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Food Poisoning
CAUSATIVE AGENTS OF FOOD-POISONING
POST FOOD POISONING SYNDROME (PFPS)
BACTERIAL PRODUCTS/TOXINS
CAUSATIVE AGENTS OF FOOD-POISONING
The most commonly recognised foodborne infections are those caused by the bacteria Campylobacter, Salmonella, and E. coli O157:H7, and by some caliciviruses, also known as the Norwalk and Norwalk-like viruses.
Campylobacter is a bacterial pathogen that causes fever, diarrhoea, and abdominal cramps. It is the most commonly identified bacterial cause of diarrhoeal illness in the world. These bacteria live in the intestines of healthy birds, and most raw poultry meat has Campylobacter on it. Eating undercooked chicken, or other food that has been contaminated with juices dripping from raw chicken is the most frequent source of this infection.
Salmonella is also a bacterium that is widespread in the intestines of birds, reptiles and mammals. It can spread to humans via a variety of different foods of animal origin. The illness it causes, salmonellosis, typically includes fever, diarrhoea and abdominal cramps. In persons with poor underlying health or weakened immune systems, it can invade the bloodstream and cause life-threatening infections.
E. coli O157:H7 is a bacterial pathogen that has a reservoir in cattle and other similar animals. Human illness typically follows consumption of food or water that has been contaminated with microscopic amounts of cow feces. The illness it causes is often a severe and bloody diarrhoea and painful abdominal cramps, without much fever. In 3% to 5% of cases, a complication called haemolytic uraemic syndrome (HUS) can occur several weeks after the initial symptoms. This severe complication includes temporary anaemia, profuse bleeding, and kidney failure.
Calicivirus, or Norwalk-like virus is an extremely common cause of foodborne illness, though it is rarely diagnosed, because the laboratory test is not widely available. It causes an acute gastrointestinal illness, usually with more vomiting than diarrhoea, that resolves within two days. Unlike many foodborne pathogens that have animal reservoirs, it is believed that Norwalk-like viruses spread primarily from one infected person to another. Infected kitchen workers can contaminate a salad or sandwich as they prepare it, if they have the virus on their hands. Infected fishermen have contaminated oysters as they harvested them.
Some common diseases are occasionally foodborne, even though they are usually transmitted by other routes. These include infections caused by Shigella, hepatitis A, and the parasites Giardia lamblia and Cryptosporidia. Even strep throats have been transmitted occasionally through food.
In addition to disease caused by direct infection, some foodborne diseases are caused by the presence of a toxin in the food that was produced by a microbe in the food. For example, the bacterium Staphylococcus aureus can grow in some foods and produce a toxin that causes intense vomiting. The rare but deadly disease botulism occurs when the bacterium Clostridium botulinum grows and produces a powerful paralytic toxin in foods. These toxins can produce illness even if the microbes that produced them are no longer there.
Other toxins and poisonous chemicals can cause foodborne illness. People can become ill if a pesticide is inadvertently added to a food, or if naturally poisonous substances are used to prepare a meal. Every year, people become ill after mistaking poisonous mushrooms for safe species, or after eating poisonous reef fishes.
POST FOOD POISONING SYNDROME (PFPS)
Food poisonings always cause an imbalance of the "normal" gut flora and patients might suffer from dysbacteriosis/dysbiosis for quite a while. PFPS is a new field which might help to explain some types of IBS-related symptoms.
More and more autoimmune disorders are linked to bacteria and/or bacterial products in foods.
(more to come)
Campylobacter jejuni
Photo courtesy CDC
BACTERIAL PRODUCTS/TOXINS
- Bacillus cereus produces endotoxin about which there is little known. Bacillus cereus produces hemolysin and lecithinase which is not toxic and is a phospholypase. But the spores of these bacteria can cause mild to severe food-poinsoning (sometimes called the "China-Restaurant Syndrome", because sporulation takes place in cold/reheated rice.
- Campylobacter jejuni produces endo- and enterotoxin.
- Clostridium botulinum produces exotoxins from type A, B, C, D, E and F. They are the strongest toxins which are known and act as neurotoxins. They inhibit the excretion of acetylcholine avoiding thus the transmission of signals from the nerve to the muscle causing paralysis comparable to the effect of curare, the poison of South American Indians.
The endotoxins which are thermo unstable are formed in canned food with a pH higher than 4.5 and about 6 month of storage. This toxin is destroyed when food is cooked before serving.
- Clostridium perfringens produces an enterotoxin formed in bad refrigerated precooked food.
- Escherichia coli produces an enterotoxin under bad hygienic conditions.
- Listeria monocytogenes produces listeriolysine.
- Salmonella enteritides produces a heat unstable exotoxin mainly in ground meat, in eggs, in poultry, in milk powder, in chocolate and fine salads.
- Salmonella typhimurium produces a heat unstable exotoxin.
- Shigella dysenteriae and Shigella sonnei produce endotoxin or heat unstable exotoxins.
- Shigella dysenteriae, Shigella sonnei and Staphylococcus aureus, produce thermostable toxins. The toxins produced by Staphylococcus aureus can be classified serologically as toxin A, B, C1, C2, D, E and F. About 19% of Staphylococcus aureus are toxin producing strains.
The toxin A and B are resistant to very high temperatures and may resist even to 20 minutes at 121,1 C. Often there are no sensory changes in food with staphylocoxin.
In the production of industrialised food all efforts should be made to avoid a contamination of food with Staphylococcus aureus, paying great attention to avoid handling of food by person with suppurative focuses.
Streptococcus faecalis, produces thermostable toxins
Vibrio cholerae produce enterotoxin.
Vibrio parahaemolyticus produces exotoxin.
Yersinia enterocolytica produces enterotoxin. |
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