Mycoplasma pneumoniae (MP), the smallest pathogenic microorganism between bacteria and viruses known to live independently, is transmitted mainly by droplets and often causes pediatric respiratory disease. Mycoplasma pneumoniae pneumonia (MPP), has been reported to account for approximately 10-40% of community-acquired pneumonia in children and adolescents, with approximately 20% of children over 5 years of age.
I. Clinical symptoms of mycoplasma pneumonia in children
1, fever: most of the acute phase of mycoplasma pneumonia is accompanied by fever, fever peaks at 38-39 ℃, the fever pattern is irregular, most of the fever in more than 1 week, with 1 to 2 weeks is more common.
2. Cough: The cough of mycoplasma pneumonia is initially dry, followed by an irritating, stubborn and violent cough or whooping cough-like cough with a small amount of mucus sputum or no sputum, occasionally with hemoptysis, and older people may complain of pain behind the sternum caused by the cough.
3, wheezing: mycoplasma as a specific antigen, can stimulate the body to produce specific IgE, causing the body metamorphosis, prompting inflammatory cells to release mediators, resulting in wheezing episodes in children.
4, chest X-ray: Mycoplasma pneumonia pulmonary signs are not obvious, all children have abnormal changes in the X-ray plain and CT lung. In children with fever for more than 48 hours, attention should be paid to the possibility that the infection has progressed to the lungs, and chest radiographs should be taken if necessary to clarify the diagnosis.
Laboratory tests
The white blood cell count in children with MPP is normal or mildly elevated, which is different from that of bacterial pneumonia in general, but the C-reactive protein (CRP) is often increased to varying degrees, which can be differentiated from viral pneumonia.
In children with refractory mycoplasma pneumonia (RMPP), the total peripheral blood count, CRP, and sedimentation are significantly higher than those of the common MPP, and some studies have concluded that CRP >40 mg/L (reference value <8 mg/L) is a risk factor associated with RMPP.
III. Drug treatment
1.Macrolide antibacterial drugs
At present, the first choice of drugs for the treatment of MPP in children is macrolide antibacterial drugs, commonly used are erythromycin, azithromycin, clarithromycin and so on. Among them, azithromycin is used in small doses and only needs to be administered once a day, so it has become the first choice for the treatment of MPP.
(1) Erythromycin
The commonly used dose is 20~40mg/kg.d, divided into 3~4 times intravenous drip or oral.
Erythromycin is effective in clearing the signs and symptoms of mycoplasma pneumonia respiratory tract, but it is not effective in eliminating the MP carried in the body, and it is difficult for children to tolerate its gastrointestinal and other adverse effects, which limits the clinical application of erythromycin. Therefore, the commonly used drug in clinical practice is azithromycin.
(2) Azithromycin
For children over 6 months old, the usual oral dose is 10mg/kg.d once/d for 3 days, or 10mg/kg.d on the first day, followed by 5mg/kg.d for 4 days.
Caution should be exercised in the use of azithromycin, especially in intravenous formulations, in children <6 months of age.
If administered intravenously by drip, the drip time should be 3 hours for 1mg/ml and 1 hour for 2mg/ml, and the drip concentration should not be higher than 2mg/ml.
(3) Sequential therapy
Erythromycin sequential therapy: use erythromycin 20~40mg/kg.d intravenously and switch to oral new macrolides (such as azithromycin, clarithromycin) for 2~3 weeks after 5~7 days.
Azithromycin sequential therapy: first intravenous azithromycin 10mgkg.d, 1 time/d for at least 2 days. After intravenous administration, take azithromycin orally, 1 time/d. Total course of intravenous and oral administration 7-10 days.
Erythromycin-azithromycin sequential therapy: Erythromycin is given intravenously for about 10 days, then oral azithromycin is given for 3 days, stopping for 4 days, 7 days is a course of treatment. Depending on the changes of the disease, this regimen is re-negative 2~4 times.
Azithromycin is known to have a high intracellular concentration and a low extracellular concentration. It has been suggested that in the presence of mycoplasmaemia, it may be more effective to choose erythromycin-azithromycin sequential therapy.
So far, there is no uniform standard for clinical application of macrolide antibiotics sequential treatment of MP, all of them are empirical treatment.
2.Cephalosporin antibiotics
Although cephalosporin antibiotics are ineffective against MP lacking cell walls, some studies have shown that the addition of cephalosporins is more effective than macrolides alone in the treatment of refractory Mycoplasma pneumoniae pneumonia ((RMPP), which may be related to the presence of mixed bacterial infections in RMPP.
The significant increase in CRP is generally considered as the presence of bacterial infection.
3.Minocycline
In clinical work, for patients with mycoplasma pneumonia who do not show significant improvement even after 72h of macrolide antimicrobial treatment, the possibility of infection by macrolide resistant strains should be considered. If there is no clear contraindication, the treatment can be switched to tetracycline antibacterial drugs.
Minocycline granules (commonly used at 50 mg/kg.d) were approved in Japan in 2004 for use in children ≥8 years of age with MP infections that are ineffective or unavailable to macrolide antimicrobial therapy.
In the United States and the European Union, the application of minocycline for the treatment of MP infection in children has not been approved, and only doxycycline is currently recommended.
4.Rifampin
In recent years, the rate of MP resistance to macrolides has been increasing, and the combination of rifampicin can be considered for the treatment of those who have poor results with macrolide antibiotics alone.
Rifampicin is a commonly used clinical anti-tuberculosis drug, which acts together with macrolide antibiotics at different stages of protein synthesis, and thus has a synergistic antibacterial effect on MP.
Studies have concluded that the efficacy of small doses and short courses of rifampicin in children with refractory mycoplasma pneumoniae pneumonia (RMPP) is better than that of erythromycin or azithromycin alone.
5. Glucocorticoids
Given that the tissue damage of MP infection includes direct, immune and inflammatory mediator damage, there is a basic consensus that glucocorticoids can be applied when children with MPP have pulmonary atelectasis, interstitial fibrosis, bronchiectasis, or extra-pulmonary complications.
The dosage and course of hormone treatment for RMPP vary in China, mostly mepronil 2mg/kg.d. The initial application is usually 3 d. The dosage is gradually reduced when the body temperature is normal, the solid and pleural effusions improve and the inflammatory indexes decrease, and is discontinued when the condition is stable.
Foreign reports for oral (1mg/kg-d) dose of prednisone ineffective RMPP patients switched to (10mg/kg-d) methylprednisolone continuous intravenous drip 2-3 d, the children’s clinical symptoms and imaging manifestations in a few days after treatment were significantly improved, and no related obvious complications occurred.
6.Gammaglobulin
Compared with normal children, children with congenital hypogammaglobulinemia are more prone to MP infection, and the disease is more likely to be prolonged and may cause joint pain, skin damage, nephritis and other extrapulmonary manifestations.
Gammaglobulin 400 mg/kg.d, administered intravenously for 3 to 5 days, in combination with macrolides, may be effective.
It is currently believed that intravenous gammaglobulin may be considered for the treatment of children with RMPP who have combined respiratory viral infections and low CRP levels in the absence of other effective antiviral therapy.
For children with RMPP in whom low dose (2 mg/kg-d) methylprednisolone therapy has failed due to various factors, in addition to increasing the hormone dose, the combination of gammaglobulin can help improve the clinical outcome.
The above are only recommended medications, please refer to the clinical guidelines for specific treatment and medication.