Food poisoning happens when food has not been handled correctly – resulting in the growth of pathogens. When this food is consumed it can then cause a food-borne illness. Cooking food will often kill these bacteria but contamination might still happen after cooking.
Food poisoning can also happen if food processing equipment and machinery is not cleaned correctly leaving bacteria growing on surfaces as biofilms. Most food-borne pathogens have the ability to form biofilms, and this enables them to contaminate food. Procedures in place to clean food-contact surfaces often include daily sanitisation, detergents and other chemical reagents. However, biofilms often persist on these surfaces.
You might have heard about raw chicken causing food poisoning. This is due to contamination of the meat by Salmonella or Campylobacter. If these pathogens are not killed by cooking then they can cause infection when eaten. Bacteria can also contaminate vegetables. For example, Listeria has been associated with frozen sweetcorn.
Bacteria can form biofilms on food, transportation containers or even the water that the food is washed in. When people eat contaminated food they can develop gastroenteritis, diarrhoea and a fever. In some people this can lead to more serious illness.
Biofilms are a frequent source of contamination within the food industry and cause problems in meat and poultry processing, brewing, and even vegetable processing. Therefore, biofilms have a huge impact on the running costs and efficiency of a business in addition to the potential health risks. Methods for detecting contamination on machinery include sensors that measure thermal conductivity and heat variations; they can detect biofilms even when they are only a few micrometres deep. Despite ‘Clean-In-Place’ protocols involving a number of automated cleaning steps, biofilms can be resistant, requiring harsh disinfectants such as hydrogen peroxide, sodium hypochlorite and ozone for effective removal.
Common Foodborne Pathogens:
Listeria monocytogenes causes listeriosis, a severe foodborne illness particularly dangerous for the elderly, the immunocompromised, pregnant women and their unborn infants. Public Health England have estimated that there are between 160 and 192 cases a year (2013-17). Large outbreaks have occurred. In 2015 there was a large outbreak of Listeria associated with frozen sweetcorn. The source was a sweetcorn processing factory in Hungary (McLauchlin et al., 2021).
Salmonella enterica is a major global cause of food poisoning and is capable of forming biofilms on various surfaces including plastic and steel. Salmonella also causes outbreaks: in 2013-14 Salmonella enterica was responsible for an outbreak in Germany that affected 145 elderly people and was linked to contaminated pork sausages. There are many types of Salmonella and another strain caused an outbreak in Norway (2013) as a result of contaminated ‘ready to eat’ salad in bags (Vestrheim et al., 2015).
Escherichia coli is a Shiga toxin-producing bacterium that can cause very serious disease. In 2016 an outbreak in the UK was linked to mixed salad leaves imported from the Mediterranean region. In total 161 cases were identified and two people died (Public Health England, 2016).
How does produce get contaminated?
Despite there being many protocols in place to protect people from food-borne pathogens, occasionally bacteria get through. Contamination can occur at any stage of food processing from crop irrigation through to post-harvest washing, cutting and packaging. All these processes require machinery or workers and all can represent sources of bacteria capable of contaminating food.
How does eating chicken give you food poisoning?
The most common cause of bacterial food poisoning from chicken is Campylobacter which usually lives within the gut of chickens, other poultry and cattle. It does not cause disease in poultry but remains present in their meat. If not cooked properly then people will eat live Campylobacter in the meat. These bacteria then replicate and invade the gut, where the immune system attacks and causes inflammation. This is known as a gastrointestinal infection and symptoms of this are diarrhoea, cramps, fever and pain, all of which occur 24-72 hours after infection. Whilst the sufferer usually gets better on their own, there can be serious consequences.
Further reading on biofilms and food poisoning
McLauchlin, J., Aird, H., Amar, C., Barker, C., Dallman, T., Lai, S., Painset, A. and Willis, C. (2021) ‘An outbreak of human listeriosis associated with frozen sweet corn consumption: Investigations in the UK’, International Journal of Food Microbiology, vol. 338, https://doi.org/10.1016/j.ijfoodmicro.2020.108994
Vestrheim, D.F., Lange, H., Nygård, K., Borgen, K., Wester, A.L., Kvarme, M.L. and Vold, L. (2015) ‘Are ready-to-eat salads ready to eat? An outbreak of Salmonella Coeln linked to imported, mixed, pre-washed and bagged salad, Norway, November 2013’, Epidemiology & Infection, vol. 144(8), pp. 1756-60 https://doi.org/10.1017/S0950268815002769
Public Health England (2016) E.coli 0157 national outbreak update, available at https://www.gov.uk/government/news/update-as-e-coli-o157-investigation-continues
Salmonella biofilms make these varied and widespread threats to public health around the world even more of a problem. Some animals (e.g. chickens, birds, snakes, frogs), can have Salmonella living in their gut without causing them any infection – but these bacteria could still infect you. That’s why you should always wash your hands after touching […]
Listeria have been found on many different surfaces, and commonly in animals, soil, water, sewage, vegetation, vegetables and faeces. All types of raw food have the potential to be contaminated with Listeria, and some ‘ready-to-eat’ food products are of a concern. Listeria is a problem in the food industry because eating food contaminated with some types of Listeria, e.g. Listeria monocytogenes, can […]