BBC Science Focus

…I GET FOOD POISONING?

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Most of us are all too familiar with the unpleasant symptoms of food poisoning, from vomiting to diarrhoea and debilitati­ng stomach cramps. Although viruses play a role, bacteria are common offenders, with Salmonella and Campylobac­ter topping the poisoning charts. Some bacteria wreak havoc by multiplyin­g in the body before delivering their toxins, which spark an immune reaction in the gut. Others, such as

Staphyloco­ccus aureus, poison us by contaminat­ing food with toxins. 1. Bacteria enter

Some bacteria or enterotoxi­ns (intestinal toxins) can survive harsh stomach conditions, making their way to the gut. There, the misery begins, sometimes up to 72 hours after eating the offending meal.

2. Bacteria multiply

Undetected by the body’s immune system, the bacteria quietly multiply, producing toxins. These invade and penetrate the gut lining, setting off a strong immune response.

3. Immune response

Immune cells release signalling proteins called pro-inflammato­ry cytokines, which set in motion a series of steps causing gut inflammati­on and swelling, leading to discomfort.

4. Flooded intestines

The intestinal wall is designed to absorb nutrients and water from food. Bacterial toxins can cause pores to open in the wall, allowing water and other molecules to flood in.

5. Diarrhoea and dehydratio­n

The excess fluid and electrolyt­es in the gut lead to watery diarrhoea, which has a beneficial role of flushing out the bacteria and their toxins. It can, however, cause dehydratio­n.

6. Vomiting

Some bacteria don’t cause vomiting, but Staphylo

coccus aureus enterotoxi­ns do. Research suggests that they may stimulate the vagus nerve which transmits a signal to the brain’s vomiting centre.

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