What causes food poisoning and how can we avoid it?

We have all been there – gripping onto the toilet seat, beads of sweat forming, mouth like an emery board as you wonder exactly which tub of leftovers in your fridge is to blame for it all going wrong.

According to the New South Wales Food Authority, an estimated 4.1 million Australians are affected by food poisoning each year. Symptoms are all nefariously memorable, from vomiting, nausea, diarrhoea and stomach cramps, to fever that, on rare occasions, can be fatal.

One particular type of food poisoning that has caused some panic online is the illness caused by Bacillus cereus or B. cereus. Better known by its online alias, ‘fried rice syndrome.’

Although you can’t see it, B. cereus is a bacterium that is virtually impossible to avoid in our day-to-day lives. Its spores lie dormant in places including our soil, water and you guessed it, our food.

Professor Si Ming Man is an immunologist at the John Curtin School of Medical Research at The Australian National University (ANU). Man compares the bacteria’s spores to “zombies” that – similarly to the fictional kind – can be very hard to kill.

“Under conditions where nutrients are scarce, the bacterium turns into a spore or ‘zombie’ and remains dormant,” says Man.

“Just like most bacteria or microbes, B. cereus and their spores can be transferred easily from touching contaminated soil or surfaces, ending up on our hands or edible items such as veggies, and then onto our food.

“Spores are also very hardy and can survive heat during the cooking process. They can be resurrected in warm and nutrient-rich environments like cooked rice and germinate into active bacteria and produce toxins.

“These can survive for years and even centuries.”

Given its nickname, it’s no surprise that ‘fried rice syndrome’ is typically caused by consuming starchy foods. Unfortunately fresh foods can also be a breeding ground for B. cereus’ toxic spores.

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“B. cereus can grow in fresh pasta, potatoes, dairy products, meat, unwashed fruits and vegetables.

“An interesting scientific study showed that B. cereus is found in 41 per cent of cereal products including rice and other starchy foods, in 45 per cent of bean products, 37 per cent of vegetables, and in 36 per cent of dairy products.”

Because B. cereus can survive the reheating process, it’s best to let foods such as cooked grains cool down before chilling and only reheat cooked rice once before binning it.

But even with these precautionary measures, your risk of food poisoning isn’t eliminated altogether.

ANU PhD scholar Radhwan Al-Zidan says B. cereus is just one of at least 30 different types of bacteria that can upset your stomach and ruin your day.

“Many everyday foods can harbour bacteria that cause food poisoning. For example, doughnuts. Three years ago in Canberra, a contaminated batch of doughnuts led to over 200 cases of gastro.

“Another incident involved potato salads containing a raw egg-based mayonnaise contaminated with salmonella made more than 140 people sick.”

In most cases, devilish doughnuts and malaise-causing mayonnaise are purged from one’s system after 24 to 48 hours—but for vulnerable individuals, side effects can be more severe.

“The time it takes for symptoms to show up depends on the type of microbes. It can range from a few hours -B. cereus – to a few days – E. coli,” says Al-Zidan.

“Young children, pregnant women, elderly people -above 65 years old – and those with a weakened immune system are more likely to get food poisoning and have worse symptoms.”

If this knowledge isn’t enough of an incentive to chuck out the slowly forming science experiment in your fridge, the researchers leaves us with one sensible piece of advice.

“If you think your food carries any bacterial contamination, we strongly recommend throwing them away,” warns Man.

“Eating contaminated food can cause food poisoning, and in people with a weakened immune system, it could lead to sepsis and even death.”