Question

Compare and contrast exotoxins and endotoxins with regard to their: a) chemical nature, b) source, c) effects on human body cells and resulting symptoms, and d) examples.

Answer 1

EXOTOXINS:

A) They are diffusible proteins (or polypeptides) secreted into the external medium by the pathogen

B) They are produced extracellularly by both Gram-negative and Gram-positive bacteria

C) The damage may be physiological, for example cholera toxin promotes electrolyte excretion from enterocytes without killing the cells, or pathological, where the toxin (for example diphtheria toxin) inhibits protein synthesis and induces cell death.

D) Well-known exotoxins include: botulinum toxin produced by Clostridium botulinum; Corynebacterium diphtheriae toxin, produced by diphtheria and tetanospasmin produced by Clostridium tetani.

ENDOTOXINS:

A) It is a lipopolysaccharide or lipo-oligosaccharide

B) It is a component of the outer membrane of Gram-negative bacteria

C) The presence of endotoxins in the blood is called endotoxemia. It can lead to septic shock, if the immune response is severely pronounced. Other systemic effects include fever and inflammation.

D) Toxins produced by E.coli, Salmonella Typhi, Shigella, Vibrio cholera