Microbial toxins and mycotoxins Flashcards
How do endotoxins affect the body?
its recognised by PRRs
it interacts with macrophages which causes a cytokine storm which results in a severe generalised inflammatory response
including activating the clotting cascade and inducing pyrexia
What is an endotoxin and how is it released?
lipopolysaccharide lipid A found in the outer membrane of gram neg bacteria
released when the bacteria lyses
How can endotoxins cause shock?
the cytokine storm, severe generalised infl. response, clotting cascade and pyrexia results in systemic vasodilation of the blood vessels which leads to a catastrophic fall in BP aka shock.
How does mannheimia haemolytica’s endotoxins damage tissue at the site of the infection?
LPA release in the lungs which stimulates the cytokine release and direct cell cytolysis to contribute to pulmonary lesions
Is endotoxic shock a risk with all bacterial infections?
no, endotoxic shock requires systemic release of the endotoxin (needs to be gram-) into the bloodstream which doesn’t happen in all infections.
Can antimicrobial therapy cause endotoxic shock?
yes, if bacteraemia (circulating bacteria) are present there is a high risk that AB therapy (especially bacteriocidal ABs that cause bacterial cell lysis) releases endotoxins into the bloodstream
What is the role of cytolytic toxins/enzymes?
they facilitate pathogenesis through digestion of host cells and tissues
often made to digest cells containing a vital nutrient for bacterial growth
How can we detect presence of haemolysis and what does this tell us?
in vitro on blood agar plates
presence is an indicator of a potentially more pathogenic bacterial species when interpreting culture results esp. when classifying streptococci
What is the role of leukocidins/leukotoxins?
cytolytic toxin/enzyme/exotoxin
primarily targetting WBC
ex: PVL produced by some strains of staph. aureus
Where is staph. aureus with PVL mainly found?
associated with community-acquired infections in humans
spillover from humans to pets they live with
PVL positive strains are more commonly found with deep tissue infections (vs soft tissue of non PVL strains)
implicated in necrotising pneumonia, necrotising fasciitis, musculoskeletal dz
What should we know about exotoxins that are also involved in generic cell and tissue damage in the body?
phospholipase, hyaluronidase, collegenase, protease, lipase
not necessarily a non potent toxins as they can potentially result in severe clinical signs
How can C. perfringens type A be detected in healthy GIT but is also known to cause necrotising enterocolitis in most animal species?
dysbiosis can result in proliferation and subsequent toxin release of phospholipase C
rapid destruction of healthy viable tissue
What are enterotoxins?
toxins implicated in the pathogenesis of the GI tract
implicated in infectious disease of animals and foodborne disease
ex: e. coli, staph. aureus, C. perfringens, bacillus cereus, etc.
How does the LT enterotoxin of e. coli act on the GIT?
its an adp-ribosylation toxin (adds an adp-ribose to a protein to disrupt cell signalling)
can attach to the microvilli of the small intestine
- labile toxin interacts with epithelial cell surface receptors
- a-subunit released into the enterocyte and interacts with G-protein
- g-protein with added adp-r leads to constitutive activation of adenylyl cyclase = no control of cAMP production
- increased cAMP activates chloride channels
- chloride secretion increases loss of sodium and water into the intestinal lumen = secretory diarrhoea
What are 2 examples of bacterial neurotoxins in vet med?
clostridium tetani: tetanospasmin = tetanus
clostridium botulinum: botulinum = botulism
