The microorganism called Clostridium Botulinum produces the deadliest toxins known: the botulinum toxins. These toxins, designated letters from A to G, have gained a notorious identity over time. It is said that a mere thirty grams of pure toxin would be enough to kill every person in the United States. It sure is potent; even a small taste of contaminated food can cause full-blown illness and in some cases, immediate death. Naturally, these toxins have long been considered a threat as an agent of bioterrorism or biological warfare.
There are eight distinct toxin types (A, B, C1, C2, D, E, F, and G), and all of these except C2 are neurotoxins. These toxins are heat-labile, but once inside the gastrointestinal tract, it can form complexes with proteins and resist degradation. Toxin types A, B, E and F cause human disease; type G has been associated with sudden death, but not with neuroparalytic illness; and types C and D cause animal disease.
Botulism, a paralytic disease caused by these neurotoxins, can be classified into three types:
(1) food-borne botulism, from ingestion of preformed toxin in food contaminated by C. botulinum
(2) wound botulism, from toxin produced in wounds contaminated with the microbe
(3) intestinal botulism, from ingestion of the organism's spores and production of toxin the intestine of infants (infant botulism) or adults.
When absorbed in the body, the toxins interfere with the release of neurotransmitters called acetylcholine, which are responsible for signalling muscular contraction. This event results in the inability of the muscle cells to contract, and a slow but progressive paralysis spreads throughout the body. Eventually, the paralysis spreads to the respiratory muscles, resulting in respiratory failure and then death ensues. It is not an entirely hopeless case, however, as antimicrobial agents and antitoxins are now available to kill the causative agent and to counter the effects of the toxin.
But the botulinum toxins are not decidedly bad, after all. In the more recent years, scientists have developed the type A toxin into a useful agent, particularly as part of a cosmetic procedure to erase frown lines, crow's feet, and other facial wrinkles. Extremely small doses of Botox, which is purified type A botulinum toxin, may be injected into facial muscles that cause skin wrinkles, paralyzing or weakening them.
Some of the botulinum toxins have been approved for other therapeutic uses as well.
- The type A toxin has been approved for the treatment of strabismus, the inability of the eyes to maintain binocular vision due to an imbalance between eye muscles, and bleparospasm, a condition caused by involuntary spasmodic contractions of facial muscles surrounding the eye.
- The type B toxin has been approved for the treatment of cervical dystonia, a condition characterized by involuntary contraction of the neck muscles, causing abnormal movements and awkward posture of the head and neck.
More studies are being done which are aimed at investigating other uses of the botulinum toxins.