Toxins

Question 1

Six toxin classifications

Answer 1

Help with tissue spread
Damage cellular membranes
Stimulate cytokine production
Inhibit protein synthesis
Toxins modify intracellular signaling pathways
Inhibit release of neurotransmitters

Question 2

Toxins which facilitate spread through tissues

Answer 2

hyaluronidase, collagenase, elastase, deoxyribonuclease, streptokinase

Question 3

Toxins damaging cellular membranes

Answer 3

hemolysins
cytolysins -> form pores
degradation of specific membrane components

Question 4

Toxins which stimulate cytokine production

Answer 4

Superantigens/pyrogenic exotoxins

• erythrogenic toxin of S. pyrogenes
• enterotoxins and TSST-1 of S. aureus
• scarlet fever, TSS, food poisoning

Question 5

Toxins which inhibit protein synthesis

Answer 5

Diphtheria toxin and P. aeruginosa exotoxin A
Shiga toxins (Shigella dysenteriae and E. coli)

Question 6

Toxins which modify intracellular signaling pathways

Answer 6

Heat labile toxins from V. cholerae and E. coli
Pertussis toxin
Heat stable enterotoxin-I of E. coli
Anthrax edema factor (B. anthracis) and adenylate cyclase toxin (B. pertussis)
Anthrax lethal factor
C. difficile toxins A and B

Question 7

Toxins which inhibit neurotransmitter release

Answer 7

Botulinum toxin

Tetanus toxin

Question 8

Mechanism of action of staph aureus and strep pyrogenes

Answer 8

cytokine interference -> super antigen

Question 9

Mechanism of action of Diphtheria and Pseudomonas aruginosa exotoxin A

Answer 9

protein synthesis inhibition
inactivation of EF-2
ADP ribosyltransferases
NAD to modified histidine on EF-2

Question 10

Mechanism of action of Shiga toxin (S. dysentariae and E. coli) and plant toxin ricin

Answer 10

Protein synthesis inhibition
RNA N-glycosidases
remove particular adenine from 60S subunit -> ribosome inactivation

Question 11

Mechanism of heat labile V. cholerae and E. coli toxins

Answer 11

Cell signaling pathway modification
ADP ribosyltransferases -> increase membrane assoc. adenylate cyclase activity
activates alpha subunit of stimulatory G reg protein
increased intracellular cAMP

Question 12

Mechanism of pertussis toxin

Answer 12

Cell signaling pathway modification
ADP ribosyltransferase -> increase membrane assoc. adenylate cyclase activity
inactivates alpha subunit of inhibitory G-reg protein
increased intracellular cAMP

Question 13

Mechanism of heat-stable enterotoxin-I of E. coli

Answer 13

Cell signaling pathway modification
activation of membrane assoc. guanylate cyclase
increased levels of cGMP

Question 14

Mechanism of anthrax edema factor (B. anthracis) and adenylate cyclase toxin (B. pertussis)

Answer 14

Cell signaling pathway modification
adenylate cyclases -> cause increase in cAMP
require calmodulin and calcium

Question 15

Mechanism of anthrax lethal factor

Answer 15

Cell signaling pathway modification

endopeptidase, cleaves MAP kinase kinase, inactivates function of pathway

Question 16

Mechanism of C. difficile A and B

Answer 16

Cell signaling pathway modification
glucosyl transferases -> alter actin cytoskeleton
UDP-glucose to several Rho family GTPases

Question 17

Mechanism of botulinum toxin

Answer 17

Neurotransmitter release
Myoneuronal junction -> Ach release inhibition
flaccid paralysis

Question 18

Mechanism of tetanus toxin

Answer 18

Neurotransmitter release
Inhibits release of Ach from inhibitory neurons
spastic paralysis

Question 19

Zinc dependent enteropeptidases

Answer 19

cleave SNARE proteins

botulinum and tetanus toxins