Diseases caused by bacteria

Bacteria ( tiny one -celled organisms) can cause two types of food poisoning - infective food poisoning and toxic food poisoning:

• Infective food poisoning occurs as a result of eating live bacteria that is in the food. The best way to prevent this type of food poisoning is to prevent the growth of the micro-organisms. Examples of bacteria that cause infective food poisoning are Salmonella, Listeria and Escherichia coli.


• In contrast, toxic food poisoning results from toxins that are produced by some bacteria and it is these toxins that cause illness. In general , the toxins cannot be removed or inactivated by cooking. The main food poisoning bacteria that produce toxins are Staphylococcus aureus, Clostridium perfringens and some types of Escherichia coli.

SALMONELLOSIS
Bacteria: Salmonella
Source: Spread when contaminated food (meat, poultry, eggs or milk) is eaten raw or undercooked. Also, when cooked food comes in contact with contaminated raw food, or when an infected person prepares food.
Symptoms: Onset 6–48 hours after eating; nausea, fever, headache, abdominal cramps, diarrhoea and vomiting lasting 2–7 days. Can be fatal to infants and the elderly.
Prevention: Separate raw foods from cooked foods. Thoroughly cook meat, poultry and eggs. Do not leave food for over two hours at room temperature. Refrigerate food at below 5 degree C.

STAPHYLOCOCCAL FOOD POISONING
Bacteria: Staphylococcus aureus
Source: Carried by people on skin in boils, pimples and throat infections; spread when carriers handle food. Staph bacteria produce toxins (poisons) at warm temperatures. Found in meat, poultry, salads, dressings, gravies, cream sauces, cheese, eggs, custards and cream –filled desserts.
Symptoms: Onset 1–8 hours after eating; vomiting, diarrhoea, nausea and abdominal cramps lasting 1–2 days. Rarely fatal.
Prevention: Cooking will not destroy staph poison, so practise good personal hygiene and sanitary food handling. Do not leave perishable food unrefrigerated for over two hours. For quick cooling, place hot food in small containers no more than two centimetres deep, cover when cool and refrigerate.

BOTULISM
Bacteria: Clostridium botulinum
Source: Most common in low-acid foods canned improperly at home. The presence of these bacteria or their poisons is sometimes signalled by clear liquids turning milky, cracked jars, loose or dented lids, swollen or dented cans, or an ‘off’ odour. Found in meat and fish.
Symptoms: Onset 4–72 hours after eating; nervous system disturbances such as double vision, droopy eyelids, trouble speaking, swallowing or breathing. Untreated botulism can be fatal.
Prevention: Carefully examine canned goods and do not use any that show danger signs. Also, cook and reheat foods thoroughly, keep cooked foods hot (above 60 degree C) and cold (below 5 degree C), and divide larger portions of cooked food into smaller portions for serving and cooling.

PERFRINGENS FOOD POISONING
Bacteria: Clostridium perfringens
Source: Called the ‘buffet germ’, it grows rapidly in large portions of food that cool slowly. It grows in warming dishes, which may not keep food sufficiently hot, and in the refrigerator if food is stored in portions that are too large to cool quickly. Found in meat and poultry.
Symptoms: Onset 8–12 hours after eating; diarrhoea, abdominal cramps, headache, chills.
Prevention: Keep food hot or cold. Reheat food carefully, especially soups and casseroles.

CAMPYLOBACTERIOSIS
Bacteria: Campylobacter jejuni
Source: Found in raw milk, eggs, poultry, raw beef, cake icing and water.
Symptoms: Onset 2–10 days after eating; severe diarrhoea, cramps, fever and headache.

Prevention: Pasteurise milk, cook foods properly.

LISTERIOSIS
Bacteria: Listeria monocytogenes
Source: Common in food-processing environments and digestive tracts of humans. Found in untreated water and milk, dairy products, raw meat and seafood.
Symptoms: Onset 2-30 days after eating; fever, flu-like symptoms. Infants may vomit, have trouble breathing; pregnant women, in particular, are at risk.
Prevention: Avoid foods that are not pasteurised.

SHIGELLOSIS
Bacteria: Shigella
Source: Poor sanitary habits spread by touching moist foods. Bacteria multiply at room temperature. Found in poultry, salads and foods that require mixing but not heating.
Symptoms: Onset 1-7 days after eating; abdominal pain, fever and vomiting.
Prevention: Good personal hygiene; refrigerate perishable foods.

BACILLUS CEREUS FOOD POISONING
Bacteria: Bacillus cereus
Source: Found in cooked rice that was not refrigerated and then consumed; pasta, potatoes, meat, milk.
Symptoms: Diarrhoea and vomiting.
Prevention: Refrigerate perishable foods.

HAEMORRHAGIC COLITIS
Bacteria: Escherichia coli
Source: Drinking water contaminated by sewage transmitted to raw food.
Symptoms: Onset 3 -4 days after eating; severe abdominal cramps, diarrhoea, vomiting and fever.
Prevention: Do not consume untreated water; thoroughly cook food.

Questions:

1. Explain the difference between infective food poisoning and toxic food poisoning.

2. Which food poisoning is more dangerous and why? Support your answer with examples.