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Explainer: the good, the bad and the ugly of botulinum toxin

It might be fine for us to inject ourselves with Botox in a quest for eternal youth, but when the microorganism that produces this potent toxin is found in whey powder that might end up in baby milk formula…

Magnification (1,000 times) of Clostridium botulinum from food, which causes a severe form of food poisoning called botulism. Microbe World/Flickr

It might be fine for us to inject ourselves with Botox in a quest for eternal youth, but when the microorganism that produces this potent toxin is found in whey powder that might end up in baby milk formula, there’s reason for great concern.

This is exactly what’s happening in a number of countries right now, after representatives of the New Zealand dairy company Fonterra said on Saturday that a batch of whey powder produced last year could contain the bacteria. The powder was exported to Australia, China, Saudi Arabia, Vietnam, Thailand and Malaysia.

Vietnam, Russia and China have banned imports of both whey powder and infant formula from New Zealand although no cases of infection have been reported so far.

The organism at the centre of the controversy is Clostridium botulinum, a food-borne pathogen that causes a severe form of food poisoning called botulism. Botulism is caused by the production of botulinum toxin, the most potent neurotoxin known to man.

The toxin is at least a 10,000 times more potent than sarin, the nerve gas used by the Japanese doomsday cult in the 1995 Tokyo subway attack, which killed 13 people, severely injured 50 others, and caused harm to thousands of others.

What happens

Botulinum toxin causes flaccid paralysis (the inability of muscles to contract) by preventing the secretion of the chemical messenger acetylcholine, which tells muscles to contract; hence Botox’s power to deliver a smooth and wrinkle-free face.

Botulinum toxin paralyses muscles, hence Botox’s power to deliver a smooth and wrinkle-free face. Bella Medspa/Flickr

At first, an infected person may experience difficulties in focusing and swallowing. Progressive muscle paralysis develops and finally causes respiratory paralysis, which leads to death.

There’s an antitoxin for neutralising the botulinum toxin. But someone suffering from botulism might also need supportive measures, such as mechanical ventilation to help them breathe.

Up to 65% of people with botulism die if they are not treated immediately and properly. Even with treatment, recovery takes weeks and most people never recover fully. Long-term effects include fatigue, weakness, dizziness, shortness of breath and difficulty performing strenuous tasks.

Types of infection

Botulism is usually associated with improper food handling, especially in the preparation of home-tinned foods of low-acidity, such as green beans and mushrooms.

The toxin is so potent that the amount found in one bean from a contaminated can would be enough to kill an entire family. Thankfully, modern methods of food sterilisation and preservation, as well as tight control measures mean that classic food-borne botulism is very rare nowadays.

Wound botulism is another rare form of the illness where C. botulinum causes an infection through the use of contaminated needles in intravenous drug use.

But the most common form of this kind of poisoning these days is infant botulism (one of the causes of floppy baby syndrome).

As babies don’t have a fully developed gut microbiome, C. botulinum can easily colonise their large intestine; there aren’t enough “good bacteria” around to out-compete such pathogens.

The toxin is so potent that the amount found in one bean from a contaminated can would be enough to kill an entire family. Steve Hankins

Once it’s settled in, C. botulinum excretes botulinum toxin that’s slowly absorbed. Early signs of infection include constipation, feeding problems, lethargy and poor muscle tone, followed by full muscle paralysis.

Thanks to proper treatment and early diagnoses, infant and wound botulism currently have case fatality rates of approximately 15% and 1%, respectively.

Origins and uses

C. botulinum is commonly found in soil. To enhance its survival, it forms dormant cells known as endospores.

These spores are extremely resistant to a range of environmental pressures, and can survive boiling as well as resist chemicals used to kill bacteria. So, even if the bacteria are killed by normal heating of food, the spores will survive and start to germinate.

The spores can also be ingested through contaminated food and then grow to produce the deadly botulinum toxin. For this reason, raw honey, which is a known source of C. botulinum spores, isn’t recommended for babies less than a year old.

Botulinum toxin is not only used in the cosmetic industry; it has many medical uses from the treatment of severe muscle spasms to preventing excessive under-arm sweating.

But the susceptibility of infants, especially, to botulinum poisoning and the ability of C. botulinum to form heat-resistant spores means that contaminated food sources pose a great risk to humans.

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