Clostridium botulinum

The bacterium Clostridium botulinum (family clostridiaceae ) is found in soil , water sediments, plants and in the digestive tract of humans and animals. The gram-positive bacterium grows anaerobically, which is why it is often found in vacuum stored food. Unfortunately, the protein-rich and pH-adjusted environment within meat products is perfect for Clostridium botulinum to grow. The term botulinum derives from the Latin word for sausage: botulus . The oval spores of C. botulinum are heat-resistant up to 100°C and can be reactivated even after decades (spores are used for reproduction). Clostridium botulinum measures 2–10 µm (length) and 0.5–1.0 µm in diameter. The structure of Clostridium botulinum resembles that of Clostridium tetani .

What about botulism? Botulism, caused by Clostridium botulinum, or – more precisely – by its toxin (botulinum toxin), is the most dangerous food poisoning for humans, and often fatal (death rate: 10 – 50 %). Most years roughly 24 Germans will fall sick with food botulism. The symptoms occur between 2 and 36 hours after consumption ; including vomiting , nausea , diarrhoea, abdominal cramps, difficulties in swallow-ing, as well as impaired speech and vision. Death is caused by respiratory paralysis . To prevent food from being contaminated packed goods must be constantly cooled, and canned goods should be well heated twice.

Another type of botulism is “wound botulism” which predominantly occurs in combination with intravenous drug use. There, Clostridium botulinum sprouts in anaerobic sections of an injury. Clostridium botulinum can spread throughout the intestines of babies due to their different gut flora and because infants produce too little gastric acid, resulting in a type of botulism that older humans do not get. Babies should, therefore, not be allowed certain foods, e. g. honey.

How is botulism diagnosed? Botulism is diagnosed by molecular genetic procedures (e. g. quantitative multiplex-PCR). Cultivating Clostridium botulinum is only done in exceptional circumstances (in the case of baby botulism or wound botulism) and plays no role in diagnosing food botulism. Botulism is registrable for the purpose of immobilizing the source.

How is botulism treated? Emergency aid includes stabilisation of the cardiovascular functions and flushing of the gastro-intestinal tract. Nevertheless, the most efficient treatments for botulism are antitoxins. These primarily include antibodies cultivated from horses that specifically bind to the toxic protein, thus , inhibiting its efficacy. Due to possible allergic reactions to this horse product, the antiserum is treated with the enzyme pepsin .

What is the bacterium known for? Its notoriety derives from the so-called “botulinum toxins”, which are among the most potent known toxins. These neurotoxic proteins are built and secreted by Clostridium botulinum, and are therefore exotoxins. Some of the toxins are inactivated at a heat of 80 °C, and some only at 112 °C. The lethal oral dose for a human weighing 70 kg is 70 µg.

How are botulinum toxins structured and how do they function? The paralysing neurotoxin is surrounded by a non-toxic complex of bacterial-origin proteins. These bind to the presynaptic membrane of neurons and protect the toxin from stomach acids. However, they then dissociate in pH-adjusted milieu or body heat, setting the neurotoxin free. The toxin functions by breaking down membrane proteins, which irreversibly destroys the neuron. Then, the synaptic vesicles are unable to fuse with the membrane and distribute the neurotransmitter into the synaptic cleft. This then not only leads to the disturbance of the vegetative nerve system, but also to muscle weakness and even impares the lung function. Five of the nine different types of botulinum bacteria are pathogens for humans, others are only pathogenic for animals.

How can the toxins be utilised? The most popular use for processed botulinum toxin (“botox”) is in cosmetics to eliminate wrinkles and tighten the skin. To that end, botulinum toxin is injected into the target parts of the face or body causing muscle paralysis for three to six months. The first compounds of “botox” were approved in 2002. The increased usage for aesthetic purposes was harshly criticised because it required an increased amount of (incredibly cruel ) animal testing. Now, animal testing for cosmetic purposes is prohibited within the EU. Another use for botulinum toxins is in the treatment of dystonia and hyperhidrosis . Whenever pharmaceutical companies are developing a new medicine including botulinum toxins, they also have to keep the War Weapons Control Act in mind because botulinum toxin is considered the sixth most dangerous bioweapon.

EXERCISE: 1. A very popular use for botulinum toxin is in cosmetics.

a) True b) False

2. Clostridium botulinum is found in:

a) Soil b) Food c) Water d) The throat of human beings e) Plants

3. Clostridium botulinum is a gram-positive, spore building, anaerobically growing bacterium.

a) True b) False

You’ll find the answer on the next page

BIBLIOGRAPHY 1. http://dict.leo.org. 2.www.dict.cc. 3. www.nature.com. 4. www.rki.de. 5. www.webster-dictionary.org.

CARMEN LOBITZ Carmen Lobitz ist freie Trainerin, Lehrerin und MTA. Sie gründete 1998 in Berlin lobitz seminare, die unter anderem Englischseminare für Health Professionals anbieten. Kontakt: mail@lobitz-seminare.de www.lobitz-seminare.de

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Clostridium botulinum

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