Botulism pathophysiology

Overview
The video presented here is of Botulinum toxin B and provides a general overview of the cause of Botulism. It describes the mechanism action that the toxin takes within the nerve cells.

Microbiology
Clostridium botulinum is an obligate anaerobe that forms spores. The natural habitat for the Clostridium botulinum spores is the soil. The species of Clostridium botulinum is made up of 4 genetically diverse groups that do not have much in common other than the fact that they all produce the botulinum toxin. The botulinum toxin itself exists as 7 different antigenic types and these 7 antigenic types have been assigned a series of letters: A, B, C, D, E, F, G. These toxins have a specific definition, and they are defined by their inability to cross neutralize the other types. For example, Anti-A toxin can not neutralize any of the other toxin types (B-G). It should be noted that Clostridium baratii and Clostridium butyricum can also produce the botulinum toxin.

The botulinum molecule itself is composed of a heavy chain as well as a light chain polypeptide. It is referred to as a dichain polypeptide. The light chain of the toxin contains an endopeptidase that blocks acetylcholine-containing vesicles from being able to fuse with the membrane at the end of the motor neuron. If acetycholine is not present, it will result in flaccid muscle paralysis.

Many people may not realize it, but the commercial therapeutic procedure termed "Botox" actually contains the botulinum toxin. However, there is a very small amount of it present, otherwise it would present an extensive danger. A vial of type A preparation, which is currently licensed in the US, contains only about 0.005% of the lethal oral dose and 0.3% of the lethal inhalation dose.

Clostridium botulinum is divided into 4 groups:


 * Group I - can produce toxins specifically A, B, or F proteolytic


 * Group II - can produce toxins specifically B, E, or F, nonproteolytic


 * Group III - can produce toxins C or D


 * Group IV - can produce toxin G but toxin G has not been shown to cause neuroparalytic illness.