Food Poisoning Bacteria: Types, Symptoms and Prevention

The main food poisoning bacteria in UK catering are Campylobacter, Salmonella, Shiga toxin-producing E. coli, Listeria monocytogenes and Clostridium perfringens. They spread through contaminated food, poor temperature control and cross-contamination. Prevent them through thorough cooking, rapid chilling, clean handling, strict separation and effective food safety management.

Last updated: June 2026
Author: Global Safety Academy Editorial Team
Technically reviewed by: Global Safety Academy Food Safety Quality Review Team

Professional limitation: This article provides general food-safety information, not medical or legal advice. Anyone with severe, persistent or concerning symptoms should seek appropriate medical advice. Food businesses must apply controls appropriate to their products, processes and jurisdiction.

Key facts

• Campylobacter remains the most frequently reported cause of bacterial gastroenteritis in England.

• Bacteria do not all behave in the same way; some form spores, produce toxins or grow under refrigeration.

• Raw poultry, eggs, minced meat and chilled ready-to-eat foods require particular care.

• Food may look, smell and taste normal while containing harmful bacteria.

• Cooking, chilling, cleaning and preventing cross-contamination are essential controls.

• Slow cooling and inadequate hot holding can allow surviving bacteria to multiply.

• Children, older adults, pregnant women and immunocompromised people may experience more serious illness.

How Food Poisoning Bacteria Cause Illness

Key takeaway: Food poisoning develops when harmful bacteria, bacterial toxins or large numbers of bacterial cells enter the body through contaminated food.

Food poisoning bacteria can contaminate food at any stage from farming and processing to delivery, preparation, storage and service. Contamination may originate from animals, soil, water, raw ingredients, food handlers, equipment or other foods.

Some bacteria cause infection by entering and multiplying in the body. Others cause illness through toxins. Symptoms vary according to the organism, the amount consumed, the food involved and the person’s health.

Typical symptoms can include:

• Diarrhoea

• Stomach cramps

• Nausea

• Vomiting

• Fever

• Headache

• Dehydration

Certain infections can also cause bloody diarrhoea, kidney complications, bloodstream infection, meningitis, pregnancy complications or long-term health effects. UKHSA advises that young children, older adults and people with weakened immune systems are at greater risk of serious gastrointestinal illness.

What bacteria need to multiply

Bacterial growth depends on several interacting conditions:

• Food: Many bacteria grow well in protein-rich, moist foods.

• Moisture: Bacteria generally require available water.

• Warmth: Inadequately chilled or hot-held food may support rapid growth.

• Time: Even a small contamination can become significant if food remains under favourable conditions.

• Acidity: Many bacteria grow poorly in highly acidic foods, although tolerance varies.

• Oxygen: Some need oxygen, while others grow with little or no oxygen.

These factors are not identical for every organism. Listeria can multiply at refrigeration temperatures, while spore-forming bacteria such as Clostridium perfringens may survive cooking and grow during slow cooling or warm storage.

Regulation (EC) No 852/2004 requires food businesses to protect food from contamination and maintain appropriate temperature-controlled handling and storage conditions.

The Main Food Poisoning Bacteria in UK Catering

Key takeaway: Campylobacter causes the largest number of reported bacterial gastrointestinal infections, while Salmonella, STEC and Listeria remain important because of their frequency or potential severity.

UKHSA recorded 69,394 Campylobacter laboratory reports in England in 2025, compared with 10,406 reported Salmonella cases. There were also 181 confirmed listeriosis cases in England and Wales during 2025. These surveillance figures are laboratory reports, not estimates of every foodborne case occurring in the community.

The onset periods are guides rather than a reliable way to identify which meal caused illness. A person may associate symptoms with the most recent food they ate even when the responsible exposure occurred several days earlier.

Campylobacter

Campylobacter is the most common reported bacterial cause of gastroenteritis in England. Poultry is an important source, and contamination can spread from raw chicken to salads, utensils, hands and food-contact surfaces.

It does not normally need to multiply in food to create a risk. A small transfer from raw poultry to ready-to-eat food may be enough to cause illness.

Key controls include:

• Cooking poultry thoroughly

• Avoiding washing raw chicken

• Separating raw poultry from ready-to-eat food

• Cleaning and disinfecting contaminated surfaces

• Washing hands after raw-food handling

• Cooking chicken liver dishes thoroughly

Salmonella

Salmonella is associated with poultry, meat, eggs, raw produce and unpasteurised products. UKHSA reported 10,406 Salmonella cases in England in 2025, the highest annual figure in a decade, although only slightly above the 2024 total.

Symptoms usually begin within 12–96 hours and may include diarrhoea, abdominal pain, nausea, vomiting and fever. Illness may be more serious in young children, older adults, pregnant women and immunocompromised people.

Shiga Toxin-Producing E. coli

Shiga toxin-producing Escherichia coli, or STEC, includes E. coli O157 and other toxin-producing strains. Cattle are an important reservoir, and infection may follow consumption of undercooked minced beef, unpasteurised milk, contaminated produce or water.

Very few STEC cells may be sufficient to cause infection. Some people develop haemolytic uraemic syndrome, a serious complication that can cause kidney failure and particularly affects children.

Whole cuts of meat and minced meat require different controls. Bacteria on a whole cut are mainly expected on the exterior, while mincing can distribute surface contamination throughout a burger or meat product.

Listeria monocytogenes

Listeria is less common than Campylobacter or Salmonella but can cause severe illness in pregnant women, unborn babies, newborns, older adults and immunocompromised people.

Unlike many other food poisoning bacteria, Listeria can grow at refrigeration temperatures. It is particularly associated with chilled ready-to-eat products that receive no further cooking and may have extended shelf lives.

In 2025, 181 listeriosis cases were reported in England and Wales. Pregnancy-associated infections represented around one fifth of reported cases, while incidence was highest among people aged 80 and over.

Clostridium perfringens

Clostridium perfringens is a spore-forming bacterium commonly associated with large-scale catering, bulk cooking and food kept warm for extended periods.

Its spores may survive cooking. If a large pot of meat, stew, gravy or sauce cools slowly, the spores can germinate and the growing cells can multiply rapidly. Outbreaks are therefore often linked to food prepared in advance, cooled inadequately or held at unsafe temperatures.

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High-Risk Foods and People More Vulnerable to Illness

Key takeaway: High-risk foods support bacterial survival or growth and are often eaten without a further cooking stage capable of removing the hazard.

A high-risk food is not necessarily unsafe. It requires stronger controls because its composition, handling or intended use makes bacterial contamination more consequential.

Examples include:

• Cooked meat and poultry

• Gravies, stocks, soups and sauces

• Cooked rice and pasta

• Eggs and egg-based dishes

• Dairy products

• Seafood and smoked fish

• Soft and mould-ripened cheeses

• Sandwich fillings

• Prepared salads

• Pâté

• Sliced cooked meats

• Chilled ready-to-eat meals

• Foods containing fresh cream

Raw poultry, minced meat and unpasteurised products also require careful control because they may carry harmful bacteria before cooking.

Food may remain unsafe even when it looks and smells normal. The FSA advises that harmful bacteria cannot necessarily be detected through sight, smell or taste.

People at increased risk

Food poisoning can affect anyone, but the consequences may be more severe for:

• Babies and young children

• Pregnant women and unborn babies

• Older adults

• People receiving immunosuppressive treatment

• People with weakened immune systems

• People with certain underlying medical conditions

Extra care is required in hospitals, care homes, nurseries and other settings serving vulnerable groups. Listeria controls are especially important where chilled ready-to-eat food is supplied to pregnant, older or immunocompromised consumers.

Spores and Toxins: Why Reheating Is Not Always Enough

Key takeaway: Cooking and reheating can destroy many bacterial cells, but they cannot correct every failure involving spores, toxins, slow cooling or repeated contamination.

Normal cooking temperatures effectively destroy organisms such as Campylobacter and Salmonella when the required time and core temperature are achieved. Some bacteria, however, survive adverse conditions by producing spores.

Clostridium perfringens spores may survive cooking and later germinate if food cools too slowly or remains warm for too long. The risk is controlled by dividing large batches, cooling promptly, refrigerating correctly and reheating only through an approved process.

Other spore-forming bacteria can create heat-stable toxins. For example, the FSA states that cereulide produced by some strains of Bacillus cereus is unlikely to be destroyed by cooking or boiling. This demonstrates why a later reheat cannot be treated as a universal rescue step for food that has already been stored unsafely.

Worked example: cooling a large pot of gravy

A catering team prepares a deep stockpot of gravy for service the following day. The pot is left covered at room temperature for several hours before being placed in a refrigerator.

The outside may cool while the centre stays warm enough for spore-forming bacteria to grow. Placing the entire hot pot in a refrigerator may also warm surrounding food and overload the appliance.

A safer process is to:

1. Divide the gravy into smaller, shallow containers.

2. Protect it from contamination during cooling.

3. Use a blast chiller or another validated rapid-cooling method.

4. Check the cooling process with a clean probe.

5. Refrigerate promptly.

6. Record corrective action when the cooling limit is missed.
   

Preventing Food Poisoning Through the 4 Cs

Key takeaway: Cooking, chilling, cleaning and preventing cross-contamination control the main ways bacteria survive, multiply and spread in catering.

Cooking

Cooking must achieve a safe time-and-temperature combination throughout the food. Particular attention is required for poultry, minced meat, rolled joints, liver dishes and reheated food.

A common catering control is a core temperature of 75°C for 30 seconds or a validated equivalent. Detailed limits are covered in the food safety temperatures guide.

Chilling

Cold storage slows bacterial growth but does not make food sterile. Chilled food should be moved into refrigeration promptly, stored within the business’s temperature limits and used within its safe shelf life.

Large batches should be divided into smaller portions before chilling. Fridges must not be overloaded, and hot food should not compromise the temperature of other chilled products.

Cleaning

Food-contact equipment must be cleaned and, where required, disinfected effectively. Staff must follow the product’s dilution, application and contact-time instructions.

Cleaning should include:

• Preparation surfaces

• Chopping boards

• Knives and utensils

• Slicers and mixers

• Refrigerator handles

• Taps

• Cloths and cleaning equipment

• Food-probe thermometers

Cross-contamination control

Raw food must be kept away from cooked and ready-to-eat food. Use separate equipment, protected storage and effective handwashing between tasks.

The full separation process is explained in preventing cross-contamination in the kitchen.

Personal hygiene

Food handlers must report illness, wash their hands at critical moments, wear clean protective clothing and protect wounds appropriately.

The FSA’s fitness-to-work guidance generally requires staff with diarrhoea or vomiting to remain away from open-food work until symptom-free for at least 48 hours. See personal hygiene for food handlers.

Daily bacterial-control checklist

• Approved suppliers and deliveries are checked.

• Raw and ready-to-eat food are separated.

• Chilled and frozen storage is monitored.

• Cooking limits are checked with a clean probe.

• Hot food is held at the required temperature.

• Cooling processes are controlled and recorded.

• Cleaning and disinfection schedules are completed.

• Food handlers report illness immediately.

• Use-by dates and stock rotation are checked.

• Unsafe food is isolated or discarded.

• Managers investigate repeated control failures.

Build Practical Food-Safety Competence

Key takeaway: Effective training helps food handlers recognise bacterial hazards and apply prevention controls during real catering operations.

Food poisoning prevention depends on more than memorising bacterial names. Staff must understand how their own actions affect cooking, cooling, storage, cleaning and cross-contamination.

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Sources and Methodology

Key takeaway: This article uses current UK surveillance evidence, primary food-hygiene legislation and official food-safety guidance.

The article was checked against official sources available in June 2026:

• Food Standards Agency

• UK Health Security Agency

• UKHSA gastrointestinal infection data

• Regulation (EC) No 852/2004

• FSA Safer Food, Better Business

• Food Safety Act 1990

Surveillance figures describe reported or laboratory-confirmed cases and should not be presented as the total number of infections caused specifically by food.