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8 February 2013
Food Poisoning  

Causative agent and clinical features

Food poisoning is usually caused by the consumption of contaminated food or water containing various bacteria, viruses, parasites or even toxins of biochemical or chemical nature.

Causative agent

Some of the common causative agents of food poisoning include:

Causative agent : Salmonella (Bacteria)
Places where such agents are commonly found : Intestines of animals especially poultry, eggs.
Usual source of food poisoning by such agents : Inadequately cooked meat, meat products and poultry. Raw egg and egg products (e.g. puddings).
Clinical features : Common symptoms include vomiting, diarrhoea and abdominal pain, with or without fever. Serious complications, such as dehydration and septicaemia leading to death may occur when appropriate treatment is delayed, but these are rare.

Causative agent : Staphylococcus aureus (Bacteria)
Places where such agents are commonly found : Throat, nasal cavity, skin, cuts and wounds.
Usual source of food poisoning by such agents : Any food contaminated by food handlers with skin infection or nasal carriers, especially those food involving manual handling and no reheating afterwards (e.g. sandwiches, cakes and pastries).
Clinical features : Common symptoms include vomiting, diarrhoea and abdominal pain, with or without fever. Serious complications, such as dehydration and septicaemia leading to death may occur when appropriate treatment is delayed, but these are rare.

Causative agent : Vibrio parahemolyticus (Bacteria)
Places where such agents are commonly found : Marine products.
Usual source of food poisoning by such agents : Inadequately cooked marine products (e.g. jellyfish and cuttlefish), salted food (e.g. salted vegetables and smoked knuckles) or other food cross-contaminated by seafood.
Clinical features : Common symptoms include vomiting, diarrhoea and abdominal pain, with or without fever. Serious complications, such as dehydration and septicaemia leading to death may occur when appropriate treatment is delayed, but these are rare.

Causative agent : Clostridium perfringens (Bacteria)
Places where such agents are commonly found : Soil, plants and animal excrements.
Usual source of food poisoning by such agents : Cross-contaminated and inadequately cooked or stored meat and meat products (e.g. stewed dishes and gravy).
Clinical features : Common symptoms include vomiting, diarrhoea and abdominal pain, with or without fever. Serious complications, such as dehydration and septicaemia leading to death may occur when appropriate treatment is delayed, but these are rare.

Causative agent : Ciguatera fish poisoning (Biochemical toxin)
Places where such agents are commonly found : Marine coral reef fish
Usual source of food poisoning by such agents : Marine coral reef fish
Clinical features : Numbness in limbs, face, tongue or around the mouth, cold objects perceived as hot and vice versa, dizziness, palpitation and chest pain.

Causative agent : Tetrodotoxin poisoning (Biochemical toxin)
Usual source of food poisoning by such agents : Puffer fish and porcupine fish
Related information : Food Safety Focus (9th Issue, April 2007)

Causative agent : Pesticide (Chemical toxin)
Places where such agents are commonly found : Vegetables contaminated by pesticides
Usual source of food poisoning by such agents : Inadequately soaked or rinsed contaminated leafy vegetables
Clinical features : Dizziness, muscle weakness, numbness, tearing, salivation and palpitation. Severe poisoning may lead to blurred vision, tremor or fits and breathing difficulty.

Mode of transmission

Food poisoning is caused by the consumption of food containing or contaminated by the causative agent.

Incubation period

Incubation period varied from hours to days according to the causative agent.

Management

Seek prompt medical advice if you have symptoms of food poisoning. Fluid replacement is usually required. Advise sick food handlers to stay away from work till the illness is over.

Prevention

1.  Keep the premises and kitchen utensils clean. Dispose rubbish properly.
2.  Keep hands clean and fingernails trimmed.
3.  Wash hands properly with soap and water before eating or handling food, and after toilet or changing diapers.
4.  Drinking water should be from the mains and preferably boiled.
5.  Purchase fresh food from reliable sources. Do not patronize illegal hawkers.
6.  Avoid high risk food like shellfish, big coral reef fish, raw food or semi-cooked food.
7.  Wear clean washable aprons and caps during food preparation.
8.  Clean and wash food thoroughly.
9.  In preventing pesticide contaminated vegetable poisoning, the following points should be noted:

  • Remove outer leaves and stems of vegetables
  • Rinse the vegetables under running water several times
  • Immerse the vegetables in clean water for an hour (Soda flour may or may not be added);
  • Rinse the vegetables again
  • Alternatively, use boiling water to irrigate the vegetables for one minute and discard the used water

10.  Store perishable food in refrigerator, well covered.
11.  Handle and store raw and cooked food separately (upper compartment of the refrigerator for cooked food and lower compartment for raw food) to avoid cross contamination.
12.  Clean and defrost the refrigerator regularly and keep the temperature at or below 4oC.
13.  Cook food thoroughly.
14.  Do not handle cooked food with bare hands; wear gloves if necessary.
15.  Consume food as soon as it is done.
16.  If necessary, refrigerate cooked leftover food and consume as soon as possible. Reheat thoroughly before consuming. Discard any addled food items.
17.  In preventing ciguatera fish poisoning, the following points should be noted:

  • Avoid eating big coral reef fish; the bigger the fish, the higher the risk of ciguatera poisoning. Pay extra attention between February and May each year as the ciguatera toxin in the fish will be higher.
  • Eat only a small quantity at any one time. Do not consume together with alcohol and nuts, as symptoms of ciguatera poisoning will be exacerbated.
  • Do not eat the viscera especially liver and gonads of coral reef fish because the toxin tends to accumulate there.
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