Botulinum Neurotoxins

Botulinum neurotoxins (BoNT), derived from the gram-positive, anaerobic bacterium Clostridium botulinum and closely related bacteria, are among the most lethal substances known to humans. BoNTs can cause a range of lethal human diseases,including botulism. BoNTs, also known as “neurotoxins”, disrupt the functioning of the neural pathways by blocking nerve signals from reaching muscles. This disruption results in a characteristic flaccid paralysis, or muscle weakness due to the inhibition of motor-neuron-initiated muscle contraction. Botulinum neurotoxins are divided into subtypes A, B, C1, D, E, F, and G, depending on the symptoms that they cause in laboratory animals. Type A is the most wide spread, while type B is the major cause of botulism in infants. Type C and Type D have been found in fish, while type E has sometimes been associated with botulism in humans. The C. botulinum bacterium produces and releases these neurotoxins, which can in turn be absorbed through the intestines, or potentially through broken skin. BoNT has recently gained a great deal of attention due to its use in medical treatment. Botulinum toxin is clinically used to treat both neurological and non-neurological disorders such as benign essential blepharospasm, strabismus, torticollis, overactive bladder, and facial tremors. It is also popularly used cosmetically to reduce wrinkles and treat excessive sweating. This use has been effective in temporarily reducing the patients’ symptoms, but may also cause negative side effects that can include dry mouth, headache, fatigue, nausea, blurred vision, droopy eyelids, and paralysis of the wrong muscles local to where the injection was made. In summary, botulinum neurotoxins have the potential to be lethal when produced and released by C. botulinum bacteria. BoNTs block nerve signals from reaching muscles, resulting in flaccid paralysis, and they are now used for both medical treatment and cosmetic uses, although there is a risk of adverse effects.