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5 minutes to learn about Mycoplasma pneumoniae

Mycoplasma pneumoniae Mycoplasma is a microorganism between bacteria and virus. It is also called "atypical bacteria". The mycoplasma that can cause lung infection is Mycoplasma pneumoniae, which is more common in children and adolescents. Mild, mainly manifested as upper respiratory tract symptoms, such as sore throat, fever, cough, headache, etc. The pathological changes are mainly interstitial inflammation of the lungs, sometimes complicated by bronchopneumonia, which can occur in all seasons of the year, but more often in autumn and winter.

Mycoplasma pneumoniae antibody type One end of Mycoplasma pneumoniae has a special terminal structure, which enables Mycoplasma to adhere to the surface of respiratory mucosal epithelial cells and cause disease. Humans can produce specific IgM and IgG antibodies after infection with Mycoplasma pneumoniae. IgM antibodies appear early, generally appearing 1 week after infection, peaking in 3 to 4 weeks, and then gradually decreasing. Since the incubation period of Mycoplasma pneumoniae infection is 2 to 3 weeks, when the patient presents with symptoms and sees a doctor, the IgM antibody has reached a very high level, so the positive IgM antibody can be used as a diagnostic indicator for acute infection. However, if IgM antibodies are negative, Mycoplasma pneumoniae infection cannot be ruled out, and IgG antibodies should be detected. IgG appears later than IgM, and needs to be dynamically observed. If it is significantly increased, it indicates infection, and if it is significantly decreased, it indicates that it is in the late stage of infection. Therefore, when IgM antibody is negative and IgG is positive, double serum testing in acute phase and convalescent phase is required to provide valuable laboratory diagnosis basis for clinical practice.

Propagation mode

Mycoplasma pneumoniae is mainly transmitted through respiratory droplets, and the source of infection is patients and convalescent carriers. Healthy people are infected by inhaling the waste from the mouth and nose of patients when they cough and sneeze. The incubation period is 1 to 3 weeks, and it is contagious during the incubation period until the symptoms are relieved for several weeks.

Clinical manifestations after infection

The clinical manifestations of children infected with Mycoplasma pneumoniae are varied, mainly the manifestations of respiratory tract infection. The symptoms usually manifest as upper respiratory tract symptoms such as fever, sore throat, and fatigue at the beginning, and then develop to the lower respiratory tract. Severe irritating cough can cause pneumonia and difficulty breathing. In severe cases, complications outside the respiratory system such as myocarditis, encephalitis, and nephritis may even occur.

Methods to detect Mycoplasma pneumoniae

Detection methods for Mycoplasma pneumoniae include pathogen culture, polymerase chain reaction (PCR) and antibody serology experiments. Pathogen culture method is time-consuming and is not conducive to early diagnosis, so it is not widely carried out in clinical practice. The PCR method requires a special experimental environment and specific equipment, and is generally only carried out in large and medium-sized hospitals. Antibody serology experiments include ELISA, passive agglutination, colloidal gold and other methods, which can be diagnosed by detecting the specific antibody IgM antibody of Mycoplasma pneumoniae. Among them, the passive agglutination method and the colloidal gold method are simple and fast to operate, suitable for hospitals at all levels, and are currently widely used.

Mycoplasma pneumoniae IgM antibody positive

After the human body is infected with Mycoplasma pneumoniae, the serum Mycoplasma pneumoniae IgM antibody appears earlier, generally appearing in 1 week, reaching a peak in 3-4 weeks, and then gradually decreasing to disappear, and some patients can last for 12-16 weeks or even longer. IgG antibodies are produced later. Therefore, when a child presents with respiratory symptoms and sees a doctor, positive Mycoplasma pneumoniae IgM antibody can be used as a diagnostic indicator for acute infection. Since IgM antibodies can continue to exist in the body for a period of time after infection with Mycoplasma pneumoniae, when the disease recovers and the child has no clinical symptoms, many parents always think about rechecking Mycoplasma pneumoniae IgM antibodies to see if it has turned negative, but it is not necessary. . That is to say, the Mycoplasma pneumoniae IgM antibody is still positive at this time, which does not mean that the condition has not improved or that the Mycoplasma has been re-infected.

Mycoplasma pneumoniae IgM antibody Negative

Some children are clinically suspected of Mycoplasma pneumoniae infection, but the Mycoplasma pneumoniae IgM antibody test is negative. At this time, a comprehensive evaluation should be carried out in combination with the course of the disease and the age of the child, and Mycoplasma pneumoniae infection cannot be completely excluded. Because if the detection time is too early after infection with Mycoplasma pneumoniae, the serum has not yet produced Mycoplasma pneumoniae IgM antibody, and the test result may be negative. Infants and young children may have false negative test results due to their imperfect immune function and low ability to produce antibodies. In addition, limited by the detection method, there will also be a certain false negative rate.

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