Transcript Types of bacteria

Types of bacteria
• Spoilage: Not particularly
harmful bacteria which cause
food to go off
• Beneficial: “Good Bacteria”
which are used to make
yoghurt and cheese
• Pathogenic: Illness causing
bacteria
In order to grow and multiply germs need:
Time
Moisture
Food
Warmth
Flies
Waiting
Remember it like this
Too
Many
In ideal conditions where there is
Moisture, Food and Warmth
(37degrees centigrade is ideal),
bacteria can double every 10 to 20
minutes. They do this by dividing
in to two. This is called
Binary Fission
These cells are beginning to divide into two
After 10 minutes
After 20 minutes
After 30 minutes
After 40 minutes
cooking chicken to a core temperature
of 75°C should kill most of the bacteria
Time : 9.30
Bacteria : 0
Time : 9.40
Bacteria : 12,000
Time : 9.50
Bacteria : 24,000
Time : 10.00 Bacteria : 48,000
Time : 10.10
Bacteria : 96,000
Time : 10.20 Bacteria : 192,000
Time : 10.30 Bacteria : 384,000
Time : 10.40 Bacteria : 768,000
Time : 10.50 Bacteria : 1.5 million
From 0 to 1,536,000 in
only 80 minutes !!!!!!
Knife
contaminated
by blood
Spore Formation
This is what happens …………..
Cell
Spore forms
in cell
Cell
disintegrates
Spore is
released
Spore starts
to germinate
Spore
continues to
germinate
Now see as, in suitable conditions, the cell
begins to divide (binary fission)………………………….
Toxins
Some bacteria release poisons known as toxins
which cause food poisoning. Some toxins,
known as exotoxins multiply in food. These
toxins are not easily destroyed by cooking and
may remain in food once they have developed.
Other bacteria produce toxins inside the human
body only after the food has been eaten. These
are called endotoxins
Food Poisoning bacteria
•Usually need millions of bacteria to cause
illness.
•The multiplication of bacteria within the
food plays an important part in the disease
Staphylococcus
Aureus
Found in human
nose and throat
(also skin)
Salmonella
Found in animals,
raw poultry and
birds
Bacillus Cereus
Found in soil,
vegetation,
cereals and
spices
Clostridium
Perfingens
Found in animals
and birds
Clostridium
Botulinum
Found in the soil
and associated
with vegetables
and meats
Salmonella
• Sources - The intestines of ill people and
carriers, animals and animal food, raw meat,
raw poultry, raw milk, raw eggs, food pests
• Common food vehicles – Undercooked or
contaminated cooked meat, raw milk and
eggs
• Onset period – 6 to 72 hours (usually 12 to
36) Endotoxin in intestine (infective food
poisoning)
Salmonella
• Symptoms - Abdominal pain, diarrhoea,
vomiting and fever. Duration is usually one to
seven days.
• Specific characteristics – Usually requires
millions of bacteria to cause illness. Multiplies
from 5°C to 47°C under aerobic or anaerobic
conditions.
Clostridium perfingens
• Sources - The intestines of humans and
animals, faeces and sewage, soil food pests,
raw meat and poultry
• Common food vehicles – Rolled joints,
casseroles, stews, sauces and meat pies when
cooking has removed oxygen
• Onset period – 8 to 22 hours (usually 12 to 18)
Enterotoxin in intestine. (infective food
poisoning)
Clostridium perfingens
• Symptoms - Abdominal pain, diarrhoea,
(vomiting is rare) and fever. Duration is
usually 12 to 48 hours.
• Specific characteristics – Usually requires
millions of bacteria to cause illness. At
46°C it can double every 10 minutes.
Produces spores. Illness caused from
consuming millions of organisms
Staphylococcus Aureus
• Sources - Human nose, mouth, skin,
hands, spots, boils, septic cuts etc
• Common food vehicles – Dairy
products. Cold cooked meat and poultry,
peeled cooked prawns
• Onset period – 1 to 7 hours (usually 12
to 18) Exotoxin produced in food. (Toxic
food poisoning)
Staphylococcus Aureus
• Symptoms - Abdominal pain, diarrhoea,
vomiting. Occasionally subnormal
temperatures. Duration between 6 and 24
hours.
• Specific characteristics – Usually requires
millions of bacteria to cause illness. Toxin
may survive boiling for up to 30 minutes.
Bacillus Cereus
• Sources - Cereals, especially rice,
cornflour, spices, dust and soil
• Common food vehicles – Reheated rice,
cornflour and spices.
• Onset period – 1 to 5 hours. Exotoxin
produced in food. (Toxic food poisoning)
Bacillus Cereus
• Symptoms - Abdominal pain, diarrhoea,
vomiting. Occasionally subnormal temperatures.
Duration between 12 and 24 hours.
• Specific characteristics – Forms spores which
survive under normal cooking conditions.
Millions required to cause illness. Bacteria
multiply between 7°C and 48°C.
Clostridium Botulinum
• Sources - Fish intestine, soil and vegetables.
• Common food vehicles –Smoked fish, bottled
vegetables.
• Onset period –2 hours to 5 days (usually 12 to
36 hours). A heat sensitive neurotoxin produced
in the food which affects the nervous system.
(Toxic food poisoning)
Clostridium Botulinum
• Symptoms - Difficulties in swallowing, talking
and breathing. Double vision and paralysis.
Diarrhoea followed by constipation. Fatalities are
common and survivors may take several months to
recover.
• Specific characteristics – Forms spores which
will survive normal cooking temperatures.
Millions required to cause illness. Bacteria
multiply between 3.3°C and 48°C.