Recently, there is a trend of a small epidemic of mycoplasma pneumonia, and the age of onset is younger than in previous years. There are more children with mycoplasma pneumonia in the ward and many cases in the online consultation. The manifestations are severe cough, lung signs are not obvious, there are obvious lesions on the chest X-ray, and the disease usually has a long duration and insidious onset. Therefore, parents are often very worried. Knowing the characteristics of this disease at this time can help relieve parents’ tension and ease the state of mistrust between doctors and patients, which is more conducive to recovery from the disease!
Mycoplasma pneumonia in children
Overview]
Mycoplasma pneumonia is caused by mycoplasma infection and is an important cause of pneumonia and other respiratory infections in children.
Etiology
Mycoplasma pneumoniae (mycoplasma Pneumoniae) is a microorganism between bacteria and viruses, the smallest of the pathogenic microorganisms known to live independently, the diameter of the pathogen is 125-150nm, similar in size to the mucovirus, no cell wall, so it is spherical, rod-shaped, filamentous and other multiform, Gram stain negative. Can withstand freezing.
Epidemiology
The disease is mainly transmitted through respiratory droplets, usually seen in epidemic cases, the whole year has the onset. Outbreaks are most common in the spring.
Regional epidemics occur about every 3 to 7 years and are characterized by a long duration, up to one year.
In addition to pneumonia, it can also manifest as bronchitis, tracheitis and pharyngitis.
Many outpatients have mild symptoms and are easily missed if serological tests are not performed.
The disease is more common in school-age children and can also occur in preschoolers, some of whom can carry the pathogen after recovery.
Clinical manifestations
1.Incubation period
About 2 to 3 weeks (8 to 35 days).
2.Symptoms
The severity varies. Most of them have an insidious onset. Often starts with general discomfort.
Most of them have a heavy cough, initially dry, followed by sputum secretion (occasionally with a small amount of blood), sometimes with a paroxysmal cough slightly resembling whooping cough.
There may be fever, anorexia, chills, headache, sore throat, and pain under the sternum.
The body temperature is 37-41℃, mostly around 39℃, and may be persistent or flaccid, or only low fever, or even no fever.
Nausea, vomiting and transient maculopapular rash or urticaria are occasionally seen.
There are usually no signs of respiratory distress, but infant patients may have wheezing and dyspnea.
Older children often lack significant chest signs.
In infants, mild turbid sounds on percussion, decreased breath sounds, wet rales, and sometimes signs of obstructive emphysema may be present.
Mycoplasma pneumonia may occasionally be combined with exudative pleurisy and lung abscess.
There is a relationship between chronic lung disorders and Mycoplasma pneumoniae, such as a 4-fold increase in recovery in some children with asthma.
Mycoplasma pneumonia can be associated with multisystem and multiorgan damage.
Extra-respiratory lesions may involve the skin mucosa and manifest as a measles-like or scarlet fever-like rash, StevensJohnson syndrome, etc.
Non-specific myalgia and wandering arthralgia are occasionally seen.
The gastrointestinal system is characterized by vomiting, diarrhea and hepatic impairment.
Hematologically, hemolytic anemia is more common.
The neurological system may include polyneuritis, meningoencephalitis and cerebellar damage.
Cardiovascular system lesions occasionally include myocarditis and pericarditis.
Bacterial infections may also be mixed.
Leukocyte levels vary, mostly normal, sometimes high. Blood sedimentation shows moderate increase.
3.X-ray examination
Most of the lesions are unilateral, accounting for more than 80%, mostly in the lower lobe.
Sometimes only the hilar shadow is increased.
Most of them show irregular cloudy pulmonary infiltrates, extending outward from the hilum to the lung fields, especially common in the lower lobes of both lungs, and a few are large lobar solid shadows.
Pulmonary atelectasis may be seen.
The infiltrates often dissipate in one area while new infiltrates occur elsewhere.
Sometimes there is a bilateral diffuse reticular or nodular infiltrative shadow or interstitial pneumonia without solid lung segments or lobar changes.
The mild signs and significant chest radiograph shadows are one of the features of the disease.
4.Course of disease
The natural course of the disease varies from 2 to 4 weeks, with most of the fever subsiding in 8 to 12 days and the recovery period taking 1 to 2 weeks.
The complete disappearance of x-ray shadows takes longer than the disappearance of symptoms, often extending 2 to 3 weeks. Occasionally, recurrence is seen.
[Diagnosis
The main points of diagnosis are.
① Persistent severe cough with unremarkable pulmonary signs and more significant X-ray findings.
If several cases occur at the same time in older children, it is suspected to be an epidemic case and the diagnosis can be confirmed early.
②White blood cell count is mostly normal or slightly increased, blood sedimentation is mostly increased and Coombs test is positive.
(③) Penicillin, streptomycin and cephalosporins are ineffective.
④Serum agglutinin (IgM type) titers mostly rise to 1:32 or higher, with a positive rate of 50% to 75%, and the more severe the disease, the higher the positive rate.
Cold agglutinin mostly starts to appear at the end of the first week after the onset of the disease, peaks at the third to fourth week, and then decreases and disappears in two to four months. This is a non-specific reaction, also seen in liver disease, hemolytic anemia, infectious mononucleosis, etc., but its titer generally does not exceed 1:32.
⑤ Serum-specific antibody assay has diagnostic value, and in addition, enzyme-linked adsorption test can be used to detect the antigen.
In recent years, domestic and foreign applications of DNA probes and PCR detection of Mycoplasma pneumoniae DNA diagnosis has the advantage of high rapidity and specificity.
(6) It takes too long to culture mycoplasma with patient sputum or pharyngeal washings, often 2-3 weeks, so it is not very helpful for clinical purposes.
Differential diagnosis
The disease must sometimes be differentiated from the following diseases.
①Tuberculosis;
②Bacterial pneumonia;
③Pertussis;
④Typhoid fever;
⑤ Infectious mononucleosis;
(6) Rheumatic pneumonia.
All of them can be differentiated based on medical history, tuberculin test, X-ray follow-up observation and bacteriological examination and serological reaction.
Therapeutic measures
The treatment principle is basically the same as that of general pneumonia, and comprehensive treatment measures are taken.
It includes general treatment, symptomatic treatment, application of antibiotics, adrenocorticosteroids, and treatment of extra-pulmonary complications.
1.General treatment
(1) Respiratory isolation
Because mycoplasma infection can cause a small epidemic, and the time of mycoplasma discharge after the disease in children is long, up to 1 to 2 months beyond.
In infancy, only symptoms of upper respiratory tract infection are manifested, and pneumonia occurs only after repeated infections.
At the same time, it is easy to reinfect with other viruses during MP infection, leading to aggravation and prolongation of the disease.
Therefore, respiratory isolation of the affected child or children with a history of close contact should be done as much as possible to prevent reinfection and cross-infection.
(2) Care
Keep indoor air fresh, supply easily digestible, nutritious food and sufficient fluids.
Keep the oral hygiene and respiratory tract unobstructed, turn the child frequently, pat the back and change the position to promote the discharge of secretions, and if necessary, suction appropriately to remove mucous secretions.
(3) Oxygen therapy
For those who have severe disease with hypoxia, or those with serious airway obstruction, oxygen should be given in time.
The purpose is to increase the partial pressure of arterial blood oxygen and improve the tissue hypoxia caused by hypoxemia.
The method of oxygen administration is the same as that for general pneumonia.
2.Symptomatic treatment
(1) Expectoration of sputum
The purpose is to make the sputum thin and easy to expel, otherwise it is easy to increase the chance of bacterial infection.
However, there are few effective expectorants. In addition to strengthening turning, back patting, nebulization and sputum aspiration, the following can be used
In addition to strengthening turning, back patting, nebulization and sputum aspiration, expectorants such as Bixuping, Sputum Easy, Mucosolvan and Genoton can be used.
As cough is the most prominent clinical manifestation of mycoplasma pneumonia, frequent and violent coughing will affect the sleep and rest of the child.
Sedatives such as chloral hydrate or phenobarbital can be given appropriately, and small doses of central cough suppressants can be given as appropriate, but not too many times.
(2) Calming asthma
For severe wheezing, bronchodilators, such as aminophylline, can be used orally, 4-6mg/(kg/time), once every 6h;
Inhalation of albuterol can also be used.
3.Application of antibiotics
According to the microbiological characteristics of MP, any antibiotics such as penicillin that can impede the synthesis of microbial cell walls are ineffective against mycoplasma.
Therefore, for the treatment of MP infection, antibiotics that can inhibit protein synthesis should be used, including macrolide tip, tetracycline, chloramphenicol and so on.
In addition, lincomycin, clindamycin, vancomycin and sulfonamides such as SMZxo are also available.
(1) Macrolide antibiotics
Macrolide antibiotics such as erythromycin, spiramycin, methicillin, and leucomycin are often used in the above.
Among them, erythromycin is the first choice, the drug is widely used, the efficacy is sure.
It is obvious for eliminating the signs and symptoms of mycoplasma pneumonia, but the effect of eliminating MP is not ideal and cannot eliminate the host of Mycoplasma pneumoniae.
Commonly used dose is 30~50mg/(kg・d), mild cases can be treated orally in divided doses, serious cases can be considered for intravenous administration, the course of treatment is generally advocated not less than 2~3 weeks, stopping the drug too early is easy to relapse.
Oral erythromycin is absorbed from the intestinal tract. 250mg of erythromycin is taken on an empty stomach, and the peak blood concentration reaches 0.3-0.7μg/ml 2-3h after administration; the dose is doubled, and the peak blood concentration is 0.3-1.9μg/ml.
If 300mg of erythromycin lactate was administered intravenously, the average blood concentration was 40.9μg/ml at 4min, 2.6μg/ml after 2h and 0.32μg/ml after 6h. If 1g of erythromycin lactate was administered intravenously continuously every 12h, the blood concentration could be maintained at 4-6μg/ml after 8h. And the average attempt in sputum was 2.6(0.9-8.4)μg/ml. ml.
Erythromycin is excreted mainly via the bile and partially reabsorbed from the intestine. A considerable amount of erythromycin is metabolically inactivated in the liver.
2.5% of the oral dose and 15% of the injectable dose are excreted in the urine as the active substance.
Erythromycin is not removed from the body by either hemodialysis or peritoneal dialysis.
When using erythromycin preparations, attention should be paid to its toxic effects.
All oral preparations can cause nausea, vomiting, abdominal pain, diarrhea and other gastrointestinal symptoms;
Thrombophlebitis may occur during intravenous infusion;
Occasionally, allergic reactions may occur, manifesting as drug fever and urticaria.
It is worth noting that red jaundice, often in the administration of 14 to 21 days produce epigastric pain, nausea and vomiting, followed by fever, jaundice, leukocytes and eosinophilia, increased serum bilirubin and transaminases, 2 to 3 days after discontinuation of the drug can return to normal, but re-administration of the drug can reappear above symptoms.
In addition, the application of high doses of erythromycin may occasionally cause tinnitus and temporary hearing impairment, which usually occurs when administered intravenously or in the presence of renal decompensation and/or liver damage.
If used with theophylline drugs, it has the effect of increasing theophylline and blood concentration. Therefore, when combined with theophylline drugs, the use should be reduced or avoided.
In view of erythromycin’s high irritation to the gastrointestinal tract, and can cause an increase in blood bilirubin and transaminases, and there are reports of drug-resistant strains.
People began to choose macrolides of new production mouth, such as roxithromycin (roxithromycin) and methylerythromycin (clarithromycin), azithromycin (azithromycin), etc., oral easy to tolerate, strong penetrating ability of tissue, can penetrate into the cells, long half-life, MIC of 0.002 ~ 0.03mg / L.
In recent years, the use of leucomycin in Japan for the treatment of this disease is more effective, the drug has no significant toxic side effects, relatively safe, oral dose of 20 ~ 40mg/(kg・d), divided into four doses; static drip amount of 10 ~ 20mg/(kg・d).
(2) Tetracycline antibiotics
Although MP infection has a positive effect, but its toxic side effects are more, especially tetracycline on bone and tooth growth, even for a short period of time, the pigment of tetracycline can be combined with the newly formed bone and calcium in the teeth, so that the milk teeth yellow stained. Therefore, it should not be applied during childhood before the age of 7.
(3) Chloramphenicol and iopamide-based
Because the course of treatment of MP infection is long, and chloramphenicol and sulfonamide antibacterial drugs have more toxic side effects and should not be used for a long time, so they are less used clinically to treat MP infection.
(4) Fluoroquinolones
In recent years, fluoroquinolones (fluroqumolone) have been reported for the treatment of MP infection. Fluroqumolone is a synthetic antibacterial drug, which exerts antibacterial effects by inhibiting DNA rotase and blocking DNA replication.
Ciproflaxacin and ofloxacin are highly concentrated in lung and bronchial secretions, penetrate the cell wall, and have a half-life of 6.7-7.4 h. They have a broad antibacterial spectrum and are very effective in treating MP. The former 10~15mg/(kg・d), divided into 2~3 times orally, also can be divided into static drip; the latter 10~15mg/(kg・d), divided into 2~3 times orally, the course of treatment 2~3 weeks.
4. Application of adrenal glucocorticoids
It is believed that MP pneumonia is an immune response of the human immune system to MP.
Therefore, for the rapid development of the acute stage of the disease, severe MP pneumonia, or lung lesions are extended, and pulmonary atelectasis, interstitial fibrosis, bronchial dilatation, or extra-pulmonary complications, adrenal corticosteroids can be applied.
For example, hydrocortisone or hydrocortisone succinate, 5-10mg/kg each time, IV; or dexamethasone 0.1-0.25mg/(kg・time), IV; or prednisone 1-2mg/(kg・d), divided into oral doses, the general course of treatment 3-5d.
Pay attention to the discharge of tuberculosis and other infections when applying hormones.
5.Treatment of extra-pulmonary complications
Currently, the occurrence of complications is thought to be related to immune mechanisms.
Therefore, in addition to active treatment of pneumonia and control of MP infection, hormones can be used according to the condition.
Different symptomatic treatment methods are used for different complications.
Prevention
In recent years, many studies have been conducted abroad on Mycoplasma pneumoniae vaccines, and inactivated and live attenuated vaccines have been prepared.
Wenzel (1977) observed formalin-inactivated Mycoplasma pneumoniae vaccine, which had some effect.
[Prognosis].
Attention should be paid to rest, care and diet.
If necessary, small amounts of antipyretics, and herbal medicines can be taken.
Other symptomatic treatments are the same as for bronchitis.
Mycoplasma is sensitive to tetracycline and macrolide antibiotics.
Erythromycin is the drug of choice, the dose of 30mg/(kg・d), oral three times a day, can improve the clinical symptoms, reduce the lung shadow, and can shorten the course of the disease. The course of erythromycin is 2 to 3 weeks.
In addition, mecamycin, rifampin and acetylspiramycin are also effective.
Adrenocorticotropic hormone may be added in children with severe disease.
The prognosis is good, and although the course of the disease is sometimes long, it can eventually recover completely.
Complications are rare, with otitis media, pleural exudate, hemolytic anemia, myocarditis, pericarditis, meningoencephalitis, and cutaneous mucosal syndrome only occasionally seen.
However, recurrence is occasionally possible, and sometimes pulmonary lesions and pulmonary function are slow to recover.