

Question 21

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.

Answer 21

Shiga Toxin & Shiga-like Toxin

Question 22

This protein is located in the cell wall of staphylococci and binds the Fc portion of IgG and inhibits opsonization of the bacteria.

Answer 22

Staphylococcal Protein A

Question 23

This enzyeme coverts fibrin to fibrinogen to form clots.

Answer 23

Coagulase

Question 24

This enzyme enables resistance to penicillin antibiotics.

Answer 24

Beta lactamase

Question 25

What is the mechanism of action of the Cholera toxin?

Answer 25

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.)

Question 26

What toxins are produced by B. anthracis and what are their functions?

Answer 26

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

Question 27

This enzyme enables pathogens to escape from phagolysosomes.

Answer 27

Phospholipase C

Question 28

This toxin is cytotoxic for ciliated epithelial cells and disrupts mucociliary clearance.

Answer 28

Tracheal cytotoxin

Question 29

This toxin causes localized tissue damage.

Answer 29

Dermonecrotic toxin

Question 30

What is the function of pertussis toxin (PT)?

Answer 30

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.

Question 31

What toxin increases cell permeability and induces apoptosis?

Answer 31

Vacuolating cytotoxin (VacA)

Question 32

This enzyme degrades elastin.

Answer 32

Elastase

Question 33

These enzymes rearrange actin and are cytotoxic for epithelial cells.

Answer 33

Exoenzymes S & T