Bacterial poisoning can arise from the intake of water or contaminated or poorly stored food. Toxins that pollute both water and food can originate from the soil - such as Clostridium Botulinum or the Clostridium Perfringens - or in animals, such as salmonella, brucella and other types of parasites. Ultimately, these bacteria can also come from humans, like Vibrio Colerae, Staphylococcus Aureus And Salmonella Tifi.
First of all it is good to specify the difference between food poisoning and food infections. The latter, in fact, are linked to the introduction into our organism of the bacterium present in the contaminated food, while in food poisoning the organism itself is not introduced so much, but rather its preformed toxin.
The times of manifestation of the toxic effects are very different between intoxication and infection. When the preformed toxin is introduced, the times of manifestation are very rapid, with the presence of nausea, hemorrhagic diarrhea, vomiting. If, on the other hand, the bacterium is introduced in its entirety, the onset times vary from a few hours to several days.
Among the main microorganisms involved in food poisoning, we remember the various types of salmonella. These bacteria contain an endotoxin that causes a characteristic symptomatology, gastroenteritis. Salmonella can be found in all meats, both white and red, in eggs, fish, molluscs and some types of vegetables.
The Clostridium Perfringens it produces an "enterotoxin, so its harmful effect is expressed in the intestine. This toxin is an enzyme called lecithinase, capable of breaking down lecithin (phospholipid) into isolecithin, which has a" haemolytic action. A "foodborne infection with Clostridium Perfringens it can be accused when you eat raw or undercooked meat or fish.
The Vibrio Colerae it produces an "enterotoxin that causes an" alteration of the osmotic balance in the cells of the intestinal wall, drawing water into the intestine. The consequence is a strong hemorrhagic diarrhea, which leads to a deep dehydration and even death of the contaminated person. In most cases it is the water that is polluted by Vibrio Colerae, so you can run into a "choleric infection through the consumption of shellfish, raw fruit and vegetables.
The Staphylococcus Aureus causes food poisoning thanks to an enterotoxin that causes gastrointestinal imbalances associated with fever.
The Clostridium Botulinum it forms easily in improperly stored foods, such as all jars of preserves and in oil that can be kept in the fridge for a certain number of days. Botulinum toxin is a neurotoxin and can lead to death due to a blockade of acetylcholine at the pre-synaptic level. The effect is a flaccid paralysis of the muscle tissues.
MECHANISMS OF ACTION OF BACTERIAL TOXINS
The mechanisms of action of bacterial toxins can be manifold. It should be remembered that bacterial toxins are substances of protein origin produced by microbial species. These toxins are released or not in the environment with the aim of penetrating and proliferating in the host organism.
The various mechanisms of action are mainly two. The first consists in the action of toxins on cell membranes and the second in the action of toxins on receptors.
THE TOXINS THAT GO TO ACT ON THE CELL MEMBRANES
These toxins cross the cell membrane by forming a channel. With the formation of this opening, the extracellular liquid can pour into the cell, causing swelling and lysis of the cell itself. Other toxins act on enzymes that modify the phospholipid structure of the membrane, creating a breach in the membrane itself. . Consequently, there will be an outflow of the cellular components and an excessive entry of extracellular fluid, once again causing the cell to die from lysis.
The Clostridium Perfringens and it Staphylococcus Aureus are the main bacteria that produce toxins with this mechanism of action Staphylococcus Aureus in part they act in a non-specific way and in part in a specific way, acting on some types of cells such as red blood cells and macrophages. It is important to remember that within the same bacterium there can be several toxins that act in different ways.
There are also toxins that act on the membrane lipids of nerve cells, called gangliosides, so they act specifically on the cells of the CNS.
THE TOXINS THAT ACT ON THE RECEPTORS
They are toxins that have a specific target on the cell (receptors). All these toxins can be classified into:
- SUPERANITGENE TOXIN;
To be recognized as an antigenic substance capable of activating the immune system, superantigenic toxins must bind to something else. A superantigenic toxin binds to the type 2 major histocompatibility complex, a cell membrane protein complex that it favors the recognition of the bacterial antigen by the B and T lymphocytes of the immune system. Therefore, the toxin alone is unable to activate the immune response, but must bind to the type 2 major histocompatibility complex and form the superantigen. Only by doing this can the toxin trigger an immune system response. An example of superantigenic toxins is given by the enterotoxins produced by staphylococci, which give rise to a form of intoxication characterized by erythema, hypotension, intestinal and neurological dysfunctions.
Endotoxins are not released by the bacterium, but are part of the structure of the bacterium itself. Endotoxins are usually the components of the outer membrane of Gram negative bacteria. A mild endotoxin intoxication is characterized by fever and hypotension, while in the case of large concentrations these toxins can even lead to death.
Both superantigenic toxins and endotoxins have the effect of uncontrolled activation of the immune system: they trigger the production of antibodies by B lymphocytes, trigger the production of cytokines by T lymphocytes, increase the production of prostaglandins (PG) and finally reactive oxygen species increase.
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