Unit 2 Exotoxins And Endotoxins Flashcards
Common to all gram-negative bacteria
Endotoxins
Composition: LPS of the cell envelope.
Endotoxins
Released when gram-negative cell is destroyed. (requires bacterial cell death for its release)
Endotoxins
Common to all gram-positive bacterla
Exotoxins
Released by the living bacteria (does not require bacterial cell death for its release)
Exotoxins
Can target specific host cells.
Can interrupt intracellular activities.
Can kill and help spread bacteria In tissues.
Exotoxins
Organism type
Gram-positive and Gram-negative
Exotoxins
Chemical nature
- Simple protein
Exotoxin
Chemical nature
Protein-lipid-
polysaccharide
Endotoxin
Stability to heating
- Stable
Endotoxin
Stability to heating
- labile
Exotoxin
Detoxification by
formaldehyde
- detoxified
Exotoxins
Detoxification by
formaldehyde
- not detoxified
Endotoxin
Neutralization by
homologous antibody
- Complete
Exotoxins
Neutralization by
homologous antibody
- Partial
Endotoxins
Biological activity
- individual to toxin
Exotoxins
Biological activity
- Same for all toxins
Endotoxins
Polypeptides with a molecular weight of 10,000-900,000
Exotoxins
Highty antigenic: stimulate formation of high-titer antitoxin; antitoxin neutralizes toxin
Exotoxin
Converted to antigenic, nontoxic toxoids by formalin, acid, heat.
and so on; toxoids are used to immunize
Exotoxins
Usually bind to specific receptors on cells
Exotoxins
Usually do not produce fever in the host
Exotoxins
Frequently controlled by extrachromosomal genes
(eg, plasmids)
Exotoxins
Lipopolysacchäride complexes; lipid A portion probably responsible for
toxicity
Endotoxins
Relatively stable; withstand heating at temperatures above 60°C for hours
without loss of toxicity
Endotoxins
Weakly immunogenic; antibodies are antitoxic and protective; relationship
between antibody titers and protection from disease is less clear than
with exotoxins
Endotoxins
Not converted to toxoids
Endotoxins
Moderately toxic fatal for animals in tens to hundreds
Endotoxins
Specific receptors not found on cells
Endotoxins
Usually produce fever in the host by release of interleukin-1 and other mediators
Endotoxins
Synthesis directed by chromosomal genes
Endotoxins
