Bronchoalveolar lavage T cell cytokine profiles and their association with lung function in children with Mycoplasma pneumoniae -associated bronchiolitis obliterans

Integrative study of pulmonary microbiome, transcriptome and clinical outcomes in Mycoplasma pneumoniae pneumonia

BACKGROUND

This study aimed to investigate the interactions among three core elements of respiratory infection-pathogen, lung microbiome, and host response-and their avocation with the severity and outcomes of Mycoplasma pneumoniae pneumonia (MPP) in children.

METHODS

We prospectively collected bronchoalveolar lavage fluid from a cohort of 41 children with MPP, including general MPP (GMPP) and complicated MPP (CMPP), followed by microbiome and transcriptomic analyses to characterize the association among pathogen, lung microbiome, and host response and correlate it with the clinical features and outcomes.

RESULTS

The lung microbiome of patients with CMPP had an increased relative abundance of Mycoplasma pneumoniae (MP) and reduced alpha diversity, with 76 differentially expressed species. Host gene analysis revealed a key module associated with neutrophil function and several inflammatory response pathways. Patients with a high relative abundance of MP, manifested by a specific lung microbiome and host response type, were more prone to CMPP and had a long imaging recovery time.

CONCLUSION

Patients with CMPP have a more disrupted lung microbiome than those with GMPP. MP, lung microbiome, and host response interacts with each other and are closely related to disease severity and outcomes in children with MPP.

Pseudomembranous necrotizing laryngotracheobronchitis due to Mycoplasma pneumoniae: a case report and literature review

Background

Pseudomembranous necrotizing laryngotracheobronchitis refers to an acute diffuse necrotizing inflammation in the mucosa of the larynx, trachea, and bronchus. It often occurs in infants and children having viral infections secondary to bacterial infections. Mycoplasma pneumoniae (M. pneumoniae) is a common pathogen that causes pneumonia in children. In recent years, serious complications due to M. pneumoniae infection, including necrotizing pneumonia, pulmonary embolism, and pleural effusion, have been increasingly reported.

Case presentation

An 11-year-old girl was admitted to our unit with cough, fever, and hoarseness persistent for a week. The results of the M. pneumoniae serological test, PCR examination with bronchial aspirate and bronchoalveolar lavage fluid (BALF), next-generation sequencing (mNGS) for BALF, all suggested the presence of M. pneumoniae infection. High-resolution CT scanning of the chest showed inflammation of the middle and lower lobes of the right lung. By bronchoscopy, the necrosis of the vocal cords, trachea, and bronchial mucosa was observed; each bronchial lumen contained a large amount of white viscous sputum. Pathological findings for bronchial mucosa suggested inflammatory necrosis. After administration of azithromycin and glucocorticoids, the symptoms of the patients were ameliorated. After 2 weeks post-discharge, the X-ray scan of her chest indicated the pneumonia resolution in the right lung.

Conclusions

In patients with pneumonia due to M. pneumoniae infection, which causes obvious hoarseness, bronchoscopy is necessary even if the lung lesions are not massively consolidated. When necrotizing lesions of the larynx, trachea, and bronchi are detected by bronchoscopy, the necrotic tissues in the corresponding parts should be conducted tissue biopsy for pathological examination. Apart from macrolide antibiotics, the administration of small doses of glucocorticoids is necessary.

IL-17 stimulates neutrophils to release S100A8/A9 to promote lung epithelial cell apoptosis in Mycoplasma pneumoniae-induced pneumonia in children

Mycoplasma pneumoniae-induced pneumonia (MPP) is a common cause of community-acquired respiratory tract infections, increasing risk of morbidity and mortality, in children. However, diagnosing early-stage MPP is difficult owing to the lack of good diagnostic methods. Here, we examined the protein profile of bronchoalveolar lavage fluid (BALF) and found that S100A8/A9 was highly expressed. Enzyme-linked immunosorbent assays used to assess protein levels in serum samples indicated that S100A8/A9 concentrations were also increased in serum obtained from children with MPP, with no change in S100A8/A9 levels in children with viral or bacterial pneumonia. In vitro, S100A8/A9 treatment significantly increased apoptosis in a human alveolar basal epithelial cell line (A549 cells). Bioinformatics analyses indicated that up-regulated S100A8/A9 proteins participated in the interleukin (IL)-17 signaling pathway. The origin of the increased S100A8/A9 was investigated in A549 cells and in neutrophils obtained from children with MPP. Treatment of neutrophils, but not of A549 cells, with IL-17A released S100A8/A9 into the culture medium. In summary, we demonstrated that S100A8/A9, possibly released from neutrophils, is a new potential biomarker for the clinical diagnosis of children MPP and involved in the development of this disease through enhancing apoptosis of alveolar basal epithelial cells.

Biological functions of IL-17-producing cells in mycoplasma respiratory infection

Mycoplasmas are the smallest and simplest bacteria that lack a cell wall but have the capability of self-replication. Among them, Mycoplasma pneumoniae is one of the most common causes of community-acquired pneumonia. The hallmark of mycoplasma respiratory diseases is the persistence of lung inflammation that involves both innate and adaptive immune responses. In recent years, a growing body of evidence demonstrates that IL-17 plays an important role in respiratory mycoplasma infection, and associates with the pathologic outcomes of infection, such as pneumonitis and asthma. Numerous studies have shown that a variety of cells, in particular Th17 cells, in the lung can secrete IL-17 during respiratory mycoplasma infection. In this article, we review the biological functions of distinct IL-17-producing cells in mycoplasma respiratory infection with a focus on the effect of IL-17 on the outcomes of infection.