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Appendix IV

General Principles in Prevention of Bacterial Food Poisoning

What is Food Poisoning?

Food poisoning is caused by the consumption of food or drinks contaminated with pathogens (including bacteria, viruses and parasites), bacterial or biochemical toxins or toxic chemicals.  Patients usually show gastrointestinal symptoms like nausea, abdominal pain, diarrhoea and vomiting, although other symptoms like fever may also develop.  The incubation period varies from hours to days depending on the causative agent.

Common Types of Bacterial Food Poisoning in Hong Kong

In Hong Kong, bacterial food poisoning caused by pathogenic bacteria is the commonest type of food poisoning.  There are various kinds of bacterial food poisoning, but the following are the most prevalent:

Name of Bacteria Common Foods Involved
Salmonella spp. Raw or undercooked egg and egg products (e.g. Tiramisu); undercooked meat, poultry and their products (e.g. barbecued and preserved meat, goose intestines, etc.).
Staphylococcus aureus Foods which have been subject to a large amount of handling with no subsequent cooking or reheating (e.g. lunch boxes, cakes, pastries, sandwiches, etc.).
Vibrio parahaemolyticus Raw or undercooked seafood, shellfish, marine products and salted food (e.g. jellyfish, cuttlefish, salted vegetables and smoked knuckles, etc.).
Bacillus cereus Leftover cooked rice, fried rice, meat products and vegetables.
Clostridium perfringens Cross-contaminated and inadequately cooked meat and meat products (e.g. stew and meat pies, etc.).

[Note: For further details about the above bacterial food poisoning and other types of food poisoning that may be found in Hong Kong as well as their prevention, please refer to Appendix V.]

Common Contributing Factors to Bacterial Food Poisoning

  1. Contamination of Cooked Food

    Cooked food has been contaminated by food handlers, raw food, food contact surfaces or pests.
  2. Improper Storage of Cooked Food

    Cooked food has been stored between 4oC and 60oC for a prolonged period.
  3. Inadequate Cooking of Food

    Raw food has not been cooked thoroughly to reduce any pathogen present.
  4. Inadequate Reheating of Cooked Food

    Cooked food has not been reheated to 75oC.
  5. Inadequate Thawing of Food Before Cooking

    Insufficiently thawed food, which still has a high bacterial count or pathogen content and which needs a longer time to reach the temperature that kills the bacteria and pathogens in cooking, has not been cooked for sufficiently long time.
  6. Preparation of Food Too Early In Advance

    Food has been prepared too early in advance but has not been stored under proper temperature control.
  7. Infected Food Handlers

    Food handlers infected with communicable diseases have engaged in handling food.
  8. Consumption of Raw Food

    Food (e.g. shrimps) that usually has a high bacterial count or pathogen content has been eaten in a raw state without cooking.
  9. Use of Unsafe Food Source

    Food has been purchased from an unapproved or unreliable source such as hawkers.
  10. Use of Leftovers

    Use of food leftovers (e.g. cooked rice) that have been stored between 4oC to 60oC for a prolonged period.

Prevention of Bacterial Food Poisoning

In principle, the best way to avoid bacterial food poisoning is to ensure safe food production.  Essential measures include:

  1. Purchase of Food
    1. Do not buy foods that are not properly protected (e.g. siu mei and lo mei that has been exposed to the open air during transportation, or cooked food that has not been covered properly).
    2. Do not purchase food from unlicensed sources, especially for cooked or cold food (because the place and ways in which they cook their foods are usually not hygienic).
    3. Do not buy any food which looks abnormal (e.g. swollen or dented canned foods).
    4. Food to be eaten raw, such as sashimi and rock oysters, should be obtained from a reliable and reputable source to ensure their quality.
  2. Handling of Food
    1. Food should be thoroughly cooked before being served to customers (both meat and marine products should be well-cooked).
    2. Cooked food should be prepared and stored separately from raw food (to avoid cross-contamination).
    3. Food handlers should thoroughly wash their hands after going to the toilet and before handling food (to prevent the soiled hands from contaminating the food). In any case, do not touch cooked food with bare hands.
    4. Anybody suffering from diarrhoea, vomiting, sore throat or inflamed wounds (unless properly bandaged with water-proof plastic tapes) should not handle or touch any food so as to prevent the food from being contaminated by food poisoning bacteria.
  3. Storage of Food
    1. Food should be served once it is prepared (that means food should be served either hot or cold. Food that is neither hot nor cold is conducive to the growth of bacteria).
    2. Leftovers should best be discarded. Otherwise, it should be properly stored in refrigerators (4oC or below) and thoroughly reheated to 75oC or above before being served to customers.
    3. Any food that is not to be served immediately should be stored at a temperature below 4oC or above 60oC. Do not store food at room temperature which is favourable to bacterial growth or production of toxins.