Microbial toxins and mycotoxins Flashcards
Lipid A causes release of what
cytokines (TNFα, IL-1)
effect of cytokine release
fever, hypotension, loss of effective circulation, many pathophysiological effects
types of exotoxins
Cytolytic toxins Enzymes Enterotoxins Neurotoxins Superantigens ADP-ribosylation toxins Type III secretion systems Clostridial toxins
Cytolytic toxin examples
Sometimes haemolysins e.g. Streptolysin S of Strep equi
Sometimes not haemolytic, but still damage cells; e.g. leukocidins + ApxIII of Actinobacillus pleuropneumoniae
Enzymes examples
Phospholipase C of Clostridium perfringens = alpha toxin
hyaluronidase, collagenase, protease, lipase
can cause gangrene
ADP-ribosylation toxins
labile Enterotoxin (LT) of E. coli.
labile Enterotoxin
5 B subunits; 1 A subunit. 88 kDa protein
raises intracellular cAMP
causes release of Cl- from the cell
similar to cholera toxin
Neurotoxins examples
Botulinum toxin
tetanus toxin
Botulinum toxin - effect
blocks release of acetylcholine at the synapse and neuromuscular junction
Flaccid paralysis and death
can also affect water fowl
tetanus toxin - effect
Blocks release of neurotransmitters for inhibitory synapses (glycine and GABA)
uncontrolled excitatory synaptic activity
Paralysis by constant tensing of muscles - tetani
Superantigens - examples
Staphylococcus aureus TSST-1. 22 kDa protein.
Superantigens - effects
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.
protein toxins used effectively as vaccine antigens
Tetanus toxin Diphtheria toxin Clostridial toxins Pasteurella Osteolytic toxin - atrophic rhinitis ApxI, II, III Anthrax toxin
Mycotoxins
Toadstool poisoning (e.g. death cap)
Ingestion of plant pathogenic fungi (Ergotism)
Ingestion of moulded feed (Mycotoxicosis)
Ergotism or ergot poisoning
calviceps purperea
fungal sclerotium (black ergots) take the place of seeds
contains potent vasoactive alkaloids (ergotamine)
constriction of arterioles in extremities - gangrene + lameness
Mycotoxicosis - aflatoxins
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.
Trichothecenes (T-2)
Grain moulded with Fusarium sp. in the fields.
alimentary toxic aleukia in humans
Zearalanone (Oestrogenic factor, F-2)
Pigs, traced to mouldy grain.
Ochratoxins
Denmark, pigs, nephritis.
Ochratoxin A from Aspergillus ochraceus
Coffee beans
