Microorganisms - Food Poisoning

Food poisoning is an intoxication resulting from the consumption of food. It is a part of foodborne illnesses that is caused by toxins from bacteria, fungi, virus, parasites and by natural toxins.




Food poisoning is an intoxication from several agents e. g. bacteria, virus, fungi, parasites and plants. Under the right conditions food is safe but some circumstances can result in food poisoning. Knowledge of toxic plant and animal ingredients can save lives. For example nobody would eat a flyagaric (kind of toadstool with red hat and white dots) or a toxic fish.

Some bacteria build exotoxins which can harm human beings. By destroying the bacteria its toxin is set free. If one picks up some bacteria with food toxin are set free within his or hers body. You can also pick up food with free toxin already in it like mycotoxin (toxin produced from fungi). To avoid food poisoning do not eat food with toxic moulds as mycotoxins may be present.

Staphylococcus aureus (small round bacteria) produces a toxin which causes vomiting and diarrhea without fever. Salmonella (a small rood) intoxication causes basically the same symptoms but with fever and a longer incubation time (the time from picking up the bacteria until symptoms show). Both can be found in eggs and food prepared with raw eggs (tiramisu, crème filled cake). You cannot smell or taste these bacteria and they are invisible to the human eye. So it is better to know rules of hygienic food preparation and storage. Both kind of bacteria cannot grow by temperatures under 4 – 7 °C. Salmonella is often found on a surface of raw poultry. For preparing food, slice vegetables and poultry on different plates. This prevents contamination of vegetables by raw poultry.

There are many other bacteria which cause food poisoning. Clostridium botulinum (a spore forming rood) is anaerobic and can survive in canned food. It produces one of the strongest neurotoxin known to mankind. Their spores survive high temperatures. For health protection a cooking time for at least 10 minutes at 100 °C is necessary.

Viruses, finally, need a living cell to survive. They are stuck in the food without being able to reproduce or grow. Transported with food into the human body, viruses occupy the body cells. Virus reproduction and toxin production starts. This is the reason why a small number of particles can be already very infectious. Heating destroys most viruses. A very common virus is the norovirus. In the UK it is called the “Winter Vomiting Bug”, but infections are observed at all times of the year. Also, there are many outbreaks on cruises. It is a common infection in places with many people (kindergartens, schools, universities, camps). Transmissions can occur by water, fruits, meat, and vegetables as well as directly from human to human.

If you are not sure you can trust some food follow the rule:

“Cook it, peel it or forget it”



Figure 1: Old, abandoned refrigerator on the street in the summertime. If you eat something from this refrigerator you most certainly will get food poisoning. [source: D. Graubaum, Berlin]













This text was prepared by Diana Graubaum, Department of Food Microbiology, Beuth University of Applied Sciences Berlin, Berlin, Germany.

For further questions please refer to: graubaum@beuth-hochschule.de