In most types of food poisoning pathogenic bacteria cause illness in a person by attacking the cells of the body. This may take some time and the period of time between someone eating contaminated food and becoming ill (you will remember from Part A) is known as the incubation or onset period. This can be many hours or even two or three days.
However, in the case of Staphylococcus aureus food poisoning (more about this bacteria shortly) the illness is not caused by the bacteria themselves but by a poison formed in the food whilst the bacteria are growing on it. Such a poison is known as a toxin.
Toxins
A toxin
is another name for "a poison formed by pathogenic
bacteria in the food". So whenever you see the word toxin just think,
"poison".
TOXIN
=
Because the poison is already present in the food when it is eaten, the consumer will become ill more quickly than in other types of food poisoning - usually between one to six hours.
Unfortunately, some toxins are heat resistant and if they are already in food will not be destroyed by cooking, making them very dangerous.
Spores
Other things that can be a problem for food handlers are spores.
Spores "are a form of bacteria that can survive difficult conditions such as high temperatures,
dry conditions or the presence of disinfectants".
Only certain types of food poisoning bacteria can form spores, such as Clostridium perfringens, (more about this particular bacterium later).
The way that spores work is like this. When conditions become difficult, such as very hot or dry, the bacterium starts to form a protective coating around itself. When completed, this coating can guard the organism from high temperatures, drying, freezing or even chemicals like salt or disinfectant (some spores can survive boiling for many hours!) During the time the bacterium is protected by the spore it is inactive and we say that it is dormant.
When conditions improve for the bacterium, then the hard coating of the spore will split and a new normal bacterial cell will emerge and start multiplying as if nothing had happened. This process of the spore splitting and a normal bacterial cell emerging is called germination and after it has occurred food poisoning bacteria are able to multiply and cause illness again.
As we will see later, spores are a particular worry whenever food is cooked in advance and then cooled slowly and served cold or re-heated later before service.
Whilst most food poisoning bacteria make people ill when the bacteria themselves enter the body and affect the cells of the digestive system, others produce poisons that cause illness. These poisons are known as toxins and some are resistant to heat and will survive cooking temperatures.
Certain bacteria are able to produce a hard coating to protect themselves from unfriendly conditions like heat, dryness, cold and chemicals. In this form the bacterium is known as a spore. Spores can survive high cooking temperatures. However, if good conditions return, the spore coating splits and a normal bacterium reappears and is able to multiply and cause food poisoning.