Toxins

Question 1

Name the 5 types of toxins

Answer 1

Neurotoxins
Exotoxins
Endotoxins
Enterotoxins
Cytotoxins

Question 2

Neurotoxins are

Answer 2

toxins which affect the nervous system

Question 3

Endotoxins are

Answer 3

The LPS portion of gram negative cell walls

Question 4

Exotoxins are

Answer 4

Toxins released outside of the bacteria into host cells or tissue

Question 5

Entertoxins are

Answer 5

toxins which affect the small intestine

Question 6

Cytotoxins are

Answer 6

toxins which burst the infected cell open

Question 7

Describe the toxin produced by vibrio cholerea

Answer 7

The cholera toxin is an exotoxin which has an AB subunit structure. Once released by the vibrio cholerea cell the B subunits binds the toxin to ganglioside receptors of intestinal cells and the toxin enters the host cell by endocytosis. The A and B subunits seperate and the B subunits are released from the cell whilst the A subunit inhibits protein synthesis by ribosylating G-protein causing increased conversion of ATP to cAMP and leading to loss of nutrients and ions from the cell (which causes watery diarhhea).

Question 8

What bacteria produces the botulinum toxin

Answer 8

Clostridium botulinum

Question 9

Describe the botulinum toxin

Answer 9

The botulinum toxin is an AB type neurotoxin. The B subunit binds to presynaptic membranes of stimulatory motor neurons and mediates transfer of A subunit into the motor neuron. The A subunit cleaves and inactivates proteins involved in exocytosis this blocks the release of acytlcholine and leads to flaccid muscle paralysis.

Question 10

What bacteria produces the tetanus toxin

Answer 10

Clostridium tetani

Question 11

Describe the tetanus toxin

Answer 11

The tetanus toxin is an AB type neurotoxin. The toxin binds to neurons and is transported to the spinal cord where the B subunit binds to gangliosides of inhibitory neurons. Inhibitory neurons normally release GABA and Glycine to inhibit Acetylcholine release but the A subunit prevents exocytosis of GABA and Glycine. This leads to constant acetylcholine relase and permanently contracted muscles.

Question 12

How is the botulinum toxin treated

Answer 12

By administering antitoxin which neutralises unbound toxin in the patient

Question 13

How is the tetanus toxin treated

Answer 13

The tetanus vaccine stimulates production of neutralising antibodies