NFS 220 Lecture Notes - Lecture 3: Giardia Lamblia, Foodborne Illness, Pathogenic Bacteria
11 Jun 2018
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Microbes and Foodborne Illness
Microbes are living things that are often too small to be seen without the help of a
microscope. There are any different types of microbes including bacteria, viruses, parasites,
protozoa and fungi. Some microbes and beneficial to us such as some types of yeast, moulds
and bacteria that produce foods like yogurt, cheese, sauerkraut, beer and wine; and those that
live in our intestines and help us digest food.
Some microbes can cause illness and even death. These microbes are called pathogens, which
means something that produces sickness.
Bacteria are all around us. Most bacteria are harmless or even helpful to humans, but some
can make us very sick. Pathogenic bacteria such as Campylobacter, E. coli, Listeria and
Salmonella that can live and grow in food are among the most frequent of foodborne illness.
Viruses are smaller than bacteria and frequently cause illness. Viruses that are harmful to
humans may be found in contaminated food but will not grow in food. Hepatitis A and the
Norovirus are examples of viruses that are transferred from food handlers to food often
because of improper handwashing.
Parasites live on or inside another animal or person and are dependent on the host for
nutrients. Parasites such as trichinella might be found in undercooked pork or other meats,
and roundworms might be found in raw fish such as sushi or sashimi.
Protozoa are one celled animals. An example of protozoa is Giardia lamblia that may be
found in rivers, lakes, streams and shallow wells. Giardia’s, one of the most frequent causes
of non bacterial diarrhea in North America, may be caused by washing produce in water
contaminated with Giardia lamblia.
Fungi grow on animals, plants, humans, decaying organic matter, in fact anywhere that is
warm and damp. Many fungi are beneficial, but some fungi can spill foods. It is important to
remember that scraping or cutting mould off of food may not make the food safe. The mould
may have produced toxins that will remain in the food.
Spores and Toxins
Some types of bacteria are able to produce a hard coating to protect themselves from stressful
conditions such as extreme heat, dryness, cold and chemicals. A bacterium with this
protective coating is called a spore. Spores can survive high temperatures, drying, boiling,
freezing or even chemicals like cleaning agents and disinfectants. When conditions for
bacterial growth improve, for example when cooked food containing the spores is removed
from the heat and left at room temperature, the spore coating splits open and a normal
bacterium emerges and begins to multiply in the food. Spores are a particular concern when
food is cooked in advance; allowed to cool too slowly, and then served cold or improperly re
heated later.
When some bacteria multiply they produce toxins which will make people sick when
consumed. Some of these toxins may be destroyed by cooking, but others are heat resistant
and will survive even high cooking temperatures. The production of toxins can be controlled
by paying close attention to time and temperature when storing and preparing food.
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Document Summary
Microbes are living things that are often too small to be seen without the help of a microscope. There are any different types of microbes including bacteria, viruses, parasites, protozoa and fungi. Some microbes and beneficial to us such as some types of yeast, moulds and bacteria that produce foods like yogurt, cheese, sauerkraut, beer and wine; and those that live in our intestines and help us digest food. Some microbes can cause illness and even death. These microbes are called pathogens, which means something that produces sickness. Most bacteria are harmless or even helpful to humans, but some can make us very sick. Pathogenic bacteria such as campylobacter, e. coli, listeria and. Salmonella that can live and grow in food are among the most frequent of foodborne illness. Viruses are smaller than bacteria and frequently cause illness. Viruses that are harmful to humans may be found in contaminated food but will not grow in food.
