Neurons: Victims of Bacterial Toxins

Bacterial Toxins & Damage to Neurons

Which bacterial toxins have negative impacts on the human body? This paper reviews those toxins and their effects on human functions.

Clinical Diseases

Professor F.H. Kayser explains that "Exotoxins" are pathogenic bacteria that are capable of producing a "variety of toxins that are either the only pathogenic factor" in the onset of diseases like diphtheria, tetanus and cholera, or if they aren't the only factor they are at lease a "major factor" in a person getting these three diseases (Kayser, 2011). Not all of these toxins attack the cells; cytotoxins, for example, can produce toxic effects in a number of different host cells, Kayser explains on page 15. But without fail, neurotoxins impact the neurons of the host, according to the author.

Kayser explains that AB toxins bind to "specific surface receptors on target host cells," and he lists the various AB toxins that do attack cells and neurons in those cells. Diphtheria toxin is an AB toxin, and it can lead to "cell death" through protein synthesis (Kayser, 16). The clinical reality associated with the diphtheria toxin is that it kills mucosal cells, which causes severe damage to the muscles of the heart, to kidneys, to adrenal glands, the liver and to "motor nerves of the head" (Kayser, 16).

The Cholera toxin is an AB toxin, and as it enters the body it attacks the ADP-ribosyl (that regulates protein G), and this results in the "permanent activation of this enzyme" which in turn results in an increase in the secretion of electrolytes (Keyser, 16). The ultimate result is a condition the author describes as "massive watery diarrhea" and a substantial loss of water and electrolytes (16).

The tetanus toxin directly attacks the neurons (synapses), preventing them from producing the "synapses of the interior horn" which in normal situations transmits inhibiting impulses to the motor nerve terminal" (Kayser, 16).

Meanwhile in the book Neurobiology of Brain Disorders: Biological Basis of Neurological and Psychiatric Disorders, the authors explain that the release of toxins can have a negative impact on the human nervous system. In particular the authors mention the "Clostridium botulinus and tetani toxins, which are metalloproteases that inhibit synaptic vesicle release" (Zigmond, et al., 2014). Those difficult words basically mean that the human body's neurons are disrupted by the tetanus toxin (as mentioned in the previous page) and by the botulinum (associated with the term botulism).

Once the botulinum toxin enters the human body, it spreads quickly via the bloodstream to negatively impact the "open-ended axon terminals of motor neurons"; in effect, the botulinum toxin blocks the normal synaptic vesicle release -- which results, Zigmond explains, in "flaccid paralysis" (436). One main concern that is shared by medical professionals is that drug addicts are known to use dirty needles, and botulism can result from the injection of "bacterial spores" (Zigmond, 436).

As for the tetanus toxin, it spreads from an open wound in a muscle and is transported "retrogradely within carrier vesicles to motoneuron cell bodies"; from there it somehow escapes being degraded and continues along a path that leads it to block the release of synaptic vesicles that are located in "inhibitory neurons" (Zigmond, 436). The result of the blockage of synaptic vesicles in the neurons can be seen in "tetanic spasms," the author explains.