Microbial and Fungal Toxins Flashcards
WHat 2 types of microbial toxin exist?
> Endotoxin (LPS) - part of the outermembrane of G- bacteria - Lipid A part specifically (O some chains largely irrelevant) - heat stable - hydrophobic > exotoxins - secreted or released on lysis - proteins(so heat labile)
How is LPS toxic?
- molecular structure recognised by PRRs on macrophages etc. as a sign of bacterial infection
- macrophage receptors ocmplexes CD14, TLR4, MD2 cause release of cytokines TNFa[tumour necrosis factor], IL-1
- > fever, hypotension, and other pathophysiological effects
Give 7 examples of exotoxins
- cytolytic toxins
- enzymes
- enterotoxins
- neurotoxins
- superantigens
- ADP-ribosylation toxins
- Type 3 secretion systems
Give an examples of cytolytic toxins
- Heamolysins eg Streptolysin S (Strep equi)
- leukocidins e.g. APXIII of a. pleuropneumoniae
Give examples of enzymes
- phospholipase C of Clostridium. perfringens (alpha toxin)
- hyaluronidase
- collagenase
- protease
- lipase
e.g.. of enterotoxins
- act in the GIT
- ADP-ribosylation toxins - Latbile enterotoxin (LT) of E. COli (similar to cholera toxin, attaches brush border of SI cells, -> secretion of CL- (+ therefore Na+) -> secretory D+ via cAMP and G protein receptors)
eg. of neurotoxin
> Botulinum toxin
- blocks release of ACh at synapse and NMJ -> flaccid paralysis and death
- often source is a dead and rotting small animal in a bale of silage
wild fowl also get botulism (“limber neck”)
Tetanus toxin
- blocks release of NTs for inhibitory synapses (GABA and glycine)
- uncontrolled exitatory synaptic activity
Why is botulism a public health risk?
Gets into milk
What are super antigens?
- eg. staph aureus TSST-1
- immunomodulators, induce massive T-cell activation and cytokine release
- toxin binds to invariable regions on MHC Class 2 on APC
- > short circuiting of the normal T cell activation pathway
What are ribose transferases?
- add one/more ADP-ribose moieties to a protein
- affect cell signalling and gender regulation
- toxicity of cholera toxin, diphtheria toxin and enterotoxins
- may types of exotoxin act this way eg. pertussis toxin, pseudomonas exotoxin A, diptheria, cholera, E.Coli LT
Outline the pathogenesis of salmonella. Clinical signs?
- > bloody mucoid D+ +- septicaemia
- Type 3 secretion systems (Injectosomes)
- needle like structure used as sensory probe to detect eukaryotic cells and then secret proteins into cells
- exert effects that help pathogen to survive and evade the immune response (uptake into host cell blebosome) initiate apoptosis of host cell
- T3SS proteins = structural proteins (syringe) efector proteins (contents) and chaperonins (protectors) contained in the Salmonella Pathogenicity Island
Egs. of toxins used as vaccine agents
> neutrolising Ab production to the toxoid (formalin treated toxin)
- tetanus
- diptheria
- clostridial
- pasteurella osteolytic tocin (atrophic rhinitis)
- APX1,2,3
- Anthrax toxin
3 classes of mycotoxin?
- toadstool poisoning
- ingestion of plant pathogenic fungi (ergotism)
- ingestion of mouldy feed (mycotoxicosis)
What colour is amanita phalloides? COmmon name?
Orange
- death cap
What is ergotism? Clinical signs
- ergot poisoning
- sclerotium forms in grass and cereal
- ergots contain vasoactive alkaloids (eg. ergotamine)
- ingestion -> constriction of arterioles in extremitis -> gangrene and lameness, convulsions, halucinations and pain
