toxin

Examples of toxin in the following topics:

• Paralysis-Causing Bacterial Neurotoxins

  • In 1973, Alan Scott used botulinum toxin type A (BTX-A) in monkey experiments.
  • The heavy chain of the toxin is particularly important for targeting the toxin to specific types of axon terminals.
  • The toxin must get inside the axon terminals to cause paralysis.
  • Following the attachment of the toxin heavy chain to proteins on the surface of axon terminals, the toxin can be taken into neurons by endocytosis.
  • The light chain of the toxin has protease activity.

• Toxins

  • Some of the major types of toxins include, but are not limited to, environmental, marine, and microbial toxins.
  • Microbial toxins may include those produced by the microorganisms bacteria (i.e. bacterial toxins) and fungi (i.e. mycotoxins).
  • Mycotoxins are the classes of toxins produced by fungi.
  • The most potent toxin is AFB1 and it is associated with carcinogenic effects.
  • Describe the major toxin types (bacterial toxins and mycotoxins) and their mechanisms of action

• Diphtheria

  • The toxin can cause damage to the heart that affects its ability to pump blood or the kidneys' ability to clear wastes.
  • Diphtheria toxin is produced by C. diphtheriae only when it is infected with a bacteriophage that integrates the toxin-encoding genetic elements into the bacteria.
  • This signals the cell to internalize the toxin within an endosome via receptor-mediated endocytosis.
  • Inside the endosome, the toxin is split by a trypsin-like protease into its individual A and B fragments.
  • Corynebacterium diphtheriae produces toxins that can affect the skin by causing skin lesions, as shown here.

• Botulism

  • Botulism is a rare, but sometimes fatal, paralytic illness caused by botulinum toxin.
  • This toxin is a protein produced under anaerobic conditions by the bacterium Clostridium botulinum.
  • Botulinium toxin is one of the most powerful known toxins: about one microgram is lethal to humans.
  • Three main modes of entry for the toxin are known.
  • The bacterium then releases the toxin into the intestine, which is absorbed into the bloodstream.

• Staphylococcal Food Poisoning

  • Staphylococcal toxins are a common cause of food poisoning, as they can be produced in improperly-stored food.
  • Foodborne disease can also be caused by a large variety of toxins that affect the environment such as pesticides or medicines in food and naturally toxic substances such as poisonous mushrooms or reef fish.
  • Staphylococcus is a Gram-positive bacteria which includes several species that can cause a wide variety of infections in humans and other animals through infection or the production of toxins.
  • Staphylococcal toxins are a common cause of food poisoning, as they can be produced in improperly-stored food.
  • Toxins for bacterial infections are delayed because the bacteria need time to multiply.

• Direct Damage

  • Upon the use of host nutrients for its own cellular processes, the bacteria may also produce toxins or enzymes that will infiltrate and destroy the host cell.
  • Examples of bacteria that will damage tissue by producing toxins, include, Corynebacterium diphtheriae and Streptococcus pyogenes.
  • It produces a toxin, diphtheria toxin, which alters host protein function.
  • The toxin can then result in damage to additional tissues including the heart, liver, and nerves.

• Scarlet Fever

  • Scarlet fever is caused by an erythrogenic toxin, a substance produced by the bacterium Streptococcus pyogenes (group A strep. ) when it is infected by a certain bacteriophage.
  • Exotoxin A (speA) is probably the best studied of these toxins.
  • It is carried by the bacteriophage T12, which integrates into the Streptococcal genome, from where the toxin is transcribed.

• Pathogenicity Islands and Virulence Factors

  • Typical examples of PAIs are adherence factors, toxins, iron uptake systems, invasion factors and secretion systems.
  • Typical examples are adherence factors, toxins, iron uptake systems, invasion factors and secretion systems.
  • PAIs carry genes encoding one or more virulence factors, including, but not limited to, adhesins, toxins, or invasins.

• Tetanus

  • Tetanospasmin is an A-B toxin.
  • The other type of striated muscle, cardiac or heart muscle, is not affected by the toxin because of its intrinsic electrical properties.
  • This is due to the extreme potency of the tetanospasmin toxin; even a lethal dose of tetanospasmin is insufficient to provoke an immune response.Tetanus can be prevented by vaccination with tetanus toxoid.
  • A person infected with C. tetani can be treated with antibiotics, which will kill the multiplying bacteria but will have no effect on the endospores or the toxin.
  • To combat the effects of the toxin, tetanus immune globulin (TIG) antitoxin can be given to the patient.

• Biological Weapons

  • Biological warfare (BW) is the use of biological toxins or infectious agents with the intent to kill or incapacitate.
  • Biological warfare (BW) — also known as germ warfare — is the use of biological toxins or infectious agents such as bacteria, viruses, and fungi with the intent to kill or incapacitate humans, animals, or plants as an act of war .
  • There is an overlap between BW and chemical warfare, as the use of toxins produced by living organisms is considered under the provisions of both the Biological Weapons Convention and the Chemical Weapons Convention.
  • Toxins and psychochemical weapons are often referred to as midspectrum agents.