Microbial toxins and mycotoxins

Question 1

Lipid A causes release of what

Answer 1

cytokines (TNFα, IL-1)

Question 2

effect of cytokine release

Answer 2

fever, hypotension, loss of effective circulation, many pathophysiological effects

Question 3

types of exotoxins

Answer 3

Cytolytic toxins
Enzymes
Enterotoxins
Neurotoxins
Superantigens
ADP-ribosylation toxins
Type III secretion systems
Clostridial toxins

Question 4

Cytolytic toxin examples

Answer 4

Sometimes haemolysins e.g. Streptolysin S of Strep equi

Sometimes not haemolytic, but still damage cells; e.g. leukocidins + ApxIII of Actinobacillus pleuropneumoniae

Question 5

Enzymes examples

Answer 5

Phospholipase C of Clostridium perfringens = alpha toxin
hyaluronidase, collagenase, protease, lipase
can cause gangrene

Question 6

ADP-ribosylation toxins

Answer 6

labile Enterotoxin (LT) of E. coli.

Question 7

labile Enterotoxin

Answer 7

5 B subunits; 1 A subunit. 88 kDa protein
raises intracellular cAMP
causes release of Cl- from the cell
similar to cholera toxin

Question 8

Neurotoxins examples

Answer 8

Botulinum toxin

tetanus toxin

Question 9

Botulinum toxin - effect

Answer 9

blocks release of acetylcholine at the synapse and neuromuscular junction
Flaccid paralysis and death
can also affect water fowl

Question 10

tetanus toxin - effect

Answer 10

Blocks release of neurotransmitters for inhibitory synapses (glycine and GABA)
uncontrolled excitatory synaptic activity
Paralysis by constant tensing of muscles - tetani

Question 11

Superantigens - examples

Answer 11

Staphylococcus aureus TSST-1. 22 kDa protein.

Question 12

Superantigens - effects

Answer 12

Immunomodulators
induce massive T-cell activation & cytokine release.
binds to invariable regions on MHC Class II on APC - normal process of T-cell activation is short-circuited.

Question 13

protein toxins used effectively as vaccine antigens

Answer 13

Tetanus toxin
Diphtheria toxin
Clostridial toxins
Pasteurella Osteolytic toxin - atrophic rhinitis 
ApxI, II, III
Anthrax toxin

Question 14

Mycotoxins

Answer 14

Toadstool poisoning (e.g. death cap)
Ingestion of plant pathogenic fungi (Ergotism)
Ingestion of moulded feed (Mycotoxicosis)

Question 15

Ergotism or ergot poisoning

Answer 15

calviceps purperea
fungal sclerotium (black ergots) take the place of seeds
contains potent vasoactive alkaloids (ergotamine)
constriction of arterioles in extremities - gangrene + lameness

Question 16

Mycotoxicosis - aflatoxins

Answer 16

several different types
No antidotes, no neutralising substances, no antibody
Detection of toxin in feed now relatively easy.
Acute aflatoxin poisoning now rare but chronic poisoning continuing.
Young animals most susceptible.
Liver damage, tumours, teratogenic.

Question 17

Trichothecenes (T-2)

Answer 17

Grain moulded with Fusarium sp. in the fields.

alimentary toxic aleukia in humans

Question 18

Zearalanone (Oestrogenic factor, F-2)

Answer 18

Pigs, traced to mouldy grain.

Question 19

Ochratoxins

Answer 19

Denmark, pigs, nephritis.
Ochratoxin A from Aspergillus ochraceus
Coffee beans