Microbial toxins and Mycotoxins Flashcards
What are the two broad categories of microbial toxins?
Endotoxins
Exotoxins
What is microbial endotoxin?
Lipopolysaccharide specifically Lipid A positioned in cell membrane
Molecular structure recognised by pattern recognition receptors on host cells as a sign of bacterial infection
What does endotoxin detection cause?
Release of cytokines TNFalpha and IL-1 resulting in fever, hypotension, loss of effective circulation and many other pathophysiological effects
What are exotoxins?
Bacterial proteins usually released during bacterial growth
What are cytolytic toxins?
Exotoxin
Haemolysins or leukocidins
What are some examples of enzyme toxins?
Alpha toxin, hyaluronidase, collagenase, protease, lipase
What are ADP-ribosylation toxins?
Labile enterotoxin with 5 B subunits and 1 A subunit
Similar to cholera toxin and attaches to brush border of small intestinal cells
What is the pathomechanism of ADP-ribosylation toxin?
Causes increase in cAMP so chloride ion channel activated and chloride secretion increased so sodium and water are lost from tissue into lumen
What is the pathomechanism of botulinum toxin?
Blocks release of acetylcholine at the synapse and NMJ resulting in flaccid paralysis and death
What is the pathomechanism of tetanus toxin?
Blocks release of neurotransmitters for inhibatory synapses causing uncontrolled excitatory synapse activity and paralysis by constant tensing of muscles
What is the pathomechanism of superantigens?
Immunomodulators causing massive T cell activation and cytokine release Toxin binds to invariable regions on MHC class II on APC so the normal process of T-cell activation is short-circuited
What are three common mycotoxins?
Toadstool poisoning
Ingestion of plant pathogenic fungi
Ingestion of moulded feed
What does ergot poisoning cause?
Constriction of arterioles in extremities due to vasoactive alkaloids resulting in gangrene and lameness
Convulsions, hallucinations and pain also occur
What does alfatoxin poisoning cause?
Liver damage, tumours, teratogenic
Which fungi produce which toxins?
Aspergillus flavus = aflatoxin B
Apsergillus versicolor = sterigmatocystin
Pennicillium viridicatum = ochratoxin
Fusarium sporotrichoides = Trichothecenes (T-2)
Fusarium graminearum = Zearalanone
