A recent note from the Istituto Superiore di Sanità (ISS) highlights that Italy is the European country with the largest number of cases of botulism. 342 cases, between 1986 and 30.6.19, involved a total of 501 people. (1) Its best known form is that of food origin, to which are added the infantile and wounded ones. Attention should be paid to homemade preserves and honey for babies.
Contamination of food aside from Clostridium botulinum, agent of botulism, represents one of the most serious threats to food safety. botulinum is an anaerobic bacterium capable of producing extremely heat resistant spores and neurotropic toxins. Botulinum toxins are inactivated at a temperature of 80 ° C for at least 10 minutes, while for spores the inactivation temperatures are much higher, as we will see.
Among food poisoning, botulism is undoubtedly the most dangerous as neurotoxins are able to block the activity of motor neurons, resulting in flaccid paralysis of various muscle groups. Symptoms develop fairly quickly, as toxins are already present within the food product. They appear on average 12-36 hours after ingestion of the contaminated food and can rarely last up to 15 days. Paralysis has a downward trend, with initial involvement of the eye muscles and consequent visual disturbances (diplopia, or double vision, and blurred vision), followed by paralysis of the swallowing and speech muscles, incoordination of movements, paralysis of the upper limbs and lower. Depending on the dose of toxin ingested, clinical symptoms can range from very mild to very severe. They can also result in the death of the person (in about 5% of cases) - especially in patients not undergoing intensive care - due to paralysis of the diaphragm and respiratory muscles.
Food at risk
The spores of Clostridium botulinum they can contaminate a wide range of products. First of all the plants, since in contact with soil, soil and dust. The wide distribution of the spores means that they can be ingested by different animals and are thus found in the intestines of many mammals and fish, as well as in the seabed and lake. The plants are particularly exposed to contamination as, if soiled with soil and not carefully washed, the spores of botulinum they persist there for a long time.
Some homemade preserves - based on mushrooms, aubergines, olives, etc. - are particularly at risk. Insofar as they are not subjected, as is instead industrial practice - to temperatures that guarantee the destruction of the spores (121 ° C for at least 3 minutes). The subsequent addition of oil creates the anaerobiosis necessary for the development of the microorganism, which germinates from the spore and produces neurotoxins. Only conditions of high acidity (pH below 4,6) can hinder the development of clostridium and the production of botulinum toxins.
Botulinum, the name attributed to the bacterium, on closer inspection comes from the Latin botulus, that is, sausage. The first often fatal cases of botulinum intoxication were in fact reported following the consumption of pork sausages or blood sausages, where clostridium could develop. Since the spores can remain in the intestines of many mammals, slaughtering the pig can lead to contamination of the meat. And it is precisely to prevent the germination of spores - and the consequent development of Clostridium botulinum, with the production of neurotropic toxins - that some additives with a preservative function (nitrites and nitrates of sodium and potassium) are systematically added to various meat products (e.g. salami, cooked hams, mortadella, sausage, etc.). (2)
Infantile botulism and wound botulism
Infant botulism it is particularly insidious because it affects children under the age of 1 year, particularly between 3 and 6 months of age. It is often the cause of sudden cot deaths of babies just a few months old. Unlike alimentary botulism, the disease is not due to the ingestion of preformed botulinum toxins but to the ingestion of the spores alone. One of the most dangerous foods for infants is honey, sometimes rich in spores which - once ingested - germinate in the child's intestine and produce neurotoxins ,. In children older than one year - as well as in adults - the intestinal bacterial flora, on the other hand, prevents the development of vegetative forms, so that the spores that may be ingested do not cause damage.
Injury botulism it is instead caused by the penetration of spores (present in soil and dust) into fairly deep wounds, generally of the lacerated-bruised type, not properly disinfected. The bacteria that process neurotoxins originate from the germination of the spores, facilitated in their development by the lack of oxygen in the deep parts of the injured tissue. The incubation period can vary from 4 to 14 days and the symptoms are the same as in the food form. Cases of wound botulism have also been described in drug addicts (due to poor hygiene in the use of syringes).
Silvia Bonardi and Dario Dongo
(1) National Institute of Health, ISS. (2010). Focus on food botulism, https://www.iss.it/focus/-/asset_publisher/92GBB5m5b1hB/content/id/4542962
(2) Research and development, in recent years, have been oriented towards the possible use of vegetable ingredients with preservative functions. See previous articles
- natural preservatives in meat, https://www.greatitalianfoodtrade.it/etichette/conservanti-naturali-nelle-carni,
- plant extracts with preservative functions, short circuit in Europe, https://www.greatitalianfoodtrade.it/consum-attori/estratti-vegetali-nelle-carni-cortocircuito-in-europa,
- natural preservatives in meat, prickly pear. V. https://www.greatitalianfoodtrade.it/tecnologia-alimentare/conservanti-naturali-nelle-carni-il-fico-d-india-studio-università-di-catania