Botulism occurs in humans in three forms: Food Botulism, Infant Botulism, and Wound Botulism, depending on the portal of entry of the toxin produced by the bacterium. The bacterium grows only in oxygen-free conditions. It forms heat-resistant spores that are only killed at temperatures above 100 °C.
The toxins produced by the bacteria are extremely toxic: as little as 10 nanograms (ten billionths of a gram) are considered a lethal dose for humans. The toxins damage the nerve tissue, causing "flaccid paralysis". After twelve to 36 hours, nausea, diarrhoea or constipation occur. Typical are subsequently visual disturbances (double vision, blurred vision, photophobia), dysphagia as well as a rapidly progressing flaccid paralysis, which also affects the respiratory muscles.
It is not possible to tell by looking at food whether it contains germs, spores or toxins of Clostridium botulinum. However, so-called "bombages", i.e. canned foods that have been bloated by gas-forming clostridia, can provide an indication. If you have such bloated tins at home, they should not be opened under any circumstances, but disposed of or handed over to the official food control for examination.
As the botulinum toxins are heat-sensitive, they are inactivated in a few seconds during cooking after reaching an internal temperature of 100 °C in the food.
In the past, it often happened that spores of Clostridium botulinum survived the "preservation" of canned food and sprouted during storage. Today, therefore, the so-called "botulinum cook" is carried out on critical products during sterilisation in industrial food production: This involves heating the food at 121 °C for three minutes. This reliably kills all spores.
Caution is advised when preserving fruit or vegetables yourself in preserving jars at home: Without special technology, a temperature of 100 °C (boiling water) cannot be exceeded for physical reasons. When preserving fruit and vegetables, the food should therefore be heated to 100 °C twice - at least 24 hours apart - in order to kill any spores that may have sprouted.
Since bee honey can also contain spores of Clostridium botulinum, it is not recommended in some countries to give honey to infants (for example, to make the pacifier or the mother's breast more palatable to them if they are unable to suck): The infant's intestine does not yet have a stable intestinal flora, the spores can germinate in the infant's intestine, form toxins and lead to the so-called "infant botulism".
Situation in Austria
Botulism diseases are very rare: Since 2000, 38 cases have been reported in Austria.
The bacteria only become critical when they multiply and produce toxins. Foodstuffs that are stored under oxygen-free conditions and whose environment is only slightly acidic or neutral are primarily at risk, e.g. home-pickled vegetables/fruit or home-made preserves. In western industrialized countries, contamination of foodstuffs with botulinum toxins is extremely rare.
Dr. Christian Kornschober
- +43 50 555-61201