Microbial Toxins

Question 1

Microbial Toxin

Answer 1

Macromolecular products of microbes that cause harm to susceptible animals by altering cellular structure or function

Question 2

List diseases caused directly by microbial toxins

Answer 2

Botulism, cholera, diptheria, whooping cough, scalded skin syndrome, scarlet fever, tetanus, toxic shock syndrome

Question 3

Explain how a microbial toxin is implicated in pathogenesis of an infectious disease.

Answer 3

1. ) show that purified toxin symptoms = infection syndromes
2. ) Show that antitoxin works
3. ) Show that virulence is proportional to toxin concentration
4. ) Show that nontoxinogenic mutants are avirulent

Question 4

Bacterial Protein Toxin

Answer 4

Originally called exotoxins

Some are excreted into extracellular space, some are released upon lysis

Question 5

Lipopolysaccharides (LPS)

Answer 5

From Gram (-)
PAMP that elicits host response
Low dose- fever and inflammation
High Dose- Shock and DIC
Mediated by cytokines

Question 6

Toxins that facilitate spread of microbes through tissues

Answer 6

Can break down ECM or debris in necrotic tissue

Question 7

Toxins that damage cellular membranes

Answer 7

Called hemolysins, but also cytolysins. Work by killing cells via pore formation or membrane disruption.

Question 8

Toxins that stimulate cytokine production

Answer 8

Pyrogenic exotoxins, basically superantigens

Question 9

Toxins that inhibit protein synthesis

Answer 9

Irreversible and causes cell death

Question 10

Diphtheria Toxin and P. aeruginosa exotoxin

Answer 10

Inactivate Elongation factor-2. Both are ADP ribosyltransferases (ADP-ribose transfer)

Question 11

Shiga toxins of Shigella dysenteriae and E. coli, and Ricin

Answer 11

RNA n-glysosidases, inactivating ribosomes

Question 12

Vibrio cholerae and E. coli heat-labile enterotoxins

Answer 12

ADP ribosyltansferases that increase cell-membrane associated adenlyate cyclase activity by activating alpha subunit

Increase cAMP in GI = choloride secretion = diarrhea

Question 13

Pertussis Toxin

Answer 13

ADP ribosyltransferase inactivates alpha subunit of g-proteins

Question 14

Heat-stable enterotoxin I of E. coli

Answer 14

Activates membrane gaunylate cyclase, increases celular cGMP concentrations

Question 15

Anthrax Edema Factor (EF) or Bacillus anthracis and adenylate cyclase toxin of bordetella pertussis

Answer 15

Aneylate cyclases that increase [cAMP]

Requires calmodulin and calcium to activate

Question 16

Anthras Lethal Factor (LF)

Answer 16

Cleaves MAP kinase kinase proteins, inactivating them

Question 17

C. diff A and B toxins

Answer 17

gluosyl transferases that inactivate GTPases, altering the actin cytoskeleton

Question 18

Botulinum toxin

Answer 18

Flaccid paralysis, inh acetylcholine release

Question 19

Tetanus toxin

Answer 19

sustained muscular contractions (spastic paralysis), inh release of neureotransmitters from inh interneurons in spinal cord

Question 20

Zinc dependent endopeptidases

Answer 20

Both tetanus and botulinum, inactivates SNARE complexes for exocytosis

Question 21

Intracellular Toxins

Answer 21

Usually have an a (active) and B (binding) subunit
Uses normal membrane constituents as receptors
Enters cell via endocytosis

Question 22

Antitoxins

Answer 22

Bind to toxins and neutralizes then (can’t reverse effects though)

Question 23

Toxoid

Answer 23

Toxin derivative that has immunogenicity but no toxicity