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.