Bacterial
Campylobacter
Campylobacter can be found in raw poultry and meat,
unpasteurised milk and untreated water. Birds pecking bottle tops
on the doorstep can contaminate pasteurised milk. Campylobacter is
the most common identified cause of food poisoning as only a small
number of bacteria are required to cause illness. Thorough cooking
and pasteurisation of milk will destroy Campylobacter.
Salmonella
Salmonella has been found in raw meat, poultry and eggs, raw
unwashed vegetables, unpasteurised milk and dairy products and many
other types of food. It is found in the gut and faeces of animals
and humans. Salmonella is the second most common cause of food
poisoning although usually large numbers are required to cause
illness. Salmonella can survive when refrigerated although it is
unable to multiply through cooking and pasteurisation.
Staphylococcus aureus
Staphylococcus aureus may be found on the skin, in infected cuts
and boils and in the nose. It may also be found in unpasteurised
milk. It can be transferred to food via hands or droplets from the
nose. Staphylococcus aureus Food poisoning follows the consumption
of heavily contaminated food, where bacteria have multiplied and
produced a toxin, which causes illness when the food is consumed.
Staphylococcus aureus survives when refrigerated although it does
not multiply. Pasteurisation of milk and cooking of food destroy
the bacteria, but the toxin may survive these processes. The main
foods associated with illness are cooked meats, poultry and foods
that are handled during preparation without subsequent cooking.
Bacillus cereus
Bacillus cereus is found in soil and dust. It is often found in
rice dishes, occasionally pasta, meat or vegetable dishes, dairy
products, soups, sauces and sweet pastry products where these have
not been cooled quickly and effectively after cooking and during
storage. A small number of bacteria can cause illness, so
cross-contamination can lead to illness. The bacteria can form
spores; they are not easily destroyed by heat and will survive
cooking of food. If food is cooled slowly or kept warm for some
time before serving, the spores will germinate and produce
bacteria. Bacteria can multiply rapidly at these temperatures and
produce a very heat resistant toxin, which will not be destroyed by
subsequent reheating.
E. coli
E. coli is a widespread organism that is normally found in the
guts of animals and humans. There are many different types, some of
which are capable of causing illness. One uncommon type, which can
cause serious illness, is Verocytotoxin producing E. coli O157 that
has been found in raw and undercooked meats, unpasteurised milk and
dairy products, raw vegetable and unpasteurised apple juice. A
small number of bacteria can cause illness, therefore
cross-contamination can lead to illness. The bacteria can survive
refrigeration and freezer storage, but thorough cooking of food and
pasteurisation of milk will kill them.
Clostridium perfringens
Clostridium perfringens is excreted by a wide range of animals.
It can be found in soil, animal manure, sewage and also in raw meat
and poultry. Clostridium perfringens produces spores, which may or
may not be killed during cooking. If food is allowed to cool
slowly, the spores germinate and produce bacteria, which grow
rapidly. These bacteria may not be killed if the food is not
reheated until it is piping hot. It is particularly associated with
gravies, cooked meat dishes, stews and pies and very large joints
of meat and poultry.
Listeria
Listeria is widely present in the environment. It is found in
soil, vegetation, raw milk, meat, poultry, cheeses (particularly
soft mould-ripened varieties) and salad vegetables. It is also
found in the guts of animals and humans. One type, Listeria
monocytogenes, can cause illness in humans. Listeria monocytogenes,
unlike most other food poisoning bacteria, can grow at low
temperatures, even in the fridge. Thorough cooking of food and
pasteurisation of milk will destroy Listeria.