Impact of atopy on the severity and extrapulmonary manifestations of childhood Mycoplasma pneumoniae pneumonia

Exploring the pathogenetic mechanisms of Mycoplasmapneumoniae (Review)

Mycoplasmas, the smallest self-replicating prokaryotes without a cell wall, are the most prevalent and extensively studied species in humans. They significantly contribute to chronic respiratory tract illnesses and pneumonia, with children and adolescents being particularly vulnerable. Mycoplasma pneumoniae (M. pneumoniae) infections typically tend to be self-limiting and mild but can progress to severe or even life-threatening conditions in certain individuals. Extrapulmonary effects often occur without pneumonia, and both intrapulmonary and extrapulmonary complications operate through separate pathological mechanisms. The indirect immune-mediated damage of the immune system, vascular blockages brought on by vasculitis or thrombosis and direct harm from invasion or locally induced inflammatory cytokines are potential causes of extrapulmonary manifestations due to M. pneumoniae. Proteins associated with adhesion serve as the primary factor crucial for the pathogenicity of M. pneumoniae, relying on a specialized polarized terminal attachment organelle. The type and density of these host receptors significantly impact the adhesion and movement of M. pneumoniae, subsequently influencing the pathogenic mechanism and infection outcomes. Adjacent proteins are crucial for the proper assembly of the attachment organelle, with variations in the genetic domains of P1, P40 and P90 surfaces contributing to the variability of clinical symptoms and offering new avenues for developing vaccines against M. pneumoniae infections. M. pneumoniae causes oxidative stress within respiratory tract epithelial cells by adhering to host cells and releasing hydrogen peroxide and superoxide radicals. This oxidative stress enhances the vulnerability of host cells to harm induced by oxygen molecules. The lack of superoxide dismutase and catalase of bacteria allows it to hinder the catalase activity of the host cell, leading to the reduced breakdown of peroxides. Lung macrophages play a significant role in managing M. pneumoniae infection, identifying it via Toll-like receptor 2 and initiating the myeloid differentiation primary response gene 88-nuclear factor κΒ signaling cascade. However, the precise mechanisms enabling M. pneumoniae to evade intracellular host defenses remain unknown, necessitating further exploration of the pathways involved in intracellular survival. The present comprehensive review delves into the pathogenesis of M. pneumoniae infection within the pulmonary system and into extrapulmonary areas, outlining its impact.

Mycoplasma pneumoniae carriage in children with recurrent respiratory tract infections is associated with a less diverse and altered microbiota

BACKGROUND

Mycoplasma pneumoniae is a common cause of community-acquired pneumonia in school-aged children and can be preceded by asymptomatic carriage. However, its role in recurrent respiratory tract infections is unclear. We studied the prevalence of M.pneumoniae carriage in children with recurrent respiratory infections and identified associated factors.

METHODS

We tested M.pneumoniae carriage by qPCR in children with recurrent infections and their healthy family members in a cross-sectional study. Serum and mucosal total and M.pneumoniae-specific antibody levels were measured by ELISA and nasopharyngeal microbiota composition was characterized by 16S-rRNA sequencing.

FINDINGS

Prevalence of M.pneumoniae carriage was higher in children with recurrent infections (68%) than their family members without infections (47% in siblings and 27% in parents). M.pneumoniae carriage among family members appeared to be associated with transmission within the household, likely originating from the affected child. In logistic regression corrected for age and multiple comparisons, IgA (OR 0.16 [0.06-0.37]) and total IgG deficiency (OR 0.15 [0.02-0.74]) were less prevalent in M.pneumoniae carriers (n = 78) compared to non-carriers (n = 36). In multivariable analysis, the nasopharyngeal microbiota of M.pneumoniae carriers had lower alpha diversity (OR 0.27 [0.09-0.67]) and a higher abundance of Haemophilus influenzae (OR 45.01 [2.74-1608.11]) compared to non-carriers.

INTERPRETATION

M.pneumoniae carriage is highly prevalent in children with recurrent infections and carriers have a less diverse microbiota with an overrepresentation of disease-associated microbiota members compared to non-carriers. Given the high prevalence of M.pneumoniae carriage and the strong association with H. influenzae, we recommend appropriate antibiotic coverage of M.pneumoniae and H. influenzae in case of suspected pneumonia in children with recurrent respiratory tract infections or their family members.

FUNDING

Wilhelmina Children's Hospital Research Fund, 'Christine Bader Stichting Irene KinderZiekenhuis', Sophia Scientific Research Foundation, ESPID Fellowship funded by Seqirus, Hypatia Fellowship funded by Radboudumc and The Netherlands Organisation for Health Research and Development (ZonMW VENI grant to LM Verhagen).

Clinical features of severe Mycoplasma pneumoniae pneumonia with pulmonary complications in childhood: A retrospective study

INTRODUCTION

Incidence of severe M. pneumoniae pneumonia (SMPP) reported in China has been increasing over the last decade. We aimed to evaluate the clinical features of pediatric SMPP with pulmonary complications, according to laboratory tests and chest radiographic resolution patterns.

MATERIAL AND METHODS

We retrospectively reviewed 93 SMPP patients between January 2016 and February 2019, and grouped them by pneumonia pattern: pulmonary complications (63 patients) and extensive lung lesions without pulmonary complications (30 patients).

RESULTS

SMPP patients with pleural effusion (medium or large) and necrotizing pneumonia showed longer duration of fever, high serum value of lactate dehydrogenase (LDH), d-dimer, and LDH to albumin ratio (LAR). LAR and  d-dimer were associated with moderate or massive pleural effusion, and  d-dimer was associated with lung necrosis. The average time of radiographic resolution in the pulmonary complication group was 12 weeks, while those with elevated d-dimer were significantly more likely to have longer time for radiographic clearance.

CONCLUSION

We conclude that M. pneumoniae pneumonia in patients with pleural effusion (medium or large) or lung necrosis was more severe than those without pulmonary complications. LAR and  d-dimer might be used as parameters to identify children susceptible to pleural effusion (medium or large) or lung necrosis, and longer time for radiographic clearance among pediatric patients of SMPP.

Relationship between Atopic Disease and Acute Ocular and Systemic Outcomes in Patients with Stevens-Johnson Syndrome/Toxic Epidermal Necrolysis

OBJECTIVE

To describe the relationship between history of atopic disease on systemic and ocular manifestations of Stevens-Johnson Syndrome/Toxic Epidermal Necrolysis (SJS/TEN).

METHODS

Retrospective chart review of patients with SJS/TEN patients. Those with and without prior atopic diagnosis were compared.

RESULTS

In total, 200 patients with SJS/TEN were identified. A total of 23 patients also had an atopic diagnosis. Four, 10, and 18 had atopic dermatitis, allergic rhinitis, and asthma respectively. Acute ocular severity was significantly worse in the atopic cohort. No significant differences in overall systemic severity of SJS or mortality were found between the atopic and non-atopic cohorts. Compared to our hospital system's general population, prevalence of an atopic diagnosis was significantly higher in those with SJS/TEN.

CONCLUSION

Patients with a history of an atopic diagnosis appear to have more significant acute ocular involvement during their SJS/TEN hospitalization. Atopic conditions appear to occur more frequently in the SJS/TEN population compared to the general population.

Insight into the Pathogenic Mechanism of Mycoplasma pneumoniae

Mycoplasma pneumoniae, an obligate parasitic pathogen without cell wall, can cause severe upper and lower respiratory tract symptoms. It is the pathogen of human bronchitis and walking pneumonia, and named community-acquired pneumonia. In addition to severe respiratory symptoms, there are clinical extrapulmonary manifestations in the skin, brain, kidney, musculoskeletal, digestive system, and even blood system after M. pneumoniae infection. Hereby, we comprehensively summarized and reviewed the intrapulmonary and extrapulmonary pathogenesis of M. pneumoniae infection. The pathogenesis of related respiratory symptoms caused by M. pneumoniae is mainly adhesion damage, direct damage including nutrient predation, invasion and toxin, cytokine induced inflammation damage and immune evasion effect. The pathogenesis of extrapulmonary manifestations includes direct damage mediated by invasion and inflammatory factors, indirect damage caused by host immune response, and vascular occlusion. The intrapulmonary and extrapulmonary pathogenic mechanisms of M. pneumoniae infection are independent and interrelated, and have certain commonalities. In fact, the pathogenic mechanisms of M. pneumoniae are complicated, and the specific content is still not completely clear, further researches are necessary for determining the detailed pathogenesis of M. pneumoniae. This review can provide certain guidance for the effective prevention and treatment of M. pneumoniae infection.

The Diagnostic Value of High-Resolution Computed Tomography Features Combined with Mycoplasma Pneumoniae Ribonucleic Acid Load Detection for Refractory Mycoplasma Pneumonia

The aim of this study was to investigate the value of high-resolution computed tomography (CT) images and mycoplasma pneumoniae (MP) ribonucleic acid (RNA) load detection in the early diagnosis of refractory mycoplasma pneumoniae (RMP) and provide more methods for the diagnosis and treatment of RMP. Seventy children with MP were divided into the RMP group (H1 group, 31 cases) and the MP group (H2 group, 39 cases) according to pathological findings, and all of them underwent CT scanning. MP-RNA load and genotype distribution were analyzed in both groups, and the diagnostic efficacy of CT combined with MP-RNA load for RMP was calculated. The sensitivity of children in the H1 group to erythromycin (59.17% vs 71.56%) and clarithromycin (53.21% vs 67.03%) was lower than that in the H2 group, and the resistance rate of children in the H1 group to erythromycin (71.43% vs 67.53%) and clarithromycin (64.24% vs 50.37%) was higher than that in the H2 group (P < 0.05); the regression coefficients between lactate dehydrogenase (LDH) and the MPLI value of RMP were −0.064 and −0.413, respectively, which were significantly negatively correlated (P < 0.05); the accuracy (96.5%), sensitivity (92.5%), and specificity (88%) of CT + MP-RNA in the diagnosis of RMP were significantly higher than those of CT alone (91%, 88%, and 82%) and MP-RNA alone (88%, 84.5%, and 74%), which were significantly different (P < 0.05). The results of high MP-RNA load detection can be used as an indicator to predict RMP, and the diagnostic efficacy is significantly improved after combination with high-resolution CT, with high clinical application value.

Serum amyloid a, C-reactive protein, and procalcitonin levels in children with Mycoplasma pneumoniae infection

Background

Mycoplasma pneumoniae (MP) is a common pathogen of community‐acquired pneumonia in children. In the present study, serum amyloid A (SAA), C‐reactive protein (CRP), and procalcitonin (PCT) levels in children with MP infection were analyzed and the differential diagnoses of MP evaluated.

Methods

The study included 152 children with MP infection hospitalized in Tai’an Central Hospital in Shandong Province and 50 healthy children as controls. SAA, CRP, and PCT, as well as serum immunoglobulins and T lymphocyte subsets were analyzed during the acute and convalescent phases. Among the MP‐infected children, 30 cases were selected to monitor the SAA, immunoglobulins, and T lymphocyte subset levels for a week.

Results

The SAA, CRP, PCT, IgA, and IgM levels were significantly higher in the MP‐infected group than in the control group (F_(SAA) = 83.91, p < 0.05; F_(CRP) = 40.79, p < 0.05; F_(PCT) = 60.58, p < 0.05; F_(IgA) = 43.45, p < 0.05; F_(IgM) = 233.88, p < 0.05). In addition, the levels of these factors were significantly higher in the acute phase than in the convalescent phase (p < 0.05). However, significant difference was not observed in the IgG level between these two groups (p > 0.05). The CD3⁺ and CD4⁺ levels in the MP‐infected group were lower than in the control group ( F_(CD3+)= 60.58, P < 0.05; F_(CD4+) = 89.05, p < 0.05), and the CD8⁺ level was higher than in the control group ( F_(CD8+)= 96.96, p < 0.05). The CD3⁺, CD4⁺, and CD8⁺ levels were significantly different between the acute phase and the convalescent phase (CD3⁺: acute phase vs. convalescent phase, q = 2.79, p < 0.05; CD4⁺: acute phase vs. convalescent phase, q = 2.83, p < 0.05; CD8⁺: acute phase vs. convalescent phase, q = 3.15, p < 0.05). The changes in serum SAA levels in the MP‐infected group positively correlated with the changes in IgA, IgM, and CD8⁺ levels and negatively correlated with CD3⁺, CD4⁺, and CD4⁺/CD8⁺.

Conclusion

SAA, CRP, and PCT were specific markers for diagnosing early MP infection in children. These findings are important in the differential diagnosis of MP infection and clinical guidance for MP treatment.

Characteristics of Lung Microbiota in Children's Refractory Mycoplasma pneumoniae Pneumonia Coinfected with Human Adenovirus B

Background

Both M. pneumoniae and human adenovirus (HAdV) are common causative agents of lower respiratory tract infection in children; nonetheless, the lung microbiota in patients with coinfection of HAdV and M. pneumoniae remain unexplored.

Methods

Thirty-two children, diagnosed with refractory M. pneumoniae pneumonia (RMPP), entered into the one-year study from July 1, 2019 to June 30, 2020. Among them, twenty-one entered into the M. pneumoniae monoinfection (MP) group and eleven entered into the M. pneumoniae and HAdV coinfection (MP&ADV) group. The characteristics of the clinical findings were examined, and the lung microbiota was analyzed by metagenomic next generation sequencing (mNGS).

Results

Eleven patients in the MP&ADV group were coinfected with human mastadenovirus species B. The fever days lasted for significantly longer periods in the MP&ADV group than in the MP group (P < 0.05). The percentage of CD16⁺CD56⁺ cells was significantly higher in the MP&ADV group than that in the MP group (P < 0.05). There were no significant differences in α-diversity between the MP and MP&ADV groups, but the β-diversity was clearly higher in the MP&ADV group than that in the MP group (P < 0.05). At the microbial level, the top phylum of the MP BALF microbiota was Tenericutes; in contrast, it was Preplasmiviricota in the MP&ADV BALF. There were significant differences in the relative abundance of Tenericutes and Preplasmiviricota between the two groups (P < 0.001). There was a strong positive correlation between human mastadenovirus B and fever days, M. pneumoniae and level of IgA, and a strong negative correlation between Mycoplasma pneumoniae and PCT.

Conclusions

In RMPP, the BALF microbiota in children with mono M. pneumoniae infection was simpler than those with coinfection with human mastadenovirus B. Prolonged fever days were associated with human mastadenovirus B coinfection.

Mycoplasma pneumoniae Infections and Primary Immune Deficiencies

Mycoplasma pneumoniae (M. pneumoniae) is one of the leading causes of community-acquired pneumonia in children and is also implicated in a variety of reactive extrapulmonary diseases. Recurrent and/or severe respiratory infections are one of the most frequent manifestations of several types of primary immunodeficiency. Here, we reviewed the medical literature to assess the potential relevance of M. pneumoniae in the infections observed in children affected with combined, humoral, and innate primary immune deficiencies. M. pneumoniae does not result to be epidemiologically prevalent as a cause of pneumonia in children affected by primary immunodeficiencies, but this infection can have a persistent or severe course in this category of patients. Indeed, the active search of M. pneumoniae could be useful and appropriate especially in children with humoral immune deficiencies. Indeed, most cases of M. pneumoniae infection in primary immunodeficiencies are described in patients affected by a/hypo-gammaglobulinemia.

Mycoplasma pneumoniae Seroprevalence and Total IgE Levels in Patients with Juvenile Idiopathic Arthritis

Background

Mycoplasma pneumoniae (M. pneumoniae) is implicated in several immune-mediated extrapulmonary manifestations, including reactive arthritis. Recently, increased total serum IgE were reported in children developing M. pneumoniae-related extrapulmonary diseases (MpEPDs). Here, we aimed at analyzing these aspects in children affected with rheumatic disorders and, in detail, Juvenile Idiopathic Arthritis (JIA).

Methods

M. pneumoniae serology (IgG and IgM) and total serum IgE were concomitantly analyzed in 139 pediatric patients diagnosed with: JIA (Group 1, n = 85), or any rheumatic disease other than JIA (Group 2, n = 27), or non-inflammatory endocrinological disorders (Group 3, n = 27).

Results

Overall, 19.4% M. pneumoniae seroprevalence was observed in this hospitalized pediatric population, without signicant differences among the three groups. No significant differences in total serum IgE levels were noted among these groups; however, a second analysis excluding children with very high (and clearly abnormal) IgE levels suggested that JIA patients and, in detail, those with oligopolyarticular forms may have higher serum IgE concentrations. This relative difference among groups in serum IgE level seems to be more pronounced in M. pneumoniae seropositive children.

Conclusions

M. pneumoniae infection should be actively sought in children developing immune-mediated diseases, including patients affected with JIA and, especially, in oligopolyarticular forms. There is some evidence that total serum IgE levels may tend to be increased in patients with oligopolyarticular JIA subtype and especially in those resulting as M. pneumoniae seropositive. However, further and focused research is needed to confirm these preliminary results and to clarify the relation between M. pneumoniae infection, atopic status, and immune-mediated arthritis.

Epidemiological characteristics, clinical characteristics, and prognostic factors of children with atopy hospitalised with adenovirus pneumonia

Background

Atopy may be associated with disease severity and a poor prognosis of human adenovirus (HAdV) pneumonia in children. Our aim was to observe the clinical characteristics and pulmonary radiological changes in children with atopy and HAdV pneumonia in China.

Methods

Children hospitalised with HAdV pneumonia from June 2018 to December 2019 were analysed. All children were divided into atopic with HAdV, non-atopic with HAdV, and atopic without HAdV infection group. Each group was further divided into the mild and severe pneumonia groups according to disease severity. Standard treatment was initiated after admission, and regular follow-up evaluations were conducted at 1 month after discharge. Baseline and clinical characteristics and pulmonary radiological changes in children with and without atopy were evaluated. Risk factors associated with small airway lesions in patients with HAdV pneumonia were analysed.

Results

The eosinophil count in the atopic group was significantly higher than that in the non-atopic group (P < 0.05). Severe coughing, wheezing, and small airway lesions on chest high-resolution computed tomography (HRCT) upon admission, after discharge and 1 month after discharge were significantly higher in the atopic group (with or without HAdV infection) than in the non-atopic group (P < 0.05). There were significant differences in the number of patients with wheezing and small airway lesions during hospitalisation and after discharge among the three groups (P < 0.05). The risks of small airway lesions in children with a family or personal history of asthma, severe infection, atopy, and HAdV infection were 2.1-, 2.7-, 1.9-, 2.1-, and 1.4-times higher than those in children without these characteristics, respectively.

Conclusions

Children with atopy and HAdV pneumonia may experience severe coughing in mild cases and wheezing in mild and severe cases. Children with atopy are more susceptible to the development of small airway lesions, recurrent wheezing after discharge and slower recovery of small airway lesions as observed on pulmonary imaging than non-atopic children after HAdV infection. A family or personal history of asthma, atopy, severe infection, and HAdV infection are independent risk factors associated with the development of small airway lesion as observed on chest HRCT.

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.

The Level of D-Dimer Is Positively Correlated With the Severity of Mycoplasma pneumoniae Pneumonia in Children

Objective

Mycoplasma pneumoniae pneumonia (MPP) is an important disease in children. Studies have demonstrated that the levels of D-dimer are elevated in some children with MPP, especially those with thrombotic complications. However, the potential association between MPP and D-dimer remains unclear. In our study, we sought to explore the relationship between the levels of plasma D-dimer and clinical characteristics of MPP patients.

Methods

Retrospective analysis was conducted on 356 patients who were hospitalized in our hospital for MPP between January 1, 2017, and December 31, 2019. According to the peak value of D-dimer, patients were divided into three groups: the normal group (D-dimer<0.55 mg/L), the mild-moderately elevated group (D-dimer 0.55–5.5 mg/L) and the severely elevated group (D-dimer >5.5 mg/L). The demographic and clinical information, radiological findings, laboratory data, and treatments of patients were compared among different groups.

Results

106 patients were in the normal group, 204 patients were in the mild-moderately elevated group, and 46 patients were in the severely elevated group. More severe clinical and radiographic manifestations, longer length of fever, hospital stay and antibiotic therapy duration, higher incidences of extra-pulmonary complications, refractory MPP (RMPP), severe MPP (SMPP) were found in the elevated group, when compared with the normal group (P<0.01). Meanwhile, we found that the percentage of neutrophil (N%) and CD₈⁺ lymphocyte (CD₈⁺%), C-reactive protein (CRP), lactate dehydrogenase (LDH), interleukin (IL)-6, IL-10, and interferon-gamma (IFN-γ) trended higher with increasing D-dimer, whereas the percentage of lymphocyte (L%) and prealbumin (PAB) trended lower (P<0.01). In addition, the proportions of patients requiring oxygen therapy, glucocorticoid, bronchoscopy, immunoglobulin use, thoracentesis, or ICU admission were significantly higher in the severely elevated group than those in the other two groups (P<0.01). Correlation analysis showed that N%, L%, CRP, LDH, IL-10, length of fever, length of stay, and length of antibiotic therapy had strong correlations with the level of D-dimer.

Conclusions

MPP patients with higher levels of D-dimer had more severe clinical manifestations and needed longer duration of treatment, which might be closely related to the severity of lung inflammation after MP infection.

Clinical Predictors of Wheezing Among Children Infected With Mycoplasma Pneumoniae

Background: Mycoplasma pneumoniae (MP) not only was a common pathogen of respiratory tract infections, but also could trigger the exacerbation of asthmatic symptoms in children with or without asthma. Objective: This study aimed to identify possible risk factors associated with wheezing among children diagnosed with MP infection. Methods: A retrospective analysis of medical records of children aged 28 days to 18 years old who visited the Shanghai Children's Hospital between January 2019 and January 2020 was carried out, and all children were then classified into three groups: two wheezing groups (with or without MP infection) and a non-wheezing group with MP infection. Information including patient's demographics, clinical features, laboratory data, and radiography findings was extracted from the electronic medical record system. Chest radiographs were reviewed independently by two board-certified, blinded pediatric radiologists. Results: A total of 1,512 patients were included in our study, and 21.9% of them belonged to the wheezing group without MP infection. Among 1,181 patients with MP infection, 295 people (25.0%) suffered from wheezing, and males accounted for 61%. Through the multivariable logistic regression analyses, we found that six variables were positively associated with wheezing attacks in children with MP infection: male gender (likelihood ratio [LR] = 2.124, 95% confidence interval [CI]: 1.478-3.053), history of allergy (LR= 3.301, 95% CI: 2.206-4.941), history of wheezing (LR = 7.808, 95% CI: 5.276-11.557), autumn in reference to summer (LR = 2.414, 95% CI: 1.500-3.885), non-end-point infiltration in reference to consolidation or pleural effusion (LR = 1.982, 95% CI: 1.348-2.914), and infiltration scope (LR = 1.773, 95% CI: 1.293-2.432). However, the model showed that the probability of wheezing after MP infection decreased as age increased (LR = 0.257, 95% CI: 0.196-0.337). Moreover, the area under the curve (AUC) of the regression model was as high as 0.901 (0.847-0.955). Conclusion: The model integrated with factors including gender, age, season, radiological patterns, infiltration scope, and history of allergy performed well in predicting wheezing attack after MP infection in children.

Immunological Features of Pediatric Interstitial Pneumonia Due to Mycoplasma pneumoniae

Background: Inflammatory response, oxidative stress, and immunologic mechanism are involved in the pathogenesis of Mycoplasma pneumoniae pneumonia (MPP). However, the role of immune system of pediatric interstitial pneumonia due to M. pneumoniae infections remains poorly understood. The aim of this study was to analyze the immunologic features of pediatric interstitial pneumonia due to Mycoplasma pneumoniae (M. pneumoniae). Methods: A retrospective study was conducted on a primary cohort of children with MPP. Propensity score analysis was performed to match interstitial pneumonia and pulmonary consolidation children. Results: The clinical characteristics strongly associated with the development of interstitial pneumonia were boys, age >5 years, wheezing history, hydrothorax free, lymphocytes (>3.0 × 10⁹/L), CD19⁺ (>0.9 × 10⁹/L), CD3⁺ (>2.5 × 10⁹/L), CD4⁺ (>1.5 × 10⁹/L), CD8⁺ (>0.9 × 10⁹/L), interleukin-6 (IL-6, <30 pg/ml), IL-10 (<6 pg/ml), and interferon-γ (IFN-γ, <15 pg/ml). After propensity score analysis, children with interstitial pneumonia showed significantly higher CD19⁺, CD3⁺, and CD4⁺ T cell counts, and lower serum IL-6, IL-10, and IFN-γ levels. The final regression model showed that only CD4⁺ T cells (>1.5 × 10⁹/L, OR = 2.473), IFN-γ (<15 pg/ml, OR = 2.250), and hydrothorax free (OR = 14.454) were correlated with the development of interstitial pneumonia among children with MPP. Conclusions: The M. pneumoniae-induced interstitial pneumonia showed increased CD4⁺ T cells and lower serum IFN-γ level. Specific immunologic profiles could be involved in the development of pediatric interstitial pneumonia due to M. pneumoniae infections.

Interleukin-23 derived from CD16+ monocytes drives IL-17 secretion by TLR4 pathway in children with mycoplasma pneumoniae pneumonia

AIMS

The study aimed to investigate whether IL-23 is amplified in monocyte subsets of MP pneumonia and to determine its relevant pathway.

MATERIALS AND METHODS

We firstly analyze the IL-23p19 expression in monocyte subgroups in MP pneumonia patients and healthy controls subjects by using flow cytometry. Then, we also analyzed the percentage of IL-17⁺γδT cells and Th17 cells in patients with MP pneumonia and controls subjects. At the same time, the relation between IL-23 and IL-17 were also assessed. Furthermore, we constructed the recombinant community-acquired respiratory distress syndrome (CARDS) toxin and intend to stimulate peripheral blood mononuclear cells and RAW264.7 cells in vitro. IL-23p19 was detected by flow cytometry and the mRNA levels were measured by real-time PCR. Finally, TLR4 pathway was also investigated by TAK242 inhibitor.

KEY FINDINGS

It turned out that the expression of IL-23p19 was increased in CD14^brightCD16⁺ monocyte of MP pneumonia patients than controls subjects. The patients with MP pneumonia had significantly higher the percentage of IL-17⁺γδT cells and Th17 cells than controls subjects. Interestingly, the levels of IL-23 were positively related to IL-17 in MP pneumonia patients. CD16⁺ monocytes and RAW264.7 cells, respectively can be induced by CARDS toxin to secrete IL-23 by TLR4 pathway in vitro.

SIGNIFICANCE

These results indicated that IL-23-IL-17⁺γδT/Th17 axis may play a role in the pathogenesis of MP pneumonia, whereas IL-23 derived from CD16⁺ monocytes was expanded in MP pneumonia by TLR4 pathway.

Serum Cytokines and FeNO in School-Aged Children with Mycoplasma pneumoniae Pneumonia

Background

Mycoplasma pneumoniae is a major cause of community-acquired pneumonia (CAP) that is particularly prevalent in school-aged children. This study explored the potential involvement of cytokines in children with Mycoplasma pneumoniae pneumonia (MPP) infection.

Material/Methods

Children aged 3–7 years who were hospitalized due to CAP infection were enrolled and divided into 2 groups: an MPP group (n=33) and a NMPP group (n=38), along with 21 age-matched healthy controls. Clinical characteristics and laboratory data were recorded. Serum levels of IL-18, IL-33, IFN-γ, IL-5, IL-6, IL-8, and IL-13 were assessed using Luminex xMAP technology. Correlation analysis and ROC curves analysis were also performed to further explore the role of these detected cytokines in CAP.

Results

Compared with the healthy controls, the serum expression of IL-18, IL-33, IFN-γ, IL-5, IL-6, IL-8, and IL-13 were significantly higher in the MPP and NMPP groups. Furthermore, serum IL-18 expression was found to be significantly correlated with lgE, FeNO, IL-5, IL-8, and IL-13 concentrations. Significant differences were also observed between the MPP group and NMPP group patients in levels of IL-18, IL-5, and IL-6, and further ROC analysis showed that the area under the curve (AUC) of IL-18 and IL-5 were 0.813 (95% CI: 0.710–0.917; P<0.01) and 0.844 (95% CI: 0.756–0.933; P<0.01), respectively.

Conclusions

IL-18, IL-33, IFN-γ, IL-5, IL-6, IL-8, and IL-13 serum levels showed significant differences in children with CAP. IL-18 and IL-5 were much higher in the MPP group compared to the NMPP group patients, whereas IL-6 levels were significantly lower in these 2 groups.

Monocyte subsets study in children with Mycoplasma pneumoniae pneumonia

The aim of this study was to evaluate the changes in the three subsets of monocyte (classical, intermediate, and non-classical) and the expression of human leukocyte antigen-DR (HLA-DR) on monocyte subsets during MP pneumonia in children. Monocyte subsets were analyzed in the peripheral blood of healthy volunteers and MP pneumonia patients at the stages of admission and remission after clinical therapy. They were defined as classical (CD14⁺CD16^-), intermediate (CD14^brightCD16⁺), and non-classical (CD14^dimCD16⁺) using flow cytometry. Furthermore, three subsets of monocyte were analyzed for the expression of HLA-DR. Patients with MP pneumonia at admission had a higher proportion of intermediate and non-classical monocytes than healthy subjects (all P < 0.05). The proportion of intermediate subset and non-classical subset was lower in MP pneumonia patients at remission than at admission (all P < 0.05). In comparison with the other monocyte subsets, intermediate subset showed a significantly higher percentage of HLA-DR in MP pneumonia patients at admission (P < 0.05). Further analysis revealed that the expression of HLA-DR on intermediate subset was lower in severe patients than in non-severe patients (P < 0.05).Our data has shown for the first time that MP pneumonia is associated with the increased proportion of non-classical and intermediate monocytes, indicating the involvement of monocyte-related mechanisms in the pathogenesis of this disease. Additionally, the decreased expression of HLA-DR on CD14^brightCD16⁺ subset may be a potential indicator of the severity of MP pneumonia.

Impact of atopy on the severity and extrapulmonary manifestations of childhood Mycoplasma pneumoniae pneumonia

Objectives

The impact of atopy on disease severity and extrapulmonary manifestations in children with Mycoplasmapneumoniae (MP) pneumonia is unknown.

Methods

Patients diagnosed with MP pneumonia between January 2016, and December 2017, were enrolled in this study. A total of 150 MP pneumonia patients were enrolled at diagnosis and divided into the atopic group (n = 48) and the nonatopic group (n = 102). Furthermore, these patients were also assessed after being divided into the pulmonary group (n = 120) and the extrapulmonary group (n = 30). Clinical characteristics, respiratory disease severity, any allergy history, and specific allergen sensitizations were collected from all patients. The serum interleukin‐17 (IL‐17) and total immunoglobulin E (lgE) levels were also measured.

Results

More children in the atopic group than those in the nonatopic group presented with severe MP pneumonia, tachypnea, oxygen therapy, steroid treatment, atopic conditions including asthma attack, a previous history of asthma, decreased IL‐17 levels, and increased IgE levels (all P < 0.05). When compared with those in the pulmonary group, the patients in the extrapulmonary group showed higher percentages of atopy, higher total lgE levels, and lower IL‐17 levels (all P < 0.05).

Conclusions

Atopy may be a risk factor for disease severity and extrapulmonary manifestations in children with MP pneumonia.