Clostridium botulinum

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Causes botulism food poisoning – which is rare, but deadly if not treated. The toxin it produces (also sold as Botox®) is one of the most potent nerve toxins ever studied

C. botulinum grows well in places with low oxygen, such as cans of food that became contaminated before being sealed. Minute amounts of toxin can cause paralysis and suffocation. With antitoxin and a ventilator the paralysis usually goes away within weeks – or in severe cases, months. Wound botulism is far more common – principally in IV drug users. Clostridium botulinum is one of the most important pathogens associated with food. The organism forms spores that are resistant to many common food process controls. Botulinum neurotoxins (BoNT) produced by vegetative cells of this Gram positive, anaerobic bacterium are among the most potent biological neurotoxins known. The toxin does have clinical applications (in tiny concentrations!) but there are some who inject into their faces – it’s marketed as Botox®. Foodborne botulism is a very severe intoxication, historically caused by eating preserved low acid, low oxygen foods (e.g. canned vegetables, meat and fish) in which C. botulinum had grown and produced toxin. Symptoms appear between 12 and 36 hours after consuming the contaminated food with nausea, vomiting and diarrhoea followed by paralysis of the eyes, mouth, throat and – progressively – muscles. Children under 1 year old should never be fed honey which has been linked to infant botulism (but not to adult botulism) – it is a reservoir for botulism spores. Constipation is often the first sign then a dull face, weak sucking, weak cry, less movement, trouble swallowing, more drooling than usual, muscle weakness and breathing problems. Infant botulism is an extremely rare toxic infection that occurs when C. botulinum grows and produces toxins in the intestines of babies; symptoms appear after 3-30 days and include constipation, lethargy, floppiness and breathing difficulties. This is why babies under a year old must not be fed honey. Not all C. botulinum cause illness in humans and wound botulism is far more common than foodborne intoxication – but as most food businesses don’t sell black tar smack as a rule we’ll stick to the foodborne disease in the tabs below.

Growth and Control Toxins Clinical Notes
Normally grows in the absence of oxygen. Outbreaks have been implicated in low acid canned foods such as garlic and oil preparations. In addition, outbreaks have been caused by foil wrapped baked potatoes improperly cooled and then used to make potato salads. Those canning their own foods need to take special care with those that are low in acid. Botulism is prevented in commercially-canned food by cooking at 121°C (250°F) for 3 minutes thus killing the spores. While botulism poisoning is very rare, the organism is common in the soil and can survive in the environment as a resistant spore which stays dormant until exposed to conditions that support growth. Like the other clostridia C. botulinum forms a spore which makes proper cooling and reheating very important.
C. botulinum produces a potentially fatal toxin. This toxin is reasonably heat-stable but is destroyed by heating at >80°C. While the toxin has legitimate medical uses is one of the most potent nerve toxins ever discovered yet is injected into the faces of the vain under the trade name Botox®. The medical term for such people is ‘morons’. Strains produce one of seven known types of BoNT (A to G). Only those producing types A, B, E and F cause botulism in humans. Strains are also separated into two groups based on physiological differences:
Group I (can produce A, B or F toxin) are proteolytic (break down protein) and cause food spoilage
Group II (can produce B, E or F toxin) are non-proteolytic and may be present in foods without obvious spoilage
Foodborne and infant botulism is caused by C. botulinum in Groups I and II; more common is wound botulism in IV drug users
Don’t forget to read the disclaimer! There are three main types of botulism – foodborne botulism, intestinal botulism (due to proliferation of the organism in the gut) and wound botulism. Wound botulism in intravenous drug users is the most common presentation. The most common food-related outbreaks of botulism are linked to incautious home preserving of foodstuffs but – rarely – other canned foods can be tainted with the bacteria. Symptoms often begin with blurred vision and difficulty in swallowing and speaking, but diarrhoea and vomiting can also occur. Symptoms of food borne botulism usually turn up 18 to 36 hours after eating tainted food, but it can take up to 10 days for symptoms to occur. The disease can progress to paralysis. Most cases will recover, but the recovery period can be many months. The disease is fatal in 5-10% of cases; death is due to respiratory failure. When caught early an anti-toxin is available to stop the spread of the bacteria and emetics are often used in an attempt to rid the body of tainted food particles. Honey is the only known dietary reservoir of botulinum spores. This is the reason honey is not recommended for infants under 12 months. The Clostridium botulinum organism is killed by quat-based sanitisers – any Chemex product carrying the ‘Bio-Tested’ mark. The spores are killed by heating or by oxidisers such as  Antibak.

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