OVERVIEW
广义指人体感染肺炎支原体，狭义指感染支原体后发病
多数仅以低热、疲乏起病，也可出现全身中毒症状
肺炎支原体入侵人体
早期用抗生素可减轻症状、缩短病程，首选大环内酯类抗生素
Definition.
When an organism is infected with Mycoplasma pneumoniae, it is referred to as a Mycoplasma pneumoniae infection, including latent infection and morbidity, which is the broad definition; the resulting series of diseases is called Mycoplasma pneumoniae infectious diseases, such as Mycoplasma pneumoniae.
However, in everyday life, Mycoplasma pneumoniae infection is often defaulted to Mycoplasma pneumoniae infectious disease, which is also a narrow definition, and this entry also uses this definition as the focus of the introduction.
Mycoplasma pneumoniae infectious disease includes a variety of lesions both inside and outside the lungs. Intrapulmonary lesions usually cause acute lung inflammation with predominantly interstitial lesions [1], and extrapulmonary lesions may manifest as damage to the skin mucosa, hematologic system, and digestive system.
Morbidity
Infection rate
The onset of Mycoplasma pneumoniae infection usually causes Mycoplasma pneumoniae pneumonia, which accounts for about one-third of non-bacterial pneumonias and 15% to 18% of adult pneumonias, second only to streptococcal pneumonia [1].
In a recent survey in the United States, Mycoplasma pneumoniae pneumonia was the most common bacterium in about 15% of children over 5 years of age with community-acquired pneumonia [2].
About 20% of Mycoplasma pneumoniae infections are occult, that is, without clinical symptoms [3].
Disease distribution
Most common in summer and fall.
It is more common in adolescents.
Etiology
Causes
Source of infection
Mycoplasma pneumoniae infection is caused by the invasion of Mycoplasma pneumoniae into the human body, and those who have the disease and those who have hidden infection are the main sources of infection.
Transmission
It is weakly contagious and spreads mainly through respiratory droplets or aerosols. Healthy people are infected by inhaling the oral and nasal secretions spewed out by the patient when coughing or sneezing, which may cause epidemiologic transmission in a small area [4].
Mycoplasma pneumoniae can be detected in nasal, pharyngeal, laryngeal, and tracheal secretions 2-3 days before, during, and 3-5 weeks after the onset of illness, with the first 4-6 days of the onset phase being the most infectious [1].
Susceptible population
It is universally susceptible, but the onset of the disease is more common in people aged 5 to 30 years, and most common in adolescents aged 10 to 19 years.
The onset of the disease can stimulate the body to produce antibodies, and most people over 50 years of age have antibodies, which can reduce the risk of re-infection, but cannot eliminate re-infection [5].
Predisposing factors
Rain, cold, sudden changes in climate, and overwork can reduce the local defense function of the respiratory tract and lead to morbidity.
Pathogenesis
After invading the respiratory tract, Mycoplasma pneumoniae first adheres to the neuraminic acid receptors on the surface of respiratory epithelial cells with the help of surface proteins and moves to the basal part of the cilia, so that the mycoplasma is protected from the removal of the ciliary system and evades the phagocytosis of phagocytes [6].
By inducing immune damage and releasing toxic metabolites such as hydrogen peroxide (H2O2) and superoxide, Mycoplasma pneumoniae causes destruction of the bronchial and fine bronchial mucosal layers, weakening or even disappearance of cilia movement, and may involve the interstitium and alveolar walls, resulting in a series of symptoms.
Symptoms
After Mycoplasma pneumoniae infection, symptoms do not appear immediately, there may be an incubation period of 2 to 3 weeks, with a slow onset.
Main Symptoms
Typical symptoms
Symptoms mainly include fever, cough, malaise, headache, sore throat and muscle aches.
The fever is usually moderate, and a few people do not have fever or develop high fever. Fever may last for 2 to 3 weeks, and the cough may remain after the body temperature returns to normal.
The cough is mostly episodic dry cough, obvious at night, and may also produce purulent sputum [7-8], and the persistent paroxysmal severe cough is a more typical manifestation of mycoplasma pneumonia.
Extrapulmonary manifestations
are more common and may cause damage to multiple systems.
Skin and mucous membrane damage: e.g. maculopapular rash, erythema multiforme.
Ear and nose damage: nasal and ear pain may occur.
Digestive system damage: such as nausea, vomiting, diarrhea, and loss of appetite.
Complications
The disease is usually mild and complications are relatively rare.
In severe cases, complications may occur in different systems, such as lung abscess, pneumothorax, emphysema, bronchiectasis, occlusive bronchiolitis, meningitis, cardiac insufficiency, ARDS (Acute Respiratory Distress Syndrome), DIC (Disseminated Intravascular Coagulation).
Consultation
Department of Medicine
Respiratory Medicine
If symptoms such as cough, sputum, dyspnea and chest pain are evident, you can seek prompt medical attention at the department of respiratory medicine [6].
Infectious diseases
Fever, rash, and cough can also be treated in the Department of Infectious Diseases.
Emergency Medicine
If symptoms such as high fever and respiratory distress occur, you should promptly go to the emergency department or call 120 emergency number.
Preparation for medical treatment
Preparation for medical treatment: registration, preparation of documents, common problems.
Tips for seeking medical treatment
Avoid taking fever-reducing medication or antibiotics by yourself before going to the doctor, so as not to influence the doctor’s judgment of the condition.
Patients with high fever can first take physical cooling, such as applying cold compresses to the forehead and wiping the hands, feet and armpits with lukewarm water.
Chest X-rays or chest CTs are often needed, so avoid wearing clothes made of metal, and inform your doctor if you are pregnant or preparing for pregnancy.
Preparation Checklist
症状清单
Pay particular attention to the time of onset of symptoms and special manifestations.
Is there fever? What is the highest degree?
Is there nasal congestion and runny nose? What is the color and nature of the nasal discharge?
Is there a cough? How long has the cough lasted?
Is there any phlegm? What kind of phlegm?
Is there any other discomfort?
How long have the symptoms lasted? Any aggravating or relieving factors?
病史清单
Have you been exposed to cold or exertion recently?
Have you been in contact with anyone with a cold or fever before the onset of the illness?
Are there any chronic diseases such as diabetes mellitus or chronic obstructive pulmonary disease?
Are there any long-term oral medications such as glucocorticoids and immunosuppressants?
检查清单
Test results in the past six months, which can be carried to the doctor
Laboratory tests: blood routine, C-reactive protein, Mycoplasma pneumoniae culture, cold agglutination test, mycoplasma-specific antibody, calcitoninogen, sputum bacterial culture and drug sensitivity test, influenza and parainfluenza viral nucleic acid, novel coronavirus nucleic acid.
Imaging tests: chest X-ray, chest CT.
用药清单
Medication in the last 3 months, if available, bring the box or package to the doctor’s office
Antibiotics: e.g. penicillin, cefaclor, ceftazidime, azithromycin, moxifloxacin, vancomycin, etc.
Antipyretics and analgesics: e.g., ibuprofen, acetaminophen, etc.
Nasal decongestants: such as pseudoephedrine nasal drops.
Phlegmolytic drugs: e.g., Ambroxol, etc.
Diagnosis
Diagnosis
Diagnosis should be based on a combination of clinical symptoms, X-ray imaging and serologic findings.
Medical history
A history of contact with patients with Mycoplasma pneumoniae is informative for the diagnosis of the disease when there is an epidemic of respiratory infections with pneumonia in the family or in a group.
Clinical features
Slow onset, fever, malaise, paroxysmal irritating cough, no sputum or a small amount of mucus sputum, lung signs are not obvious, occasionally wet rales, while the lesions seen on lung X-ray are significant. Or hemorrhagic herpetic otitis media on the basis of the above manifestations, suspicious diagnosis of Mycoplasma pneumoniae.
Pathogenetic examination
Positive serum agglutination test is diagnostic. Positive serum complement binding test or other serologic tests after 10 days of illness are more important for diagnosis.
Isolation of Mycoplasma pneumoniae in nasopharyngeal washings and sputum cultures can confirm the diagnosis.
Detection of Mycoplasma pneumoniae protein antigen in sputum or pharyngeal swabs by monoclonal antibody immunoblotting assay (MAIA) or positive nucleic acid detection of Mycoplasma pneumoniae by PCR can be an important reference for confirming the diagnosis [9-10].
Imaging
Both chest radiographs and chest CT can show different imaging changes of lung lesions.
In the early stage, it is characterized by increased pulmonary striations and reticulated shadows, and then develops into speckled or flaky, uniform or irregular fuzzy shadows, which are denser in the hilar region, and gradually become shallower outward and fan-shaped distribution.
Mostly one lobe is involved, the left lower lobe is most common, and a few are multilobar lesions. A small amount of pleural effusion may be present.
Differential diagnosis
Early manifestations of this disease are not specific, and the manifestations are more complicated when combined with bacterial, fungal or viral infections, and should be distinguished from the following diseases.
1. Viral pneumonia
Respiratory infections caused by influenza virus, parainfluenza virus, SRAS, EBV, CMV, respiratory syncytial virus (RSV) and other viruses are similar to Mycoplasma pneumoniae in their early manifestations.
However, the symptoms of viral pneumonia are often milder, and the onset of the disease may be rapid or slow, with high or low fever.
The key to differentiation is to carry out pathogenetic examination.
2. Legionella pneumonia
Legionella inflammation is characterized by cough, fever, muscle pain and other symptoms, nausea, vomiting and other gastrointestinal symptoms, and even neuropsychiatric symptoms.
Confirmation of diagnosis depends on positive sputum culture or bronchial secretion examination, and serologic detection of Legionella antibody is of diagnostic reference significance.
3. Allergic pneumonia
The symptoms of allergic pneumonia are similar to those of Mycoplasma pneumoniae when there are fever and cough.
However, allergic pneumonitis is a transient alveolar allergic reaction; lung X-ray imaging shows transient, wandering inflammatory infiltration-like changes, which often disappears in 1 week or so; peripheral blood eosinophils are often increased (up to 10% to 70%), and IgE can be increased.
Combined with epidemiologic history or history of drug use, and the indicators of Mycoplasma pneumoniae infection are negative, which helps the differential diagnosis.
Treatment
Aim of treatment: cure the disease, control or relieve symptoms, and prevent complications.
Treatment principle: According to the age and severity of the infected patient, use appropriate antibiotics as early as possible and give symptomatic treatment at the same time.
General treatment
Pay attention to isolation, disinfection and prevention of cross-infection.
Take bed rest and keep air circulation in the living room.
Supplement protein appropriately, such as milk, lean meat, fish and eggs.
Drink more water as appropriate.
Keep the respiratory tract unobstructed.
Medication
Pathogen treatment
Mycoplasma pneumoniae has no cell wall, so it is sensitive to tetracyclines, macrolides and quinolones that interfere with the synthesis of membrane proteins and cytoplasmic proteins.
Macrolides are preferred, and the therapeutic effect of azithromycin on Mycoplasma pneumoniae is the strongest of the macrolides.
For macrolide-resistant patients, tetracycline antibiotics such as doxycycline and minocycline can be used; or quinolone antibiotics such as ciprofloxacin, levofloxacin, lomefloxacin and gatifloxacin can be used.
Tetracyclines and fluoroquinolones are contraindicated in pregnant women and children under 8 years of age.
Drugs should be administered as early as possible, and care should be taken to prevent and control adverse reactions to antimicrobial drugs during treatment.
Symptomatic treatment
For severe cough, cough suppressants such as compound licorice tablets and dextromethorphan can be used.
If the sputum is thick, expectorant drugs such as bromhexine can be used.
If the phlegm is thick, use phlegm-modifying drugs, such as Ambroxol.
Other medications
In severe cases, glucocorticoids may be used to control inflammation, such as methylprednisolone; gammaglobulin may also be used.
Prognosis
Cure
There is a risk of re-infection, whether treated or not.
Untreated
The prognosis is generally good for young adults with no underlying disease.
Some elderly, frail patients with underlying disease may develop serious complications that can kill the patient, but the mortality rate is relatively low.
After treatment
With prompt and correct treatment, the vast majority of patients can be cured.
Prognostic factors
Alcoholism, smoking, advanced age, and immunosuppressed status can lead to a worse prognosis.
Hazards
Viral infections can be spread by droplet transmission, with the potential for group morbidity.
Presence of underlying diseases, such as chronic obstructive pulmonary disease (COPD), asthma, bronchiectasis, nephritis, etc., can induce acute exacerbations after respiratory infections.
Symptoms last for a long time, and nasal congestion, cough, fever and other symptoms are severe enough to affect work and life.
Daily
Daily Management
Daily life management
Close contact with immunocompromised people such as pediatrics, the elderly, and pregnant women should be avoided as much as possible. Wear a mask and cover the mouth and nose when coughing to prevent transmission.
Rest in bed during fever and reduce physical exertion. After the fever subsides, you can resume activities gradually. Use warm water baths and cold compresses to help lower the body temperature when the fever develops, and measure the temperature regularly.
Maintain a good work routine, ensure sufficient sleep time, and avoid exertion and staying up late.
Ventilate the room, and keep the temperature and humidity at a suitable level to minimize cold air and other stimuli and prevent cold.
If you already have high blood pressure, diabetes and other diseases, you need to follow the doctor’s requirements, the full amount of regular medication, and follow up on time, do not stop taking medication on your own because of symptomatic relief, to avoid relapse.
Diet management
Pay attention to balanced nutrition and eat a light diet with more protein, vegetables and fruits.
Eat less high salt and fried food. Abstain from alcohol, strong tea and coffee, and avoid raw garlic, ginger, chili peppers and curry.
Drink an adequate amount of water, 7 to 8 glasses (1500 to 1700 ml) per day for adults, and advocate drinking plain water and tea, no or less sugary drinks.
Smoking cessation
Strictly quit smoking and avoid exposure to “second-hand smoke”.
Disease monitoring
Measure body temperature.
Cough and other symptoms have been reduced, such as coughing less frequently, sputum volume decreased; whether the respiratory rate has increased.
Decrease in activity tolerance.
Follow-up
Regular follow-ups can help to understand the changes in the condition and the recovery situation. Chest CT is usually repeated after 2 weeks of treatment.
Follow your doctor’s recommendations for regular follow-up.
If symptoms worsen, or new symptoms appear, consult your doctor.
Prevention
Most pneumonias cannot be completely prevented, but proper protection can reduce the chance of developing the disease.
Avoid contact with patients with respiratory infections when going out, avoid gathering in crowds, wash your hands frequently, and do not share cups and utensils.
Exercise in moderation. It is recommended to do more aerobic exercises such as jogging, swimming, brisk walking, yoga, square dancing, etc. to improve your physical condition.
参考文献
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李兰娟，王宇明. 感染病学. 人民卫生出版社, 2015.
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Kutty, Preeta K , Jain, et al. Mycoplasma pneumoniae Among Children Hospitalized With Community-acquired Pneumonia.
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葛均波，徐永健，等.内科学[M].第9版.北京：人民卫生出版社.2018.
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美国CDC网站：https://www.cdc.gov/pneumonia/atypical/mycoplasma
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Diaz MH, Benitez AJ,et al. Molecular Detection and Characterization of Mycoplasma pneumoniae Among Patients Hospitalized With Community-Acquired Pneumonia in the United States. Open Forum Infect Dis. 2015 Jul 16;2(3):ofv106.
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Petrone BL, Wolff BJ, et al. Isothermal Detection of Mycoplasma pneumoniae Directly from Respiratory Clinical Specimens. J Clin Microbiol. 2015 Sep;53(9):2970-6.