Clostridium botulinum

Clostridium botulinum

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Changed on: 10.04.2019
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Clostridium botulinum is an anaerobic bacterium, meaning that it only grows in an oxygen-free environment. It produces heat-resistant spores that are only destroyed at temperatures above 100 °C. The bacterium is found in soil and coastal waters worldwide. The neurotoxins produced by this pathogen are among the deadliest toxins known. The tetanus (lockjaw) agent is a member of the same family of bacteria.

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Clostridium botulinum is an anaerobic bacterium, meaning that it only grows in an oxygen-free environment. It produces heat-resistant spores that are only destroyed at temperatures above 100 °C. The bacterium is found in soil and coastal waters worldwide. The neurotoxins produced by this pathogen are among the deadliest toxins known. The tetanus (lockjaw) agent is a member of the same family of bacteria.

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Botulism in Austria

Three patients are currently being treated for botulism in Austria. Examinations for botulinum toxins are carried out at the National Reference Centre for Botulism at AGES. The diagnosis of the disease showed that there is no epidemiological connection between the patient from Styria and the other two cases in Vienna.  Home-pickled vegetables seem to have been the source of the infection in Styria.

The sources that caused the infections in Vienna could not be identified. Remaining samples of industrially produced, pickled vegetables, which were found in the refrigerator of the two infected individuals could be excluded as a source of infection. A search using the European early warning system Epidemic Intelligence System (EPIS) showed that only a few individual cases of food-borne botulism have been diagnosed in Europe. Austria is currently the only country with acute infections.

Botulism is poisoning caused by the bacterium Clostridium botulinum: the neurotoxins produced by this bacterium are among the most powerful toxins known. Botulism infections are very rare: only 20 cases have been reported in Austria since 2000. Botulism occurs in humans in three forms: food-borne botulism, infant botulism and wound botulism, depending on where the toxin has entered the body.

Food

Clostridium botulinum is a naturally occurring pathogen found in soil, sea and river beds, dust, water and the intestines of humans and animals. Food that comes into contact with any of these materials, such as soil or water, could be contaminated.

However, the bacteria only become critical once they start reproduction and produce toxins. Food stored in oxygen-free conditions and in an environment with only slightly acidic or neutral conditions  – e.g. home-pickled vegetables/fruit or home-made preserves – are the most likely to be affected. Contamination of food with botulinum toxins is very rare in Western industrial countries.

Prevention

There is no way to see whether food contains Clostridium botulinum germs, spores or toxins. However, swollen or bulging tins could be an indicator of contamination with Clostridium botulinum, as the swelling could be caused by gas-producing clostridia. Such tins should not be opened, but disposed of or handed to the appropriate food control agency for further examination.

Botulinum toxins are heat-sensitive and will be deactivated during the cooking process within seconds, once the food has reached a core temperature of 100 °C.

In the past, clostridium botulinum spores used to frequently survive the preservation process in tinning and could germinate during storage. As a result, a “Botulinum cook” is currently used for the sterilisation of critical products in industrial food processing: the food products are heated at 121 °C for three minutes. This is known to reliably kill off all spores.

It is important to be careful when preserving or pickling fruit or vegetables in preserving jars: a temperature of 100 °C (boiling water) cannot be exceeded for physical reasons without the use of special technology. Thus, the food should be heated to 100 °C twice, with a minimum interval of 24 hours, to kill off germinated spores, when preserving or pickling fruit and vegetables.

Given the fact that bee honey could also contain Clostridium botulinum spores, some countries advise against giving babies honey (to make the dummy or even the mother’s breast more interesting if they do not feed properly, for instance): a baby’s digestive system has yet to form stable intestinal flora, thus, the spores could germinate inside the baby’s gut, produce toxins and result in so-called infant botulism.


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