Download 1 - Bacteria.ai - The Food Safety System

HOT
TOPICS
No:001
A Beginners Guide To Bacteria
This hot topic will provide you with a basic understanding of Bacteria. It will serve as an introduction to
the subject and take you through the key principles of what bacteria are, how they develop and what
harm they can cause. Use this to brief your workers about bacteria and their effects.
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What are bacteria?
Bacteria are single cell micro-organisms that exist virtually
everywhere. They can be found on humans, food, in the
ground, in the air and in water. Most bacteria are harmless to
humans, some are actually essential as they break down
decaying matter in the body and others are helpful to us and
are used in the food industry in the production of cheese and
yoghurt. Some however can cause spoilage of food and others
can cause illness including food poisoning.
Definition
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Cell Wall – the rigid shell that gives the bacterium its
shape
Cell Membrane – controls the passage of waste and
nutrients in and out of the bacterium
Cytoplasm – the main body of each bacterium
Nuclear Material – effectively the brain of the bacterium
Flagella – attachments to the outside of the bacterium
that allow it to move in liquids
Below is a very simplified version of the structure of a bacterium
Cytoplasm
Nuclear Material
Cell Wall
Bacterium: One or a single
eg: a bacterium is very small
Bacteria: Multiple bacterium
eg: bacteria are very small
Cell Membrane
Flagella
se by the naked
Bacteria are incredibly small, and cannot be seen
eye. They vary in size from approximately 0.001mm to
0.003mm. Although you cannot see individual bacterium large
numbers can cause visible effects on food such as
discolouration, slime or odour
What do bacteria look like?
If you could see bacteria you would notice that they vary in
shape considerably. There are four main shapes:
How do bacteria multiply?
Bacteria multiply by splitting into two. The time it takes for each
bacterium to divide depends on the temperature and the food
available to it. Food poisoning bacteria are generally thought to
divide every 20 minutes in ideal conditions. However if
o
temperatures are kept low (below 10 C) division can take up to
10 hours.
As a rough guide, if a food item is contaminated with 1000
bacteria per gram of food and the conditions are ideal for the
bacterial to divide. You will have 1,000,000 bacteria within 2
hours. This number of bacteria is likely to cause food poisoning
What makes bacteria multiply?
Cocci:
are spherical in shape
Rods:
are shaped like a sausage
Bacteria responsible for food poisoning need the following
conditions to enable them to grow and, in some cases, produce
toxins.
Definition
Spirochaetes:
are spiral in shape
Vibrios:
are shape like a comma
Although shapes vary, all bacteria have a similar structure and
all have 5 key features:
Toxins:
Food poisoning bacteria
produce toxins, these are
effectively poisions and
can be produced in food
or inside your body
Copyright 2012 Stortfood Ltd. Registered Business
Busine (07883802)
A Beginners Guide To Bacteria
Warmth:
The best temperature for bacteria to multiply is around the
o
same temperature as the human body (about 37 C) although
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they will multiply quickly from 20 C to 50 C. To prevent growth
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of bacteria on food it must be kept below 5 C or above 63 C.
This temperature range is often referred to as “The Danger
Zone”
Warm rooms are ideal for bacterial to multiply, but most won’t
o
o
multiply in a refrigerator that runs between 1 C and 4 C and
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none will multiply in a freezer (-18 C) although many will survive
and start multiplying when the food thaws.
Some bacteria are able to produce spores which protect them
against adverse conditions such as high and low temperatures.
Once the favourable temperature returns the spores release the
bacteria which can then start to grow
Food & Moisture:
Bacteria prefer high protein food such as meat, poultry and
dairy products. Food such as dried milk powder, gravy powder
or even dried egg do not provide the conditions suitable for
growth, that is whilst they remain a powder. Once liquid is
added any bacteria present will begin to multiply.
Other foods which do not support the multiplication of bacteria
include products high in sugar, high in salt or high in
preservatives or acids.
Time:
Given the right conditions of food, moisture and warmth,
bacteria can divide into two every 10 minutes. If there is enough
time a few bacteria can multiply to such as extent that there is
enough to cause severe food poisoning. For this reason, high
risk foods such as meats, fish, dairy products and poultry are
o
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not left in the danger zone (5 C to 63 C) for any longer than is
absolutely necessary.
Important
It is often assumed that bacteria require oxygen to survive and
to multiply. This is not always the case. Some bacteria thrive
without the need for oxygen and some can survive with and
without oxygen. Correct cooking is the only way to ensure
bacteria are killed off.
What Are High Risk Foods?
High risk foods are generally ready to eat foods which by their
nature support the multiplication of harmful bacteria and are
intended to be consumed with no further preparation. Such
foods include:
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Cooked meat and cooked poultry
Cooked meat products including meat pies, gravy,
stews, spreads and stock
Milk, cream, artificial cream, custard and any dairy
product
Eggs and products made from raw egg such as
mayonnaise and hollandaise sauce.
Shellfish and other seafood including oysters, prawns
and crabs
Cooked rice
What is food poisoning?
Food poisoning is an acute illness which usually occurs within 1
to 36 hours of eating contaminated food. Symptoms can last
from 1 to 7 days and can include: stomach cramps, diarrhoea,
vomiting, nausea and fever.
Food poisoning is caused by:
• Bacteria and their toxins
• Viruses
• Chemicals such as insecticides & cleaning agents
• Metals such as mercury, lead and copper
• Poisonous plants such as toadstools
Bacterial food poisoning is by far the most common and some
instances can cause death. A large number of bacteria are
usually involved and this normally requires them to multiply
within food.
What Are The Key Food Poisoning Bacteria?
Salmonella:
Source – Raw meat, milk, eggs, raw poultry, pets, rodents,
flies, sewage/water
Onset Period – 12 to 36 hours
Symptoms – Abdominal pain, diarrhoea, vomiting and fever
Clostridium Perfringens:
Source – Animal and human excreta, soil, dust, insects and
raw meat
Onset Period – 12 to 18 hours
Symptoms – Abdominal pain and diarrhoea. Vomiting is rare
Staphylococcus Aureus:
Source – Human nose, mouth, skin, boils and cuts. Raw milk
from cows and goats
Onset Period – 1 to 7 hours
Symptoms – Abdominal pain, vomiting, prostration and
subnormal temperatures
Clostridium Botulinum:
Source – Soil, fish, meat and vegetables
Onset Period – 12 to 36 hours
Symptoms – Difficulties in swallowing and breathing, double
vision, paralysis. Fatalities are common and recovery of
survivors takes many months
Bacillus Cereus:
Source – Cereals, especially rice
Onset Period – 1 to 5 hours
Symptoms – Vomiting, Abdominal pain, and some diarrhoea.
Definition
Onset Period:
The time it takes
before symptoms
start to appear
Copyright 2012 Stortfood Ltd. Registered Business (07883802)
A Beginners Guide To Bacteria
Food-bourne Diseases
Bacteria in food is not just the cause of food poisoning. Other
illness can be caused by bacteria in food. These are known as
food-bourne diseases. Such illnesses include:
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Typhoid
Paratyphoid
Tuberculosis
Dysentry
Brucellosis
There are three specific types of bacteria known to cause foodbourne illness:
Campylobactor:
Source - Raw poultry, raw meat, raw milk, farm animals,
sewage and birds.
Onset Period – 2 to 5 days
Symptoms – Fever, bloody diarrhoea, abdominal pains and
nausea
Unlike food poisoning, only small numbers of bacteria are
required to cause these illnesses and multiplication within the
food is not necessary.
The bacteria responsible are found in the gut of man amongst
other places and chain of infection is the same as that involved
in food poisoning. This is known as the faecal – oral route.
Note - More cases of illness are caused by this bacteria than by
salmonella
Listeria:
Source - Animals, humans, sewage and raw milk.
Onset Period – 1 to 70 days
Symptoms – Flu like symptoms including fever and diarrhoea
BACTERIA
IN
FAECES
Note - Listeria is known to multiply at temperatures lower than
o
3C
E.coli O157:
Source – Intestines of cattle, sheep and human, sewage, meat
and raw milk.
Onset Period – 3 to 4 days
TRANSFERRED
VIA HANDS/
SEWAGE
Symptoms – Nausea, diarrhoea and severe abdominal cramps
Note - NE.coli O157 is known to cause kidney failure in children
and fatalities in the elderly.
Remember
BACTERIA
GETS ON
TO FOOD
It is impossible to eliminate all food poisoning bacteria from food
businesses and they will be present from time to time therefore
it is vitally important that:
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FOOD IS
CONSUMED
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Bacteria are denied the chance to contaminate high risk
food
All food should be protected by storing at the correct
temperatures at all times
Work surfaces and equipment must be kept clean using
appropriate cleaning and anti-bacterial agents
Good hand washing and personal hygiene practices
must be observed at all times
Workers returning from foreign holidays should be
assessed to ensure they are fit to work
BACTERIA
CAUSES
ILLNESS
IN MAN
Copyright 2012 Stortfood Ltd. Registered Business (07883802)