Chapter 8

BACTERIAL TOXIN AND ANTITOXINBacterialtoxins are by-products produced by pathogenic microbes that have taken up residence in the body.Bacteriumcan enter a host by various means, such as consuming contaminated food or water. Bacteria can also be introduced through mucous membranes, either by direct contact with the source or as a consequence of breathing in air-borne bacteria. The type ofbacterialtoxins released depends on the species of invading bacteria.

TOXINEndotoxins are compounds found in the cell walls of Gram negative bacteria. These compounds help to form a semi-permeable membrane which is designed to protect bacteria from threats. Once the bacteria die, the endotoxins are released, and many of these toxins cause health problems in people, animals, and other organismsENDOTOXINBoth Gram-positive and Gram-negative bacteria produce exotoxinsSome quite poisonous. For example, tetanus is caused by a bacterialtoxinproduced byClostridium tetanithat acts as aneurotoxin.EXOTOXINAnexotoxincan be classified by the types of tissues it targets, like neurotoxins that target neurons and enterotoxins that are designed to assault the digestive tract. Using anexotoxin, a microorganism can attack remote areas, rather than needing to be in direct contact with the targeted tissue.

EXOTOXIN cont..

PropertyExotoxinEndotoxinChemical propertiesProteinsExcreted by certain gram +ve or gram-ve bacteriaLipopolysaccharide-lipoprotein complexesReleased on cell lysis as part of the outer membrane of gram-ve bacteriaMode of action; SymptomsSpecificBinds to specific cell receptors/structure: cytotoxinGeneralFever, diarrhea, vomitingToxicityHighly toxic- fatalWeakly toxic rarely fatalImmunogenicityHighly immunogenic; stimulate the production of antitoxinPoor immunogen; immune response not sufficint to neutralize toxinProperties of exotoxins and endotoxinsANTITOXINAnantitoxinis a specializedantibodyor group ofantibodiesthat has the ability to neutralize a particular toxicant, a type of toxin produced exclusively by living organisms. Theantitoxinis also produced in living organisms, which includes plants, animals, and humans.The activity of anantitoxinis similar to that of a vaccine in that the organismsimmune systemis stimulated to produce a specific antitoxinin response to the presence of small amounts of a corresponding toxin.