Microbial toxins and mycotoxins Flashcards
Endotoxin
LPS - specifically Lipid A
Causes release of cytokines
Endotoxin - clinical signs
fever, hypotension, loss of effective circulation
types of Exotoxins
bacterial proteins Cytolytic toxins Enzymes Enterotoxins Neurotoxins Superantigens ADP-ribosylation toxins Type III secretion systems Clostridial toxins - botulinum toxin
Cytolytic toxin - examples
Sometimes haemolysins - Streptolysin S of Strep equi
Sometimes not haemolytic, but still damage cells - leukocidins, ApxIII of Actinobacillus pleuropneumoniae
Enzymes - examples
Phospholipase C of Clostridium perfringens = alpha toxin
hyaluronidase, collagenase, protease, lipase
LT (labile toxin)
Similar to Cholera toxin.
Attaches to brush border of small intestinal cells
activates Cl channel - Na + water follow Cl out of cell
Neurotoxins
Botulinum toxin - blocks release of acetylcholine
at the synapse and neuromuscular junction.
Flaccid paralysis and death.
Tetanus toxin
Blocks release of neurotransmitters for inhibitory synapses - uncontrolled excitatory synaptic activity.
Paralysis by constant tensing of muscles - tetani.
Superantigens
Staphylococcus aureus TSST-1 protein.
Immunomodulators - induce massive T-cell activation &
cytokine release.
Toxin binds to invariable regions on MHC Class II on APC;
the normal process of T-cell activation is short-circuited.
Mycotoxins
Toadstool poisoning
Ingestion of plant pathogenic fungi (Ergotism)
Ingestion of moulded feed (Mycotoxicosis)
Ergotism or ergot poisoning
Sclerotium forms in grass & cereal
Ergotism or ergot poisoning - clinical effect
contain vasoactive alkaloids
constriction of arterioles in extremities → gangrene &
lameness. Also convulsions.
Halucinations & pain in humans
