Important food poisoning bacteria

Important food poisoning bacteria

Salmonella

Sauces

The intestines of ill people and carriers, animals, birds and animal food, raw meat, raw poultry, raw milk, raw eggs, pets, rodents, terrapins, faeces, insects and sewage/water.

Common food vehicles

Under cooked or contaminated cooked meat and poultry, raw milk, raw eggs and under cooked foods using raw eggs in their preparation, for example, mayonnaise, mouses and tiramisu, cut melon, bean sprouts, dried coconut, salad vegetables and chocolate.

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Onset period

6 to 72 hours, usually 12 to 36 hours. Ineffective food poisoning (exdotoxin in the intestine.)

Symptoms and duration of illness

Abdominal pain, diarrhoea, nausea, vomiting, fever and headache. The duration is usually 1 to 7 days. Occasionally deaths are recorded usually involving the elderly, the very young and people who are already ill.

Specific characteristics

Usually requires millions of bacteria to cause illness. However, out breaks involving low numbers have been recorded in food vehicles with high fat content, such as chocolate, milk and cheese. In  such cases the incubation period may be up to 10 days. Salmonella multiplies from 7°C to 47°C under aerobic or anaerobic conditions.

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Specific control measures

  • Sterilise animal feed and avoid subsequent contamination.
  • Segregate ill animals..
  • Hygienic transport from farm to abattoir (avoid overcrowding)
  • Hygienic slaughtering.
  • Prevent cross-contamination between raw and high-risk food from storage through to serving.
  • Complete thawing of frozen poultry.
  • Thorough cooking to above 75°C . Use heat-treated milk.
  • Double-wash raw, ready-to-eat salads and fruit.
  • High standards or personal hygiene, especially hand washing after visiting the toilet and before handling hugh-risk food.
  • Exclude cleaning and disinfection.
  • Use pasteurised egg.
  • Chlorination of water.
  • Safe sewage disposal.
  • Exclude pests and animals from food premises or food contact.

Clostridium perfringens

Sauces

Intestine of humans and animals, faeces and sewage, soil, dust, insects, raw meat and poultry.

Common food vehicles

Rolled joints, casseroles, stews, sauces, mince and meat pies when cooking has removed oxygen.

Onset period

4 to 24 hours, usually 8 to 12. Infected food poisoning caused by an enterotoxin in the intestine.

Symptoms and duration of illness.

Abdominal pain and diarrhoea. Vomiting is rare. Symptoms usually last 12 to 48 hours.

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Specific charateristics

Clostridium multiples between 15°C and 52°C under anaerobic conditions. The optimum temperature is between 43°C and 47°C. At 46°C Clostridium perfringens can double every ten minutes. It  produces spores which can survive high temperature and dehydration. Illness usually results from consuming millions of organisms. Spores germinate as a result or normal cooking temperatures and long, slow cooling allows the vegetative bacteria to multiply rapidly. Mild reheating may not destroy these bacteria.

 Specific control measures

  • Separate raw and high-risk foods, especially meat and vegetables.
  • Use ready prepared and washed root vegetables to avoid bringing soil into the kitchen. Double-wash- salad vegetables such as lettuce.
  • Strict temperatures control.
  • Cook or reheat food to at least 75°C and then serve immediately or sore above 63°C.
  • Maximum joint sizes 2.25 kg.
  • Rapidly cool joints, sauces, pies, ect. especially between 60°C and 20°C and then refrigerate.
  • High standards of personal hygiene, especially hand washing after visiting the toilet and before handling high-risk food.
  • Exclude symptomatic food handlers.
  • Effective cleaning and disinfection.

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Staphylococcus Aureus

Sources

Human nose, mouth, skin, hands, boils, scratches, spots and cuts, especially if septic. Raw milk from cows or goats with mastitis, or products such as cheese made from raw milk. Up to 40% of the population may carry Staphylococcus aureus in their mouth or nose and up to 15% on their hands.

Common food vehicles

Milk and dairy products, trifles and cream desserts, custard-type products, cold cooked meat and poultry, salads, peeled cooked prawns, lasagna and fermented sausage.

Onset period

1 or 7 hours, usually 2 to 4 hours. Heat-resistant exotoxin produced in food (can survive boiling for 30 minutes). Toxic food poisoning.

Symptoms and duration of illness

Abdominal pain, nausea, mainly vomiting, diarrhoea, collapse and occasionally subnormal temperatures. The duration is usually between 6 and 24 hours.

Specific characteristics

Sporadic cases may be common but are rarely notified and are not recorded. Staphylococcus multiplies in aerobic or anaerobic conditions between 7° C and 48°C. Can tolerate relatively high salt content. Usually requires millions of organisms to produce sufficient toxin to cause illness. Is usually harmless when not in food. Toxin may survive  boiling for up to 30 minutes.

Specific control measures

  • High standards or personal hygiene, especially hand washing before, and frequently whilst, handling high-risk food and not touching the mouth, nose or hair during food preparation.
  • Avoid handling high-risk food, where possible use utensils.
  • Exclude food handlers with respiratory infections especially those involving coughing or sneezing; boils or septic cuts; or skin infections that encourage scratching or flaking.
  • Avoid consuming raw milk or products made from raw milk.
  • Prevent cross-contamination (it may be present on chicken skin).
  • Cover cuts with waterproof dressings.
  • Strict temperatures control of high-risk food.
  • Pre-cool salad ingredients.

Bacillus cereus

Sources

Cereals, especially rice, cornflour, dried food, spices, dust, vegetation, soil and intestinal tract of humans.

Common food vehicles 

Reheated rice, cornflour products, foods containing spices, vanilla slices, custards, cream pastries, soups, vegetable dishes, meats and starchy foods, e.g. pasta and potatoes.

Onset period

Usually 1 to 5 hours. Exotoxin produced in food, which can survive temperatures of 126° C for up to 1.5 hours. Toxic food poisoning.

Symptoms and duration of illness

Nausea, vomiting, abdominal pain and some diarrhoea. The duration is between 1 and 5 days, usually 12 to 24 hours.

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Specific characteristics 

Bacillus cereus is a spore former, which produces an exotoxic in food and multiplies under aerobic conditions. Both the spores and the exotoxic will survive normal cooking temperatures.  Millions of organisms are usually required to cause illness and bacteria multiplying between 4.4°C and 48°C with an optimum between 28°C and 35°C. There is a second type of Bacillus cereus, which resembles Clostridium perfringens in that it produces an enterotoxin in the intestine. The onset periods is 6 to 24 hours and symptoms are primarily abdominal pain  and diarrhoea with some vomiting and fever.

Specific control measures

  • Rapidly cool cooked food and store under refrigeration.
  • Cooking must be thorough and, if unavoidable, reheating should be carried out at least to 75°C. Eat immediately or hot hold above 63°C.
  • Particular care with rice which should never be reheated more than once.
  • Avoid cross-contamination.

Clostridium Botulinum

Sources

Soil, vegetables, intestinal tract of fish and mammals.

Common food vehicles

Low-acid processed food, vacuum packed meat or fish, smocked or fermented fish, bottled vegetables, products containing spices, garlic, oil, mascarpone cheese and dried milk.

Onset period

Two hours to eight days but usually 12 to 36 hours. A heat-sensitive neurotoxin which affects the nervous system, os produced in food.The result is toxic food poisoning.

Symptoms and duration of illness

Difficulties in swallowing, talking and breathing. Double vision and muscular paralysis. Diarrhoea at first, followed by constipation. Fatalities are common and survivors may take several months t recover.

Specific characteristics 

Clostridium botulinum multiplies between 3.3°C and 50°C under anaerobic conditions. Heat-resistant spores are produced and the safety of canned food is based on the destruction of these spores, i.e. 121°C for a minimum of three minutes (botulinum cook).

Specific control measures

  • Prevent post-process contamination of cans or vacuum packs low-acid food.
  • Ensure time/temperature combinations used in canning will destroy and spores of Clostridium botulinum that may be present.
  • Do not use brown cans or cans with badly damaged seams.
  • Use of preservatives such as nitrite in vacuum packs of meat.
  • Thorough cooking of food immediately prior to consumption will probably destroy any toxin that is in the food.
  • Smoked fish should be produced in accordance with good manufacturing practices and preferably stored in a freezer to prevent multiplication and toxin production.
  • Strict attention to the shelf life of vacuumed packs.
  • Strict temperature control.

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