Microbial Toxins Flashcards
7 most deadly chemical substances (poisons)
*Botulinum toxin A — Clostridium botulinum
*Tetanus toxin A — Clostridium tetani
*Diphtheria toxin— Corynebacterium diphtheriae
Dioxin— man made
Muscarine— Amanita muscaria
Bufotoxin— Genus Bufo
Sarin— man made
Exotoxins
High molecular weight
Extracellular proteins
Antigenic
Heat Labile
Soluble in body fluids
Single bacterium can produce multiple exotoxins
Exotoxins classification
Site of action
Mode of action
Biochemical target
Toxin structure
Exotoxins classification by site of action
Type 1 toxins— act extracellularly
Type 2 toxins— act on eukaryotic cell membranes
Type 3 toxins — have intracellular targets
Superantigens
Type 1 exotoxin
Can induce more T cells and release much more cytokines
Ex: S.aureus toxic shock syndrome toxin
Type 2 exotoxins
Destroy the integrity of the mammalian cell membrane
Cause cell lysis
Called as lytic factors or pore-forming cytotoxins
Type 3 exotoxins
A-B type toxins
Act on intracellular target
2 functional components: Enzymatic component (A), Binding component (B)
Intracellular targets of A parts of Type 3 exotoxin
Protein synthesis
Signal transduction
Cytoskeleton
Cellular trafficking
Exotoxin classification by mode of toxic action
Cytotoxins
Enterotoxins
Neurotoxins
Which bacterial toxin causes food poisoning
Enterotoxins
2 bacterial neurotoxins
Botulinum toxin
Tetanus toxin
Botulinum toxin mechanism
Inhibits ACh release
Inhibits nerve impulses
Muscle become inactive
Flaccid paralysis
Tetanus toxin mechanism
Inhibits glycine/ GABA release
Inactivates inhibitory neurons
Muscle over-active
Spastic paralysis
Endotoxins
Cell-bound
Released in large amounts only when bacterial cells are lysed
Lipid A
Heat stable
Weakly immunogenic
Strongly mito genie for B lymphocytes
Endotoxins causes
DIC= Disseminated Intravascular Coagulation. endotoxins activate blood-clotting proteins and cause formation of small blood clots
Fever= endotoxins stimulate by directly or indirectly
