In this chapter

This chapter introduces the main microbiological entities behind most food poisoning outbreaks in the UK, and explains the difference between food poisoning and food borne disease.

Definition of food poisoning

Food poisoning is caused by eating sufficiently large numbers of pathogenic bacteria that are living on or in the food. It takes many hundreds of thousands of bacteria to make you ill, however a square millimetre can contain sufficient numbers to cause illness.

Food poisoning is defined as ‘an acute illness of sudden onset caused by the consumption of food containing poisonous micro-organisms (bacteria)’.

Types of Food Poisoning:

Pathogenic Bacteria:

The most common cause of food poisoning illness. It is caused by eating infected food which makes a person feel unwell. Examples of pathogenic bacteria which can cause food poisoning are Salmonella, Clostridium perfringens, Staphylococcus aureus, Bacillus cereus.

Foodborne Disease:

Foodborne diseases represent the greatest danger to humans and should not be confused with ordinary food poisoning bacteria. Foodborne diseases are potential killers, passed to humans by bacteria carried on contaminated food or in contaminated water.

Importantly, the food or water is only the method of transportation, foodborne disease does not need the food to grow or multiply, and it only takes a few bacteria can make you seriously ill.

Examples of foodborne disease include:

• Campylobacter Enteritis
• Escherichia coli 0157, (E.Coli 0157)
• Typhoid
• Dysentery
• Hepatitis
• Tuberculosis (TB) - (Untreated Milk)

The incubation period can be days, weeks or months. The illness can last for one or two days, or continue for years as the infection can invade the bloodstream, and induce long-term health problems.

Other symptoms can be kidney failure or paralysis, which can lead to death. Symptoms of foodborne disease are sometimes similar to bacterial food poisoning.

Food Poisoning Viruses

Passed from person to person through contact and bodily fluids. Examples include Norovirus and Hepatitis A.

Other causes of food poisoning include:

• Viruses living on and in people and animals
• Moulds usually seen as spoilage on products such as bread
• Chemicals such as cleaning chemicals and pesticides
• Metals absorbed into food from unsuitable metal containers or pipes
• Organic materials such as under-cooked red kidney beans and rhubarb leaves can be fatal along with some fungi (mushrooms) and fish such as the Fugu or Japanese pufferfish which can kill you if not prepared correctly. Take no risks: if in doubt, check and double check with your Supervisor or EHO.

The main culprits of food poisoning in the UK are:

• Campylobacter: The UK’s most common cause of food poisoning. These bacteria are usually found on raw or undercooked meat (particularly poultry), also known as ‘The BBQ Bug’, on unpasteurised milk and untreated water.
• Salmonella: bacteria are often found in raw or undercooked meat, raw eggs, milk, and other dairy products.
• Listeria: bacteria may be found in a range of chilled ‘ready-to-eat’ foods, including pre-packed sandwiches, cooked sliced meats, pâtés and soft cheeses (such as Brie or Camembert which are unpasteurised). All of these foods should be eaten by their use-by dates. This is particularly important for pregnant women, because a listeria infection (known as listeriosis) in pregnancy can cause pregnancy and birth complications and can result in miscarriage.
• Escherichia coli (E. coli): bacteria found in the digestive systems of many animals, including humans and whilst most strains are harmless some can cause serious illness. Most cases of E. coli food poisoning are caused by eating undercooked beef (particularly mince, burgers and meatballs) or drinking unpasteurised milk.

Top 10 Causes of food poisoning

1. Preparing food too far in advance and storing at room temperature (time in Danger Zone)
2. Cooling food too slowly, before being refrigerated / frozen / served (time in Danger Zone)
3. Not reheating food to sufficient temperature to kill bacteria (82°C for 2 minutes)
4. Using cooked food that has already been contaminated with food poisoning bacteria
5. Undercooking food, (food cooked below 75°C and / or less than 2 minutes)
6. Not thawing frozen food properly
7. Cross contamination from raw food to high risk foods
8. Eating contaminated uncooked raw foods such as eggs, fish & shellfish
9. Not storing hot food correctly (hot-holding at or below 63°c)
10. Food Handlers infected or using poor hygiene standards

How do bacteria multiply?

Bacterial food poisoning occurs if food is eaten after it has been contaminated by pathogenic bacteria in sufficient numbers.

Bacteria reproduce by continually dividing in a process called Binary fission. This is where one bacteria splits and becomes two (which in turn splits into four, then four split into eight and so on). Bacteria only need 10 - 20 minutes to multiply so can multiply to dangerous levels in a short space of time.

Spores

Some bacteria have evolved the ability to survive very high cooking temperatures and other harsh conditions including dehydration or disinfection. They do this by forming a spore, a protective coating or shell around themselves.

Bacteria do not multiply when they are in spore form, but as soon as conditions improve for them (back in the danger zone) the bacteria emerge from their spores and resume multiplication.

The best defence against spores is to reduce the time taken to get the food from preparation to service. Bacteria often found in rice is particularly effective at forming spore resistance and will not be killed by reheating, so our advice is to never store and reheat cooked rice. If you do keep cooked rice, it is now a legal requirement to keep it refrigerated and it is must be used within 24 hours.

Toxins

Toxins can be formed when the bacteria is destroyed. Like spores, toxins are a defence method. Once you kill the bacteria, it releases a toxin, (poison), from its cell wall.  Toxins can be resistant to heat and may require cooking at high temperatures for a long time.

The best defence against toxin forming bacteria is:

• Always use a reputable food supplier
• Prepare, cook and serve quickly to reduce the time bacteria has to multiply
• Ensure food handlers have good personal hygiene
• Follow the key points covered in this course!

What are my responsibilities as a Food Handler?

Every food handler has a responsibility to help safeguard the health of their customers. Food handlers have a legal obligation to produce and keep food safe to eat. This means everyone - no exceptions.

Chapter summary

By the end of this chapter you should have developed the following understanding and insights:

• An awareness  of microbiological threats including pathogenic bacteria, viruses, and moulds
• An understanding a range of common practical failures that result in food poisoning
• An awareness of bacterial spores and toxins and their effect on the body
• An awareness of the differences between a food poisoning and food borne disease