3.02 Bacterial Toxins

Microbiology review for the USMLE Step 1 Exam.

• Bacterial toxins are harmful compounds produced by bacteria that cause damage to the host
• Exotoxins are toxins that are actively secreted by some species of gram positive and gram negative bacteria
• Examples of exotoxins include botulinum toxin, Corynebacterium diphtheriae toxin, and cholera toxin
• Endotoxins are toxins that are contained within the cell wall of gram negative bacteria and are released when the bacteria are lysed or fragmented
• Structurally, endotoxins consist of the O antigen, the core oligosaccharide, and Lipid A, with the Lipid A component being responsible for most of the toxicity
• Endotoxins are less virulent and more heat stable than exotoxins, and are usually contained in the bacteria's own genetic material rather than on a plasmid