What is mycoplasma?

Mycoplasma found in 1898, also known as mycoplasma hominis, is a simple prokaryotic organism. Its size is between bacteria and viruses. \x0d\ is relatively simple in structure, mostly spherical, with no cell wall and only three cell membranes, so it has great variability. Mycoplasma can be inoculated on special culture medium to grow, and this method can be used for clinical diagnosis. Ureaplasma urealyticum and mycoplasma hominis are the main pathogens of urogenital tract infection. About 20-30% of patients with nongonococcal urethritis are caused by the above two mycoplasma, which is the second largest pathogen of nongonococcal urethritis and cervicitis. The infection rate of ureaplasma urealyticum and mycoplasma hominis in adult urogenital tract is mainly related to sexual activity, that is, to the number of sexual intercourse and the number of sexual partners, and has nothing to do with gender. According to statistics, the infection rate of female mycoplasma is high, which shows that female genital tract is more likely to grow mycoplasma than male genital tract. In addition, the infection rate of ureaplasma urealyticum is higher than that of mycoplasma hominis. \x0d\ Abbreviation: \x0d\ pplo \x0d\ Chinese full name: \x0d\ Mycoplasma \x0d\ English full name: \ x0d \ pleuropneumonia-like tissue \ x0d \ Chinese meaning (China tissue culture contaminated pleuropneumonia-like bacteria \ x0d \ English explanation): \ x0d \. Among the mycoplasma causing mycoplasma, mycoplasma pneumoniae causes pneumonia, and mycoplasma hominis, ureaplasma urealyticum and mycoplasma genitalium are mycoplasma pneumonia, also known as primary atypical pneumonia, which can occur all year round, especially in winter, and may have a small epidemic. Mycoplasma pneumonia is a common pneumonia in preschool children and adolescents. Mycoplasma pneumonia is mainly transmitted by droplets, with a long incubation period of 2 ~ 3 weeks. Although mycoplasma pneumonia has a long course of disease, serious lung lesions and slow absorption of inflammation, most of them have a good prognosis and few complications. Genital mycoplasma infection is a new sexually transmitted disease in recent years. Adults are mainly transmitted through sexual contact, while newborns are infected through their mothers' reproductive tract during childbirth. The infection site of adult male is in urethral mucosa, and that of female is in cervix. Newborns mainly cause conjunctivitis and pneumonia. Ureaplasma urealyticum is a prokaryotic microorganism, rod-shaped, with a size of 125-250 nm and a molecular weight of 4.5* 108. It is highly polymorphic and has no hard cell wall. It can proliferate in sterile culture and produce urease to decompose urea. Specific antibodies can inhibit its growth, because it lacks hard cell membrane, is resistant to penicillin, has affinity for cell membrane, and needs steroids for growth and reproduction. Ureaplasma urealyticum can not be found in the reproductive tract of infants or women who have no sexual contact. The more chaotic the sexual life, the higher the positive rate of this mycoplasma. McDonald 1982 reported that among 587 patients with acute urethritis, 209 patients (36%) were separated from the middle urine. Mycoplasma has weak resistance to external environment and can be killed at 45℃ 15min. Mycoplasma can only attach to the receptors on the surface of epithelial cells of respiratory tract or urogenital tract, and does not enter tissues and blood. The causes of cell damage caused by mycoplasma are as follows: Mycoplasma adhering to the surface of host cells absorbs nutrients from cells and obtains lipids such as cholesterol from cell membranes, causing cell damage; Toxic substances produced by mycoplasma metabolism, such as Mycoplasma neurolyticum, can produce neurotoxins and cause cell membrane damage; Ureaplasma contains urease, which can hydrolyze urea to produce a large amount of ammonia, which is toxic to cells. Mycoplasma can not only adhere to the surface of cells and macrophages, but also adhere to the surface of sperm, thus preventing sperm from moving. Neuraminidase-like substances produced by mycoplasma can interfere with the combination of sperm and eggs. This is one of the causes of infertility caused by mycoplasma infection. \x0d\ In animal experiments, it is found that peritoneal macrophages in mice can kill mycoplasma, but neutrophils have little effect. In vitro, IgG 1 and IgG2 antibodies have a conditioning effect. It can strengthen the killing effect of macrophages on mycoplasma. \x0d\ Infection hazards \x0d\ Urethritis symptoms \x0d\ When mycoplasma is infected through urethra, the patient's friends may have urethritis symptoms, and chronic prostatitis caused by mycoplasma and chlamydia may be secondary. Women can see the cervix and vestibular glands, causing urethritis, cervicitis and vestibular adenitis. \x0d\ leads to male infertility \x0d\ cannot be treated in time because of mycoplasma infection. However, this microorganism continues to infect seminal vesicles and testicles, affecting the quality of sperm and semen, resulting in infertility. The pathological changes of male sperm caused by Ureaplasma urealyticum infection lead to male infertility. \x0d\ Interfere with sperm movement \x0d\ However, after being infected by mycoplasma, the delay of onset will affect the speed and frequency of sperm movement to some extent. \x0d\ Decline of male sexual function \x0d\ Due to the damage of pathogenic microorganisms to reproductive organs and sexual nerve reaction terminals, sexual nerves are insensitive to effective stimulation, sexual organs are in refractory period for a long time, and sexual desire and reaction are weakened, which may lead to impotence over time. \x0d\3 Main features \x0d\ morphological structure \x0d\ Mycoplasma is 0.2 ~ 0.3 um in size, which can pass through bacterial filters, often bringing pollution troubles to cell culture. The colony is small (diameter 0. 1~ 1.0mm) and has a unique "fried egg" shape on the surface of solid medium. It has no cell wall, can not maintain a fixed shape and is polymorphic, sensitive to osmotic pressure and insensitive to antibiotics that inhibit cell wall synthesis. Gram staining is not easy to dye, so Giemsa staining is often used to dye it lavender. The content of cholesterol in cell membrane is relatively high, accounting for about 36%, which plays a certain role in maintaining the integrity of cell membrane. Cell membrane contains sterols, which are tougher than other prokaryotes. Any substance that can act on cholesterol (such as amphotericin B, saponin, etc. ) can cause the destruction of mycoplasma membrane and make mycoplasma die. \x0d\ Mycoplasma genome is a circular double-stranded DNA with very small molecular weight (only one fifth of that of Escherichia coli), and its synthesis and metabolism are very limited. \x0d\ One end of Mycoplasma pneumoniae has a special terminal structure, which can make Mycoplasma adhere to the surface of respiratory mucosa epithelial cells, which is related to pathogenicity. \x0d\ Biochemical reaction and typing \x0d\ Mycoplasma can generally decompose glucose but can't utilize arginine, and those that can utilize arginine can't decompose glucose, so mycoplasma can be divided into two categories. Ureaplasma urealyticum can not use glucose or arginine, but can use urea as energy source. \x0d\ All kinds of mycoplasma have specific surface antigen structures and few cross reactions, so they are type-specific. Growth inhibition test (GIT) and metabolic inhibition test (MIT) were used. We can identify and classify dendritic antigens. \x0d\ It is widely distributed in nature, with more than 80 species. Mycoplasma related to human beings include Mycoplasma pneumoniae (Mp), Mycoplasma hominis (MH), Ureaplasma urealyticum (UU decomposes Ureaplasma urealyticum) and Mycoplasma genitalium (MG). \x0d\ Mycoplasma pneumoniae causes pneumonia. At present, seven kinds of mycoplasma have been isolated from human urogenital tract, among which Ureaplasma urealyticum has a high isolation rate, followed by Mycoplasma hominis, which is related to urogenital diseases. Mycoplasma hominis (MH), Ureaplasma urealyticum (UU) and Mycoplasma genitalium (MG) can all cause urogenital tract infections. \x0d\ Broadly speaking, L-type bacteria are a kind of strains with cell wall deletion, which spontaneously mutate or become under the action of antibiotics and lysozyme, and many characteristics are similar to mycoplasma; Strictly speaking, L-form bacteria should refer to those strains with stable cell wall defects formed by spontaneous mutation in laboratory or host. The wall-lacking cells formed by artificial wall removal are called protoplasts (completely eliminated) and spheroids (partially eliminated) respectively. \x0d\ Difference between Mycoplasma and L-type bacteria \x0d\ Mycoplasma \x0d\ Most of the cholesterol needed for growth exists widely in nature \x0d\ and has nothing to do with bacterial inheritance. Under any conditions, it cannot be turned into bacteria \x0d\ L-type bacteria with a small colony of 0. 1 ~ 0.3 mm \x0d\ x0. After removing the inducing factors, the original bacteria \x0d\ colony is slightly larger, and 0.5 ~ 1.0 mm \x0d\ mycoplasma pneumoniae \x0d\ mycoplasma pneumoniae (M. pneumoniae) is the pathogen of mycoplasma pneumonia. The pathological changes of mycoplasma pneumonia are mainly interstitial pneumonia, sometimes complicated with bronchopneumonia, which is called primary atypical pneumonia. It is mainly transmitted by droplets, and the incubation period is 2 ~ 3 weeks, and the incidence rate of adolescents is the highest. Clinical symptoms are mild, even no symptoms at all. If there is, it is only common respiratory symptoms, such as headache, sore throat, fever and cough, but there are also some death reports. It can happen all year round, but it mostly happens in autumn and winter. \x0d\ The pathogenicity of Mycoplasma pneumoniae first attaches to the surface of the host cell through its apical structure, then extends out of microtubules and inserts them into the cell to absorb nutrients and destroy the cell membrane, and then releases metabolites such as nuclease and hydrogen peroxide to cause cell lysis, epithelial cell swelling and necrosis. Antibodies induced by organisms may also participate in the above pathological damage. SlgA secreted by respiratory tract has a certain defensive effect on reinfection, but it is not firm enough. \x0d\ The diagnostic methods of Mycoplasma pneumoniae mainly rely on isolation, culture and serological tests. Specimens can be taken from sputum or throat samples of suspected patients and inoculated in agar medium containing serum or yeast extract. After 5 ~ 10 days, observe whether there are round roof-shaped colonies with a diameter of 30 ~ 100 um. After many passages, it can become a typical "poached egg"-like colony, which can adsorb many kinds of animal red blood cells, tracheal epithelial cells, HeLa cells and so on. And this adsorption can be inhibited by specific antibodies. After preliminary identification by morphology, hemolysis and biochemical reaction, the isolated mycoplasma needs further growth inhibition test and metabolic inhibition test with specific antiserum. Complement fixation test with patient serum and mycoplasma lipid antigen has diagnostic value, and the titer in recovery period is more than 4 times higher than that in acute period. Indirect immunofluorescence test and indirect hemagglutination ELISA can also be used to detect samples. In addition, the serum of patients with 1/3 ~ 3/4 can react nonspecific with human O-type red blood cells at 4℃ (called "agglutination test"), which disappears at 37℃ and reaches its peak one week after illness. This method is simple and helpful for diagnosis. \x0d\ Resistance \x0d\ Mycoplasma has similar resistance to heat as bacteria. Sensitive to environmental osmotic pressure, sudden changes in osmotic pressure can cause cell rupture. It is more sensitive to heavy metal salts, carbolic acid, lysol and some surfactants than bacteria, but more tolerant to thallium acetate, crystal violet and antimonite than bacteria. It is not sensitive to antibiotics that affect cell wall synthesis, such as penicillin, but it contains PHMB bactericidal components to antibiotics that act on mycoplasma nucleosome, such as Jiao Yanjieyin lotion, erythromycin, tetracycline, streptomycin and chloramphenicol, which can inhibit or affect the synthesis of protein and kill mycoplasma. \x0d\ Pathogenicity and immunity \x0d\ Mycoplasma does not invade body tissues and blood, but causes cell damage through different mechanisms after epithelial cells of respiratory tract or urogenital tract adhere and settle down, such as obtaining lipid and cholesterol on cell membrane to cause membrane damage and releasing neurotoxin, phosphatase and hydrogen peroxide. \x0d\ Macrophages, lgG and lgM have certain killing effects on mycoplasma. SlgA antibody produced by respiratory mucosa has been proved to have the effect of preventing mycoplasma adsorption. In children, sensitized lymphocytes can enhance the body's resistance to mycoplasma pneumoniae.