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Toxic reaction of Endotoxin

Gram-negative bacteria, (such as typhoid bacillus, dysentery bacillus, etc.), the general term for the toxic substances present in the bacteria. It is a component of the cell wall of a variety of Gram-negative bacteria. The toxin released by the lysis of the bacteria is also called “pyrogen”. The unit is Eu/ml. Its chemical components are phospholipid polysaccharide-protein complexes, and its toxic components are mainly lipid-like A. Endotoxin is located on the outermost layer of the cell wall, covering the mucopeptide of the cell wall. The toxic effects of endotoxins of various bacteria are relatively weak and roughly the same, which can cause fever, microcirculation disorders, endotoxin shock, and disseminated intravascular coagulation. Endotoxin is heat-resistant and stable, with weak antigenicity. It can stimulate the body to produce antibodies, but it has no neutralizing effect and forms an antitoxin. It cannot become a toxoid after treatment with formaldehyde.

Endotoxin is a component in the cell wall of Gram-negative bacteria called lipopolysaccharide. Lipopolysaccharide is toxic to the host. Endotoxin is released only when the bacteria die and dissolve or destroy the bacterial cells by artificial methods, so it is called endotoxin.

Endotoxin is not a protein, so it is very heat-resistant. Heating at a high temperature of 100°C for 1 hour will not be destroyed. Only heating at a temperature of 160°C for 2 to 4 hours, or heating and boiling with strong alkali, strong acid or strong oxidant for 30 minutes can destroy its biological activity. The difference with exotoxin is that endotoxin cannot be detoxicated by dilute formaldehyde solution to become toxoid; although endotoxin can be injected into the body to produce a certain amount of specific immune product (called antibody), this antibody counteracts the internal The toxicity of toxins is weak.

 

Toxic reaction

The endotoxin lipopolysaccharide molecule is composed of three parts: cell-specific polysaccharide, non-specific core polysaccharide and lipid A. Lipid A is the main toxic component of endotoxin. The structure of lipid A of different gram-negative bacteria is basically similar. Therefore, all infections caused by Gram-negative bacteria, although the bacterial species are different, the toxic effects caused by endotoxins are roughly the same. These toxic reactions mainly include:

 

Febrile reaction

The human body is extremely sensitive to bacterial endotoxins. A very small amount of endotoxin (1-5 ng/kg body weight) can cause body temperature to rise, and the fever reaction lasts for about 4 hours and then gradually subsides. During natural infections, gram-negative bacteria continue to grow and multiply, accompanied by successive deaths and release of endotoxin, so the fever will continue until the pathogenic bacteria in the body are eliminated. Endotoxin causes fever response is that endotoxin acts on macrophages and neutrophils in the body to produce interleukin 1, 6 and tumor necrosis factor alpha and other cytokines, these cytokines act on the host hypothalamus The body temperature regulation center, promotes the body temperature to rise and fever.

 

White blood cell response

After bacterial endotoxin enters the host, the number of neutrophils, which account for 60-70% of the total number of white blood cells in the bloodstream, decreases rapidly. This is because the cells move and adhere to the capillaries of the tissue. However, after 1-2 hours, the neutrophil-releasing factor induced by endotoxin stimulates the bone marrow to release neutrophils into the bloodstream, causing the number to increase significantly, and some immature neutrophils are released. The exception is Salmonella typhi, which is a gram-negative bacterium, whose endotoxin keeps the total number of white blood cells always in a reduced state. Since the total number of white blood cells in the bloodstream of most patients infected by gram-negative bacteria will increase, doctors often need to test the patient’s blood to determine the total number of white blood cells in order to make a preliminary distinction between bacterial infections and viral infections before diagnosis. Determination and classification count. In patients infected with the virus, the total number of white blood cells and the percentage of neutrophils are basically within the normal range.

 

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