Botulinum Toxin

Clostridium botulinum is a spore-forming bacterium. Like the well-known anthrax bacillus, the spores of Clostridium botulinum can persist in the environment for many years and, when conditions become more favorable (i.e., in a wound, food, and the lungs) the spore can germinate and free the toxin.

There are at least seven structurally different versions of botulinum toxin. The type designated as type A is responsible for some botulism food-borne outbreaks in the United States and elsewhere. Improperly canned foods are a particular threat.

Botulinum toxin is among the most poisonous substances known in the natural world. The toxin, which can be ingested or inhaled, and which disrupts transmission of nerve impulses to muscles, is naturally produced by the bacterium Clostridium botulinum. Certain strains of C. baratii and C. butyricum can also be capable of producing the toxin.

Botulinum toxin acts by preventing the transmission of nerve signals between the nerves that connect with muscle cells. Progressive functional deterioration of the affected muscles occurs. Symptoms of botulism intoxication include dizziness, blurred or double vision, nausea, vomiting, diarrhea, and weakness of muscles in various areas of the body. The muscle failure can be so severe as to lead to coma and respiratory arrest. Even in those who survive exposure to the toxin, complete recovery can take months.

The damage and lethality that can be inflicted by the toxin makes this agent important in forensic science. If botulism toxin poisoning is suspected, a forensic scientist can check for the presence of the bacterial spores.

The sometimes deliberate use of the toxin is also forensically relevant. Contamination of food is one route for infection with the toxin. This can occur naturally, via the bacterial contamination of the food. On the other hand, food can be deliberately contaminated. As well, the toxin can also be released into the air. The latter is invariably deliberate. For example, on at least three occasions between 1990 and 1995, while experimenting with biological warfare agents, the Japanese cult Aum Shinrikyo released botulinum toxins, but failed in attempts to spread them.