January 2, 2014

New Strain of C. botulinum Produces the World’s Deadliest Poison

by Zach Hartman

Marblebust of Cleopatra VII of Egypt form 30-40 BC

Marblebust of Cleopatra VII of Egypt form 30-40 BC

Poisons have long fascinated us both for their power and intrigue. For example, the story of the Egyptian ruler Cleopatra is told in a new exhibit at the American Museum of Natural History called “The Power of Poisons,” which highlights the role that poisons have played in history, literature, and medicine. Faced with the fall of her empire in Egypt to the Roman Caesar Octavian and the death of her lover Mark Antony, Cleopatra chose a slow, and possibly painful, death by provoking an Egyptian cobra until it bit her.

Scientists have recently added to our knowledge of poisons by identifying a new candidate as the most toxic substance known to man. This has long been the domain of botulinum toxin, a protein that is synthesized by different strains of the bacterium Clostridium botulinum. This bacterial species thrives in the soils of different regions around the world. It’s also famous for being the principal danger associated with improperly-canned foods, which is why it is highly dangerous to eat foods from damaged or swollen cans.

So what does this bacterium do that is so dangerous to humans? The bacteria produce a variety of toxins, called botulinum toxin A-G. The toxic protein is absorbed in the upper GI tract, where it can travel to the nerves that control muscle fibers. The nervous system relies on vesicles to deliver neurotransmitters that control muscle action. The toxin works by getting into cells and preventing the function of these vesicles. Failure of the vesicles means the nerve cannot transmit signals to the muscles, resulting in paralysis. The main cause of death due to botulinum poisoning is respiratory failure; since our lung function depends on the ability of the diaphragm muscles to move in a controlled manner.

But Clostridium botulinum has stepped up its game recently. Researchers from the California Department of Public Health have discovered a new strain of the bacterium that produces a novel toxin, botulinum toxin H. The new toxin can be lethal if inhaled at a dose as little as 13 nanograms, or 13 million times smaller than a single grain of sand. Arsenic, by comparison, must be present at a dose more than 75 million times as high to be lethal .

The new toxin has proven so problematic that the researchers are even having difficulty getting their results published. Given its extreme toxicity and the fact that they were unable to identify an antitoxins to the poison, the possibility of bioterrorism prompted the United States Centers for Disease Control and Prevention to limit the amount of information that could be presented in the Journal of Infectious Diseases. Notably, the protein sequence of the new toxin could not be revealed, lest it be reproduced by those who would use the toxin to harm others.

So what will become of the new botulinum toxin? It has the dubious honor of being deadliest poison in the world. Man has made use of botulinum toxin in the past with Botox treatments that have been used for cosmetic surgery. Can any good come of this new strain? Or will it simply remain one of the record-holding curiosities? Time will tell. In the meantime, you should definitely avoid any potential sources of contamination, like improperly-canned foods. You wouldn’t want to risk ingesting the world’s deadliest poison!

Zach Hartman

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Zach Hartman is a freelance medical writer specializing in educational writing. He received his PhD in biochemistry and molecular biology from West Virginia University in 2013, where he worked with the signaling protein SHP2 and its role in breast cancer. Now he covers a broad spectrum of topics.