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Mycoplasma pneumonia for adults

Mycoplasma infections diseases (MID)

It is the causative agent of infectious diseases that develop with "cold" symptoms, and is said to be the third most common in pneumonia and the first in acute bronchitis. In particular, pneumonia is the third leading cause of death in Japan and is the second most serious social problem after lifestyle-related diseases.

With the emergence of many resistant bacteria to antibiotics that have been effective in the past, it is becoming more and more important to reliably diagnose and treat them at an early stage. Since the isolation of macrolide antibiotic-resistant strains by Japanese researchers in 2000, the resistance rate has continued to rise. The number is increasing worldwide.

In 2011, an increase in the number of cases was reported from around June, and the highest number of infected people in the past 10 years has been reported. Factors contributing to the increase in the number of reports include the spread of rapid diagnostic kits, the increase in severe cases requiring hospitalization at the core fixed-point hospitals that are the subject of reports, and the resistance of the causative bacteria.

In addition, mycoplasma infections are characterized by 25% of infected humans being responsible for non-pulmonary diseases, such as dermatitis, nephritis, arthritis, and neurological symptoms such as meningitis and encephalitis. It can be. The course varies, from symptoms only in the acute phase to intractable diseases (asthma, rheumatic diseases, collagen diseases, neurological diseases).

It is often difficult to identify the cause because it presents a wide range of pathological features, including chronic inflammatory diseases. Clinical research field of intractable disease overcoming research project In 130 diseases, which are the targets of research, many diseases are suspected to be related to mycoplasma infection.

Therefore, it is very important to detect and diagnose mycoplasma infection, which is associated with chronic and intractable diseases, accurately and early, and to treat patients who are indicated for effective antibiotic therapy. It becomes.

Pathogenic mycoplasma

Mycoplasma is a bacterium that lacks a cell wall and exhibits various morphologies from spherical (125 to 250 nm) to fibrous (150 μm), and is the smallest bacterium that can self-proliferate extracellularly. Its growth requires cholesterol long chain fatty acids. Unlike viruses, it is the smallest pathogenic microorganism that can grow in artificial cell-free media.

Pathogens multiply extracellularly on the mucosal surface. As a result of proliferation, it destroys the airway mucosal epithelium such as the trachea, bronchi, bronchioles, and alveoli. In particular, the ciliated epithelium of the bronchi and bronchioles is significantly destroyed, and mucosal detachment and ulcer formation are observed. It may become severe due to a delay in definitive diagnosis, and adults are at high risk of becoming severe, and when it becomes severe, it may cause pleural effusion and respiratory failure.

Unlike ordinary bacteria, it does not have a cell wall and has a three-layer limit membrane, and antibiotics such as penicillin and cephem are ineffective, and macrolide and tetracycline antibiotics are said to be effective.

Mycoplasma attaches to tracheal fibroepithelial cells and proliferates, destroying the lower respiratory tract mucosal epithelium. Unlike ordinary bacteria, it does not have a cell wall and has a three-layer limit membrane, and antibiotics such as penicillin and cephem are ineffective, and macrolide and tetracycline antibiotics are effective.

Mycoplasma pneumonia occurs frequently in children and young adults. It also infects infants, but it rarely causes pneumonia and often ends with a cold or upper respiratory tract inflammation. Pneumonia symptoms appear when you are over 5 years old. Asymptomatic colonization continues after infection. Immunity does not last long after infection. Therefore, there is an increased risk of reinfection.

The infectivity is strong, and mycoplasma becomes droplets in the respiratory tract secretions of patients with mycoplasma pneumonia due to coughing, causing transairway infection. Since it is transmitted from person to person at a distance of about 1 to 2 m, the epidemic is seen in a narrow area such as schools and workplaces.

The pathogen is excreted in the airway mucus (sputum) from 2 to 8 days before the onset, the maximum at the onset of clinical symptoms, high level excretion lasts for about 1 week, and gradually decreases for 4 to 6 weeks or more. Emissions will continue. In addition, the season when pneumonia is prevalent is mainly from autumn to winter.

It is designated as a Class 5 infectious disease in the "Act on Prevention of Infectious Diseases and Medical Care for Patients with Infectious Diseases". In addition to pulmonary respiratory symptoms, there are systemic symptoms such as rash, myalgia, arthralgia, and meningitis. In addition, although rare, the transition to asthma, neurological disorders, and rheumatoid arthritis symptoms is known.

Clinical research field of intractable disease overcoming research project Of the 130 diseases targeted, many of them are suspected to be associated with mycoplasma infection. Epidemiological investigation of mycoplasma infection is extremely important because epidemics are seen in a narrow area such as schools and workplaces because droplets are transmitted from person to person at a distance of about 1 to 2 m.

Mycoplasma pneumonia (atypical pneumonia / atypical pneumonia)

Initial symptoms include cold syndrome-like symptoms such as fever, tiredness, headache, sore throat, gastrointestinal symptoms, cough, and rash. Symptoms vary greatly from person to person, and cough is a dry cough at the beginning of onset, but the cough becomes stronger over time and continues for about a month after the fever disappears. In older children and adolescents, a moist cough may occur in the later stages.

Complications include otitis media, arthritis, aseptic meningitis, encephalitis, hepatitis, pancreatitis, myocarditis, hemolytic anemia, Guillain-Barré syndrome, and Stevens-Johnson syndrome.

[Incubation period]

The incubation period is about 2 to 3 weeks. The incubation period is the period from the invasion of mycoplasma into the body to the appearance of symptoms. Symptoms do not appear immediately after contact with a person with mycoplasma infection, but after a few weeks.


The typical course is that the patient develops fever, coughs one or two days later, and then gradually intensifies. As for the symptoms of mycoplasma pneumonia, the initial symptoms are often the same as those of a common cold, and sore throat, general malaise, myalgia, and fever are the most common. After that, a stubborn cough that cannot be controlled often continues. The cough is dry at first, and then sputum gradually develops. Sputum is low or not purulent, if any. It does not affect all infected people, but it is estimated to affect about 3-10%.

[Findings suspected of mycoplasma pneumonia]

1) When there is a person with mycoplasma infection in the family

2) When mycoplasma infection is prevalent in nursery schools and kindergartens

3) When coughing continues for a long time

4) When an asthmatic child has prolonged wheezing or repeated seizures despite treatment with bronchodilators, etc.

5) If fever and cough do not go away even after using cephem antibiotics

[Diagnosis of mycoplasma pneumonia]

The diagnosis is a definitive diagnosis with an increase in anti-mycoplasma antibody. Since the specificity of anti-mycoplasma antibody is low, a more specific diagnostic method is desired. Chest radiographs show no segmental findings and tend to show ground-glass interstitial opacities. Since mycoplasma is transmitted by droplets, diagnosis at home, school, workplace, etc. may be effective.


The test looks for a cold agglutination reaction and an increase in anti-mycoplasma antibodies in a blood test. (IDWR: In case of infection) Check chest XP for pneumonia. Chest XP shadows (atypical pneumonia) can be predicted to be mycoplasma pneumonia, but some may show similar images with viral infections. The white blood cell count is often normal, but in some cases it may show a slight increase of about 10,000 to 15,000. It is not helpful because it cannot be detected by the sputum culture test, which is a routine test. CRP often shows a mild increase, but it can also be negative.


Be aware that children with a history of asthma may have or worsen asthma attacks. High fever can also induce seizures (febrile seizures). A rash may appear and otitis media may be complicated. Mycoplasma pneumoniae is myocarditis, epicarditis, nephritis, otitis media, myringitis, erythema multiforme (quite common), Stephen Johnson syndrome, meningitis, encephalitis, polyneuritis, cold agglutinin disease, thrombocytopenia, etc. It can also cause a variety of lesions.


Since mycoplasma does not have a cell wall, cell wall synthesis inhibitors such as β-lactams and aminoglycosides are ineffective. Macrolides, tetracyclines, and ketolides are the first-line drugs. Choose from macrolide antibiotics, Esinol, Claris, Zithromax, etc. Recently, the emergence of resistant bacteria has become a problem.

Cephem antibiotics, which are usually prescribed outpatiently, do not work for mycoplasma. Conversely, macrolide antibiotics that are effective against mycoplasma have the characteristic of being less effective against bacteria. Therefore, whether the pathogen causing the symptom is mycoplasma, bacteria, or virus is a problem especially when treating children.


Hand washing and gargling are also effective because there are infections caused by touching the secretions from the patient's nose and throat and inhaling droplets. It is also important to avoid close contact with the patient. It is said that the period of infectivity is from 1 week before the onset of illness to 10 days after the onset of illness. As for going to school, the acute phase has passed and the symptoms have improved, and those with good general condition can go to school.


The prognosis is generally good, but coughing is often prolonged, often lasting more than a month, and it can take a month or two for the roentgen pneumonia image to improve. Even if you take it once, you may get sick again, and you may not be able to immunize for the rest of your life. If fever continues during the course and vomiting, headache, etc. are observed, it is necessary to consider complication of meningitis. Other reports include otitis media, urethritis, and hepatitis. It is said that children have more complications than adults.


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