Clostridium botulinum

Clostridium botulinum is a gram-positive, rod-shaped bacterium that produces neurotoxins, known as botulinum neurotoxins types A-G, that cause the flaccid muscular paralysis seen in botulism. It is the main paralytic agent in botox and is commonly found in soil.

It is also an obligate anaerobe, meaning oxygen is poisonous to the cells. Superoxide dismutase helps C. botulinum tolerate traces of oxygen. It was first recognized and isolated in 1895 by Emile van Ermengem. Subsequent outbreaks were always found to be anaerobic spore formers, so Bengston proposed that the organism be placed into the genus Clostridium as the Bacillus genus was restricted to aerobic spore forming rods.

Classification is based on the ability of the organism to digest complex proteins. DNA and rRNA studies support the subdivision of the species into groups I-IV. Group I and II are responsible for most outbreaks of human botulism. Improper canning and food that is improperly preserved can cause botulism poisoning.

Neurotoxing production is the unifying feature of the botulinum species. It is possible that the neurotoxin gene is subject to horizontal gene transfer, possibly from a viral source. Types A, B, E, and F cause disease in humans while types C and D infect animals but not humans. Some studies have shown that C. botulinum spores are prevalent in certain geographic areas.

A mouse bioassay is used to determine the type of C. botulinum in monoclonal antibodies. Real-time PCR is now used to accomplish this. It is used in some medicaments and in some “off-label” medical purposes. However, it is also believed to have the potential to be a bio-weapon.

It is a soil bacterium and the spores can survive in most environments. They can survive a boil at sea level thus many foods are canned with a pressurized boil to achieve a higher temperature. High levels of acid within the cans help to prevent growth of spores.