Garlic kills food bacteria

Alexandre Dumas, author of ‘The Three Musketeers’, described the air of the French region of Provence as being “particularly perfumed by the refined essence” of garlic. Old Alexandre may have been a touch optimistic in his use of the term “perfumed” but his attitude reflects the high regard that this herb has been held in for centuries, and now a new study has shown that garlic is indeed even more potent as a medicine than some modern pharmaceuticals.

The first ever garlic prescription that we have evidence of was written on a clay tablet and comes from the Sumerian civilisation in about 3000 BCE. Garlic was popular among many ancient civilisations from Europe to China although the pungent smell of garlic offended the Greeks and they did not allow people who ate it to enter some temples. Even the Greeks though recognised that garlic had singular powers. Greek athletes ate garlic before competition and Greek soldiers chewed it before battle.

Across many cultures there was an upper class dislike for garlic that arose mainly from the view that its smell indicated that it was ‘vulgar’ or common. The peasantry however, loved it and viewed it as a cure-all. Reports from England of the 16th century show that the peasants not only used it for themselves but also on their livestock to make them stronger. In the Elizabethan era the Latin word for antidote, ‘theriaca’, had become the English word ‘treacle’ meaning a cure-all. Garlic was known as this time as ‘poor man’s treacle’. Over the centuries though the upper class resistance to using garlic dropped, mostly out of necessity, and by World War I British, French and Russian medical officers were using Garlic to treat infected battle wounds. It is this antibacterial action of garlic that has been resoundingly proven in a new study.

The new research focused on a bacterium called Campylobacter which is the most common bacterial cause of food-related illness. Symptoms of Campylobacter infection include diarrhoea, stomach cramping, abdominal pain, and fever. These bacteria are also responsible for causing 33 per cent of all known cases of a paralysing disorder known as Guillain-Barre syndrome.

Diallyl sulphide is a compound from garlic that has known antibacterial action and these researchers wanted to see how this compound might act against Campylobacter once it has formed a protective biofilm.

A biofilm is a collection of bacteria in which the organisms adhere to each other on a surface. These bacteria are embedded within a self-produced combination of DNA, proteins, and polysaccharides that acts like a polymer and which we call slime. Bacteria living in a biofilm have significantly different properties to bacteria living alone and they are more resistant to antibiotics (yet another argument for the joys of community living). Biofilms can grow in showers, in pipes, and on floors and bench surfaces that are not properly cleaned. They can also grow on food and in some cases antibiotics can become ineffective against them.

When the researchers tested a Campylobacter biofilm they found that it was 1000 times more resistant to antibiotics than free floating bacterial cells. Diallyl sulphide however, was able to penetrate the biofilm and combine with a sulphur containing enzyme in the bacteria, changing the enzyme’s function, and shutting down the bacteria’s metabolism.

The diallyl sulphide was found to be 100 times as effective as the antibiotics erythromycin and ciprofloxacin and also worked much faster.

This does not prove that garlic will prevent Campylobacter poisoning but it does show that diallyl sulphide will. The researchers says that it could be used both to deal with the bacteria in the environment as well as in cleaning industrial food processing equipment. In the meantime adding garlic to your food has a definite hygiene as well as taste function. If you want to go a step further, why not rub down those kitchen surfaces with a few bulbs of garlic? Your kitchen might have a slightly pungent scent to it, but just making breakfast every day will certainly clear the sinuses.