Clostridium perfringens food poisoning

Clostridium perfringens produces spores with a protective coat, which means they can survive normal cooking. After a dish has been cooked, the spores germinate if the food stays warm for long enough, and the bacteria multiply rapidly. When contaminated food is eaten, the bacteria produce a toxin in the intestine that causes illness.

The US Centers for Disease Control and Prevention links outbreaks mainly with poultry, beef, pork and gravy prepared in large batches and held at unsafe temperatures. This is why the illness is so closely associated with catering rather than with home cooking of single portions.

The characteristic picture is watery diarrhoea with stomach cramps. Vomiting and fever are not usually prominent, which helps to distinguish it from several other food-borne infections. The NHS describes food poisoning in general as causing feeling or being sick, diarrhoea, tummy pain, a high temperature and feeling generally unwell, symptoms that usually settle within a week.

Because many people eat the same dish, illness often affects a cluster of diners who became unwell at around the same time, which is a clue to environmental health officers investigating an outbreak.

Healthy adults tend to recover without treatment. The NHS identifies infants, older adults and people with weakened immunity as higher-risk groups for food poisoning generally. Outbreaks of this particular organism occur predominantly in institutions such as hospitals, school canteens, prisons, nursing homes and large events, where food is cooked in bulk and may be kept warm for a long time before serving. The CDC notes that outbreaks peak in the cooler months around holiday meals.

The NHS advises resting, taking small and frequent sips of fluid to avoid dehydration, continuing to feed babies as usual, and using paracetamol for discomfort. Fruit juice, fizzy drinks and anti-diarrhoea medicines are not recommended for children under 12. Pharmacists can supply oral rehydration sachets and, for adults, loperamide.

• Drink little and often rather than large amounts at once.

• Eat bland food when you feel able.

• Stay at home and wash hands thoroughly to avoid spreading illness; the NHS suggests staying off for at least two days after symptoms stop for diarrhoea and vomiting bugs.

• Do not prepare food for others while unwell.

NHS 111 can advise if there are signs of dehydration, persistent vomiting, blood in the stool, diarrhoea lasting more than seven days or vomiting more than two days. Call 999 or go to A&E for vomiting blood, a severe headache with a stiff neck, severe abdominal pain, difficulty breathing or confusion. Diagnosis is usually clinical, but stool tests can be sent in an outbreak so that the cause can be confirmed.

Because spores survive cooking, prevention depends on controlling temperature afterwards. The CDC emphasises keeping food at safe temperatures. Practical steps include cooling large joints and pots quickly by dividing them into shallow containers, storing leftovers in the fridge soon after the meal, reheating until steaming hot throughout, and serving hot dishes straight away rather than leaving them on a counter.

The World Health Organization encourages the Five Keys to Safer Food: keep clean, separate raw and cooked, cook thoroughly, keep food at safe temperatures and use safe water and raw materials.