Foodborne pathogens


Foodborne illness causes about 43,000 infections in Scotland each year, with around 500 people having to go to hospital. Some people are more vulnerable to infection: the elderly, people with weakened immune systems, pregnant women and young children. Food may not look, smell or taste any different if it contains these microbes.

Foodborne bacteria

Campylobacter jejuni microcolony on ileal tissue. Dr. Paul Everest, University of Glasgow. Microbiology (2010).

Many different types of bacteria can cause foodborne disease. Currently, the most important foodborne bacteria in Scotland are Campylobacter, Salmonella, Listeria monocytogenes and Shiga toxin-producing Escherichia coli. Symptoms usually begin one or two days after becoming infected, though they may appear as quickly as after a few hours or not until several weeks later. Food can also become contaminated by bacteria within our homes. It is common for people to carry bacteria such as Staphylococcus aureus in their nose, throat or mouth, which can contaminate food through coughs, sneezes and being spread from our hands. This bacteria can multiply on certain foods and produce a toxin that causes food poisoning. Foods that are not cooked after handling, such as sliced meats, puddings, pastries, and sandwiches, are especially risky.

Foodborne protozoa

Protozoa are single celled parasites and several types can be found in food or drink. Toxoplasma gondii can be found in raw meat but it is killed by thorough cooking. Because some protozoa are good at surviving in water, drinks can also be a route of infection. Food can become contaminated with some of these parasites during processing or production.

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Cryptospridium oocysts (green) with nuclei stained blue. Dr. Alison Burrells, Moredun Research Institute.

Foodborne viruses

Norovirus, Charles D. Humphrey, Centers for Disease Control and Prevention

18 % of UK food poisoning is thought to be caused by viruses. These viruses do not replicate in food but they are highly contagious and can remain viable (infectious) outside the body for long periods of time, even months. Foodborne viruses originate in the human or animal gut and transmission often occurs because food is contaminated by an infected person, due to poor hygiene.

Viruses that are associated with foodborne disease include norovirus, which is the biggest cause of gastrointestinal disease in the UK, and hepatitis A and hepatitis E, which affect the liver.

How to reduce the risk

To lower the risk of infection and protect you and your family against infectious foodborne disease there are certain things you can do in your own kitchen. This includes:
• cooking food properly to ensure that harmful microbes are killed
• chilling some foods to stop microbes from growing
• keeping utensils clean and washing and drying your hands properly
• taking care not to spread microbes around the kitchen by cross-contamination.

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Natural toxins from microbes

Microbes can also cause health problems through the production of toxins, known as natural toxins. These toxins are produced by fungi and phytoplankton and they can accumulate in certain types of food. Foods that may contain natural toxins include some cereals and various types of shellfish.

Other sources of infection

Many farm animals, wild animals and pets carry microbes that cause foodborne disease, so people can also become infected through touching infected animals or coming into contact with their faeces (poo). These bacteria can also survive in water that has come into contact with animal faeces so people can be infected from drinking, swimming or playing in contaminated water, such as ponds or streams. You can also become infected from contact with infected people, particularly if you don't wash your hands thoroughly after using the toilet or before handling food.

Antibiotic resistance

Antibiotics are used to slow down or stop bacteria from growing, but bacteria can become resistant to these drugs and some infections can no longer be treated, which is very worrying. Bacteria that have become resistant to many antibiotics are sometimes known as "superbugs". Resistance has accelerated due to overuse or mis-use of antibiotics and this is a major threat to global health. It is vital that we use antibiotics properly so we can limit the rate that resistance develops.