Into Staphylococcus aureus
Staphylococcus aureus is abbreviated as Staphylococcus aureus. It is a kind of spherical bacteria. Under the microscope, they gather in clusters, arranged in clusters of grapes and are golden yellow in a good nutrient environment. They are a kind of gram-positive bacteria, and are very “rough and thick”, aerobic or facultative anaerobic, low nutritional requirements, high salt tolerance, and can survive for several weeks even in a dry environment, regardless of whether there is oxygen or not. Existence, they can all grow. They are very common, whether in the air, water, dust, or on your skin or pores, there are Staphylococcus aureus.
Their favorite temperature is 37 ℃, and humans and animals are their good homes. In a healthy human body, the nose, throat and hands are the most suitable breeding grounds for their growth. The wound is also prone to a large number of S. aureus bacteria, and even the milk of cows suffering from mastitis may contain S. aureus.
The US Centers for Disease Control report shows that infections caused by Staphylococcus aureus occupy the second place in bacterial infections, second only to E. coli. Staphylococcus aureus enterotoxin is a worldwide health problem. Food poisoning caused by Staphylococcus aureus enterotoxin in the United States accounts for 33% of the total bacterial food poisoning; Canada has more, accounting for 45%; it is caused by Staphylococcus aureus in China Food poisoning incidents also occur from time to time.
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Staphylococcus aureus, known as the “super bacteria”, possesses amazing mutation ability and transmission ability. In the constant game and evolution with antibiotics, it has acquired the ability to resist a variety of antibacterial drugs.
Violent Staphylococcus aureus
In 1928, when Fleming was cultivating Staphylococcus aureus, he accidentally discovered that there were a transparent lysate in a petri dish contaminated with mold, indicating that these dots of green-green mold could secrete and kill Substance of Staphylococcus aureus. Then after ten years of hard work, this high-purity penicillin that can kill Staphylococcus aureus finally came out.
was beaten Staphylococcus aureus certainly will not stand still, antibiotics for humans it is fresh, and the bacteria was involved in this form of chemical warfare nearly a thousand years. The antibiotics purified by humans have accelerated the pace of their evolution. Methicillin-resistant Staphylococcus aureus (MRSA) was the first name to mainly define antibiotic-resistant Staphylococcus aureus strains. Methicillin came out in 1956, and only two years later, the first MRSA strain was discovered in the hospital. It can produce β-lactamase, which means that it can hydrolyze the lactam ring of penicillin and inactivate it. In some cases, the protein targeted by penicillin of Staphylococcus aureus has changed, which makes MRSA resistant to almost all β-lactam antibiotics.
In response to the emergence and spread of MRSA, the US Food and Drug Administration quickly approved the use of vancomycin in 1958 and became the drug of choice for MRSA infections. Unfortunately, a vancomycin-resistant Staphylococcus aureus was discovered in Japan in 1997 and was named “Mu50”. Staphylococcus aureus gave us another beautiful counterattack.
Weapon of Staphylococcus aureus
Once our body has an uninvited guest from outside, the immune system will sound the alarm and rush into battle. However, these witty enemies have a set of their own secret weapons, which interfere with the “enemy” to escape safely. When they invade the body, they first face the body’s first line of defense-neutrophils, which inhibit the activation of complement and the chemotaxis of neutrophils through various proteins such as chemotactic inhibitors. It is equivalent to that before the white blood cell army reaches the battlefield, they have already cut off the passage early, thus hindering the migration and adhesion of white blood cells to the battlefield.
Of course, even if the white blood cells that waded through the mountains and water successfully reached the battlefield, it didn’t matter, they could also secrete a powerful weapon—PVL, to compete with the white blood cells. PVL is an extracellular toxin composed of two types of proteins. These two proteins can pair with each other to form a ring structure polymer, which is then inserted into the target cell membrane to form a pore with a diameter of about 2 mm, which can selectively allow divalent The passage of cations, such as calcium ions and magnesium ions, accelerates the necrosis and apoptosis of white blood cells.
We know that the human body’s immune tissue is very witty. Once our body has been an uninvited guest, B cells with amazing memory will remember it firmly. When the enemy invades again, they will immediately activate face recognition and notify the lethal T Cell, annihilate the enemy in one fell swoop. However, Staphylococcus aureus has a unique mask and interference weapon protein A, which is a cell wall anchoring protein, which can perfectly adapt to antibody immunoglobulins, thereby paralyzing the face recognition system. These small memory markers Without any effect, the body’s phagocytosis will not be able to deal with these uninvited guests.
After evading the hunt, these Staphylococcus aureus bacteria will multiply by themselves while doing bad things. They secrete a protein called enterotoxin, which can cause food poisoning and allergic diseases. This protein is not only easily soluble in water and salt solution, but also can survive for 30 minutes at 100 ℃ or not be inactivated in the presence of pepsin. A very small dose of enterotoxin enters the gastrointestinal tract with contaminated food, but is not digested by pepsin, but is inhaled into the blood system, stimulating the central nervous system and causing vomiting. At the same time, enterotoxins can also stimulate lymphocytes to release interleukin-2 and interferon, inhibit humoral and cellular immunity, and they can multiply at this time.
Not only that, when Staphylococcus aureus invades the human body, they will produce plasma coagulase, which can activate thrombin fibrinogen to convert into fibrin, thereby coagulating blood containing anticoagulants and hindering the phagocytosis of phagocytes. This coagulation Enzymes are also related to staphylococci’s tendency to form local infections.
In addition, an exotoxin called hemolysin is not to be underestimated. They are divided into four types, which can damage platelets, destroy lysosomes, and cause body ischemia and necrosis. The heat-resistant nuclease, like enterotoxin, can withstand high temperature and will not be inactivated at 100 ℃ for 15 minutes. This enzyme can use the nucleic acid released by the tissues or leukocytes at the site of infection of Staphylococcus aureus during apoptosis and disintegration, and quickly decompose and transform them into nutrients they need. This substance is also often used in tests to determine whether food is contaminated with Staphylococcus aureus.
These witty coping styles are really interlinked. In fact, in most cases, Staphylococcus aureus colonizes our skin surface and nasal cavity in a co-existing state, and does not cause infection. But this group of eye-catching “enemies” has been hiding quietly by our side, waiting for opportunities. When the soft tissue is wounded, the original balance is broken. Staphylococcus aureus will not only colonize the wound surface, but also destroy tissue cells, triggering a protracted battle by fighting the body’s immune system, causing the wound to remain unhealed for a long time.
At present, the treatment of MRSA infection is still a very difficult problem in clinical practice. Fighting against superbugs requires not only the unremitting efforts of medical workers, but also the improvement of scientific literacy of citizens and the rational use of antibiotics. In this way, we can fight the super bacteria more smoothly.