The upper-airway microbiota and loss of asthma control among asthmatic children

Relationship between pediatric asthma and respiratory microbiota, intestinal microbiota: a narrative review

Pediatric asthma is a common chronic airway inflammatory disease that begins in childhood and its impact persists throughout all age stages of patients. With the continuous progress of detection technologies, numerous studies have firmly demonstrated that gut microbiota and respiratory microbiota are closely related to the occurrence and development of asthma, and related research is increasing day by day. This article elaborates in detail on the characteristics, composition of normal gut microbiota and lung microbiota at different ages and in different sites, as well as the connection of the gut-lung axis. Subsequently, it deeply analyzes various factors influencing microbiota colonization, including host factor, delivery mode, maternal dietary and infant feeding patterns, environmental microbial exposure and pollutants, and the use of antibiotics in early life. These factors are highly likely to play a crucial role in the onset process and disease progression of asthma. Research shows that obvious changes have occurred in the respiratory and gut microbiota of asthma patients, and these microbiomes exhibit different characteristics according to the phenotypes and endotypes of asthma. Finally, the article summarizes the microbiota-related treatment approaches for asthma carried out in recent years, including the application of probiotics, nutritional interventions, and fecal microbiota transplantation. These treatment modalities are expected to become new directions for future asthma treatment and bring new hope for solving the problem of childhood asthma.

Oral microbiota related to allergy in Norwegian adults

Background

Oral microbiome composition has been linked to onset and progression of several localized and systemic diseases. Associations with allergy in adults have been less explored.

Objective

We sought to identify oral microbiota associated with allergy outcomes in adults using high-throughput sequencing data.

Methods

We characterized bacterial communities of gingival samples from 453 Norwegian adults (average age, 28 years) using 16S rRNA gene amplicon sequencing. We examined more than 2200 bacterial taxa in relation to self-reported current asthma, eczema, or rhinitis, and seroatopy (IgE > 0.70 kU/L). We used linear regression to determine whether overall bacterial diversity differed by each allergic outcome and analysis of composition of microbiomes with bias correction (ANCOM-BC2) to identify differentially abundant taxa.

Results

Less diverse oral bacterial communities were observed (P < .05) in individuals with atopy or rhinitis compared with those without. Bacterial diversity did not differ by asthma and eczema status. While no bacterial taxa were differentially abundant by asthma, many were differentially abundant (P < .05 after multiple-testing correction) in relation to atopy, eczema, and rhinitis. These taxa include several from the genera Leptotrichia and Fusobacterium. Some, including Streptococcus, were previously implicated in respiratory health, whereas others were novel. We also found taxa related to nasal medication use in individuals with rhinitis. Notably, microbial network interconnections differed by allergy status.

Conclusions

Bacterial community compositions of oral gingival samples may play a role in allergic outcomes in adults. These findings could contribute to the development of novel treatment strategies.

Associations of ambient fine particulate matter with lung function and nasal microbiota: A panel study in asthmatic children

Fine particulate matter (PM2.5) has been associated with an increased risk of asthma. However, the underlying mechanisms through which PM2.5 affects respiratory health in children with asthma remain poorly understood. To address this gap, we performed a panel study to investigate the associations of short-term PM2.5 exposure with lung function and nasal microbiota in asthmatic children. The study included 50 school-aged asthmatic children, who underwent repeated examinations every three months, including lung function testing and nasal swab sample collection. Linear mixed-effect models and the linear discriminant analysis effect size were adopted to evaluate the impacts of PM2.5 on lung function and nasal microbiota. Based on 160 lung function records and 160 nasal samples, we found that per interquartile range increase in PM2.5 concentration at lag 0-72 h was associated with a decrease of 0.09 L (95 % CI: 0.01, 0.16), 0.30 L/s (95 CI: 0.04, 0.57), 0.18 L/s (95 % CI: 0.03, 0.33), and 0.30 L/s (95 % CI: 0.07, 0.53) in forced expiratory volume in 1 s, forced expiratory flow at 50 % and 75 % of forced vital capacity, and the maximal mid-expiratory flow, respectively. Additionally, short-term exposure to PM2.5 was also associated with decreased Chao 1 and Simpson's index, decreased relative abundance in Corynebacterium and Staphylococcus, and increased relative abundance in Muribaculaceae, Ralstonia, and Moraxella. In conclusion, our study demonstrated that short-term exposure to PM2.5 may impair small airway function, reduce nasal microbiota evenness, and induce microbiota dysbiosis in asthmatic children.

Investigation of dynamic microbial migration patterns in the respiratory tract

Background

The role of the respiratory microbiome in lung diseases is increasingly recognized, with the potential migration of respiratory pathogens being a significant clinical consideration. Despite its importance, evidence elucidating this phenomenon remains scarce.

Methods

This prospective study collected clinical samples from patients with suspected lower respiratory tract infections (LRTI), including oropharyngeal swabs (OPS), sputum, and bronchoalveolar lavage fluid (BALF). Metagenomic next-generation sequencing (mNGS) was employed to analyze respiratory microbial diversity, complemented by Bayesian source tracking and sequence alignment analyses to explore pathogen migration patterns.

Results

A cohort of 68 patients was enrolled, with 56 diagnosed with LRTI and 12 with non-infectious respiratory conditions. A statistically significant disparity in respiratory microbiome diversity was observed between infected and non-infected groups (p < 0.05). Intriguingly, no significant variations in microbial community structure, including alpha and beta diversity, were detected across different respiratory tract sites within individuals. The Bayesian source tracking analysis revealed a pronounced migration pattern among pathogens compared to the overall microbial community, with migration ratios of 51.54% and 1.92%, respectively (p < 0.05). Sequence similarity analysis further corroborated these findings, highlighting a notable homology among specific migrating pathogens.

Conclusion

This study represents a pioneering effort in deducing pathogen migration patterns through microbial source tracking analysis. The findings provide novel insights that could significantly advance clinical diagnostics and therapeutic strategies for respiratory infections.

The global burden and trends of asthma from 1990 to 2021, and its changes during the COVID-19 pandemic: An observational study

OBJECTIVES

This study aims to comprehensively analyze the global burden and trends of asthma, along with their variations during the COVID-19 pandemic.

STUDY DESIGN

An observational study.

METHODS

The data on age-standardized rates of incidence (ASIR), prevalence (ASPR), and deaths (ASDR) for asthma were accessed from the Global Burden of Disease 2021. Estimated annual percentage changes (EAPCs) and annual percent changes (APCs) were calculated to describe secular trends. The rate differences between the average rates of 2020-2021 and those of 2018-2019 represent the change in the burden of asthma before and during the COVID-19 pandemic.

RESULTS

In 2021, the global ASIR, ASPR, and ASDR of asthma were 516.70, 3340.12, and 5.2 per 100,000, with EAPCs of -1.04 %, -1.59 %, and -2.03 %, respectively. However, from 2018 to 2021, the global ASIR and ASPR of asthma showed a significant upward trend, with APCs of 0.41 % (95 % CI: 0.11 %-0.86 %) and 0.28 % (95 % CI: 0.04 %-0.69 %), respectively. During the COVID-19 pandemic, the global ASIR and ASPR increased significantly (rate differences were 5.26 and 23.10 per 100,000, respectively), especially in the high SDI regions (rate differences were 16.28 and 51.05 per 100,000, respectively), and among children aged under 5 (rate differences were 12.73 and 82.09 per 100,000, respectively).

CONCLUSION

During the COVID-19 pandemic period in 2020-2021, the incidence and prevalence of asthma have exhibited an upward trend globally, especially in high SDI regions and among children under 5 years old. This necessitates increased attention and intervention.

Perturbations in the airway microbiome are associated with type 2 asthma phenotype and severity

BACKGROUND

Airway microbiome has been linked to asthma heterogeneity, yet little is known about the associations between airway microbiota and type 2 (T2) asthma phenotype and severity.

OBJECTIVE

To determine the relationship of nasopharyngeal (NP) and induced sputum (IS) microbiota to the phenotypic features of T2 asthma.

METHODS

NP and IS samples from subjects with T2 mild-to-moderate asthma (n = 23), subjects with severe asthma (n = 21), and healthy controls (n = 16) were analyzed. Bacterial microbiota and functional profiles were compared. The correlation between microbial communities and clinical and inflammatory features was evaluated in individuals with asthma of 2 statuses.

RESULTS

Differences in NP and IS microbiota were associated with T2 asthma phenotype. Alterations in NP microbiota were more reflective of T2 inflammation and severity, with additional stratification of a subgroup characterized by significant elevations in T2 inflammatory biomarkers and reductions in bacterial richness and diversity (P < .05). Burkholderia-Caballeronia-Paraburkholderia, Ralstonia, and Rhodococcus were identified as hub taxa within NP microbial network in T2 severe asthma, which were prevalent in the entire airway and involved in bacterial functions including inflammatory and steroid responses (P < .05). The composition and diversity of IS microbiota were complex, with Veillonella as the most altered genus, having an increase with increasing asthma severity.

CONCLUSION

Our work revealed the significant associations of microbiota perturbations throughout the entire respiratory tract to the extent of T2 inflammation, phenotype and severity in T2 asthma. The specific taxa identified invite further mechanistic investigations to unravel their possibility as biomarkers and therapeutic targets for T2 severe asthma.

The Microbiome in Asthma Heterogeneity: The Role of Multi-Omic Investigations

Asthma is one of the most prevalent and extensively studied chronic respiratory conditions, yet the heterogeneity of asthma remains biologically puzzling. Established factors like exogenous exposures and treatment adherence contribute to variability in asthma risk and clinical outcomes. It is also clear that the endogenous factors of genetics and immune system response patterns play key roles in asthma. Despite significant existing knowledge in the above, divergent clinical trajectories and outcomes are still observed, even among individuals with similar risk profiles, biomarkers, and optimal medical management. This suggests uncaptured biological interactions that contribute to asthma's heterogeneity, for which the role of host microbiota has lately attracted much research attention. This review will highlight recent evidence in this area, focusing on bedside-to-bench investigations that have leveraged omic technologies to uncover microbiome links to asthma outcomes and immunobiology. Studies centered on the respiratory system and the use of multi-omics are noted in particular. These represent a new generation of reverse-translational investigations revealing potential functional crosstalk in host microbiomes that may drive phenotypic heterogeneity in chronic diseases like asthma. Multi-omic data offer a wide lens into ecosystem interactions within a host. This informs new hypotheses and experimental work to elucidate mechanistic pathways for unresolved asthma endotypes. Further incorporation of multi-omics into patient-centered investigations can yield new insights that hopefully lead to even more precise, microbiome-informed strategies to reduce asthma burden.

Association between allergic diseases and mental health conditions: An umbrella review

BACKGROUND

The mental health conditions of allergic diseases have been investigated, but the consistency and magnitude of their effects are unclear. The aim of this umbrella review was to systematically evaluate the published evidence on allergic diseases and mental health conditions to establish a new hierarchy of evidence and identify gaps in this area of research.

METHODS

We systematically searched PubMed, Embase, Web of Science, and the Cochrane Database of Systematic Reviews from database inception to April 30, 2024. We included systematic reviews that conducted meta-analyses that examined the association of allergic diseases and mental health conditions. We calculated summary effect estimates (odds ratios), 95% confidence intervals, I2 statistics, 95% prediction intervals, small study effects, and excess significance biases. We used AMSTAR 2 (A Measurement Tool to Assess Systematic Reviews 2) to appraise the methodologic quality of the included studies.

RESULTS

We identified 21 eligible articles, which yielded 37 associations (348,405,029 total population) of allergic diseases and mental health conditions. The credibility of evidence was convincing (class I) for asthma and risk of attention-deficit/hyperactivity disorder (odds ratio 1.34, 95% confidence interval 1.24-1.44); and highly suggestive (class II) for allergic rhinitis and risk of tic disorders (2.61, 1.90-3.57), allergic rhinitis and risk of sleep disorders (2.17, 1.87-2.53), food allergy and risk of autism spectrum disorder (2.79, 2.08-3.75), atopic dermatitis and risk of depression (1.60, 1.43-1.79), atopic dermatitis and risk of anxiety (1.62 1.42-1.85), atopic dermatitis and risk of attention-deficit/hyperactivity disorder (1.28, 1.18-1.40), atopic dermatitis and risk of suicidal ideation (1.44, 1.25-1.65), asthma and risk of depression (1.64, 1.50-1.78), asthma and risk of anxiety (1.95, 1.68-2.26), asthma and risk of tic disorders (1.90, 1.57-2.30), asthma and risk of suicidal ideation (1.52, 1.37-1.70), and asthma and risk of suicide attempts (1.60, 1.33-1.92).

CONCLUSIONS

Allergic diseases are associated with increased risk of a range of mental health conditions, with the most convincing evidence for asthma. However, these associations do not imply causality, and there is large heterogeneity in these associations, which requires high-quality primary studies to identify causality and strength of evidence.

Post-viral lung diseases: the microbiota as a key player

Viral infections of the respiratory tract can lead to chronic lung injury through immunopathological mechanisms that remain unclear. Communities of commensal bacteria colonising the respiratory tract, known as the respiratory tract microbiota, are altered in viral infections, which can contribute to inflammation, lung epithelial damage and subsequent development of lung disease. Emerging evidence on post-viral lung injury suggests an interplay between viral infections, immune responses and airway microbiota composition in the development of viral-induced lung diseases. In this review, we present the clinical characteristics of post-viral lung injury, along with the underlying immunopathological mechanisms and host-bacteria interactions, with a focus on influenza virus, respiratory syncytial virus and coronaviruses. Additionally, considering the important role of the airway microbiota in viral-induced pulmonary sequelae, we suggest key areas for future research on respiratory microbiota involvement in the development of post-viral lung diseases.

Computational and in vitro evaluation of probiotic treatments for nasal Staphylococcus aureus decolonization

Despite the rising challenge of antibiotic resistance, current approaches to eradicate nasal pathobionts Staphylococcus aureus and Streptococcus pneumoniae rely on antibacterials. An alternative is the artificial inoculation of commensal bacteria, i.e., probiotic treatment, supported by the increasing evidence for commensal-mediated inhibition of pathogens. To systematically investigate the potential of this approach, we developed a quantitative framework simulating the nasal microbiome dynamics by combining mathematical modeling with longitudinal microbiota data. By inferring community parameters using 16S ribosomal RNA (rRNA) amplicon sequencing data and simulating the nasal microbial dynamics of patients colonized with S. aureus, we compared the decolonization performance of probiotic and antibiotic treatments under different assumptions on patients' community composition and susceptibility profile. To further compare the robustness of these treatments, we simulated an S. aureus challenge and quantified the recolonization probability. Through in vitro experiments using nasal swabs of adults colonized with S. aureus, we confirmed that after antibiotic treatment, recolonization of S. aureus was inhibited in samples treated with a probiotic mixture compared to the nontreated control. Our results suggest that probiotic treatment outperforms antibiotics in terms of decolonization performance, recolonization robustness, and leads to less collateral reduction in the microbiome diversity. Thus, probiotic treatment may provide a promising alternative to combat antibiotic resistance, with the additional advantage of personalized treatment options via using the patient's own metagenomic data. The combination of an in silico framework with in vitro experiments using clinical samples reported in this work is an important step forward to further investigate this alternative in clinical trials.

Microbial influencers: the airway microbiome's role in asthma

Asthma is a common chronic respiratory disease affecting people of all ages globally. The airway hosts diverse microbial communities increasingly recognized as influential in the development and disease course of asthma. Here, we review recent findings on the airway microbiome in asthma. As relationships between the airway microbiome and respiratory health take root early in life, we first provide an overview of the early-life airway microbiome and asthma development, where multiple cohort studies have identified bacterial genera in the infant airway associated with risk of future wheeze and asthma. We then address current understandings of interactions between environmental factors, the airway microbiome, and asthma, including the effects of rural/urban environments, pet ownership, smoking, viral illness, and antibiotics. Next, we delve into what has been observed about the airway microbiome and asthma phenotypes and endotypes, as airway microbiota have been associated with asthma control, severity, obesity-related asthma, and treatment effects as well as with type 2 high, type 2 low, and more newly described multi-omic asthma endotypes. We then discuss emerging approaches to shape the microbiome for asthma therapy and conclude the Review with perspectives on future research directions.

Precision medicine for asthma treatment: Unlocking the potential of the epigenome and microbiome

Asthma is a leading worldwide biomedical concern. Patients can experience life-threatening worsening episodes (exacerbations) usually controlled by anti-inflammatory and bronchodilator drugs. However, substantial heterogeneity in treatment response exists, and a subset of patients with unresolved asthma carry the major burden of this disease. The study of the epigenome and microbiome might bridge the gap between human genetics and environmental exposure to partially explain the heterogeneity in drug response. This review aims to provide a critical examination of the existing literature on the microbiome and epigenetic studies examining associations with asthma treatments and drug response, highlight convergent pathways, address current challenges, and offer future perspectives. Current epigenetic and microbiome studies have shown the bilateral relationship between asthma pharmacologic interventions and the human epigenome and microbiome. These studies, focusing on corticosteroids and to a lesser extent on bronchodilators, azithromycin, immunotherapy, and mepolizumab, have improved the understanding of the molecular basis of treatment response and identified promising biomarkers for drug response prediction. Immune and inflammatory pathways (eg, IL-2, TNF-α, NF-κB, and C/EBPs) underlie microbiome-epigenetic associations with asthma treatment, representing potential therapeutic pathways to be targeted. A comprehensive evaluation of these omics biomarkers could significantly contribute to precision medicine and new therapeutic target discovery.

Early-life upper airway microbiota are associated with decreased lower respiratory tract infections

BACKGROUND

Microbial interactions mediating colonization resistance play key roles within the human microbiome, shaping susceptibility to infection from birth. The role of the nasal and oral microbiome in the context of early life respiratory infections and subsequent allergic disease risk remains understudied.

OBJECTIVES

Our aim was to gain insight into microbiome-mediated defenses and respiratory pathogen colonization dynamics within the upper respiratory tract during infancy.

METHODS

We performed shotgun metagenomic sequencing of nasal (n = 229) and oral (n = 210) microbiomes from our Wisconsin Infant Study Cohort at age 24 months and examined the influence of participant demographics and exposure history on microbiome composition. Detection of viral and bacterial respiratory pathogens by RT-PCR and culture-based studies with antibiotic susceptibility testing, respectively, to assess pathogen carriage was performed. Functional bioassays were used to evaluate pathogen inhibition by respiratory tract commensals.

RESULTS

Participants with early-life lower respiratory tract infection were more likely to be formula fed, attend day care, and experience wheezing. Composition of the nasal, but not oral, microbiome associated with prior lower respiratory tract infection, namely lower alpha diversity, depletion of Prevotella, and enrichment of Moraxella catarrhalis including drug-resistant strains. Prevotella originating from healthy microbiomes had higher biosynthetic gene cluster abundance and exhibited contact-independent inhibition of M catarrhalis.

CONCLUSIONS

These results suggest interbacterial competition affects nasal pathogen colonization. This work advances understanding of protective host-microbe interactions occurring in airway microbiomes that alter infection susceptibility in early life.

Respiratory Flora Intervention: A New Strategy for the Prevention and Treatment of Occupationally Related Respiratory Allergy in Healthcare Workers

Occupational allergic respiratory disease in healthcare workers due to occupational exposure has received widespread attention. At the same time, evidence of altered respiratory flora associated with the development of allergy has been found in relevant epidemiologic studies. It is of concern that the composition of nasopharyngeal flora in healthcare workers differs significantly from that of non-healthcare workers due to occupational factors, with a particularly high prevalence of carriage of pathogenic and drug-resistant bacteria. Recent studies have found that interventions with upper respiratory tract probiotics can significantly reduce the incidence of respiratory allergies and infections. We searched PubMed and other databases to describe the burden of allergic respiratory disease and altered respiratory flora in healthcare workers in this narrative review, and we summarize the mechanisms and current state of clinical research on the use of flora interventions to ameliorate respiratory allergy, with the aim of providing a new direction for protecting the respiratory health of healthcare workers.

The Impact of Adverse Childhood Experiences on Asthma Severity in US Adults

Background/objectives: The association between adverse childhood experiences (ACEs) and asthma severity among United States (US) adults with asthma has not been well documented. In addition, whether gender differences exist in this association has been underexplored. We aimed to examine the prevalence of asthma severity in the US adult population with asthma and investigate the association between ACEs and asthma severity by using data from non-institutionalized US adults with asthma. Methods: This cross-sectional study used data from the Adult 2019 and 2020 Behavioral Risk Factor Surveillance System (BRFSS) Asthma Call-Back Survey (ACBS), a survey of US adults aged 18 years or older in 31 US states and Puerto Rico. A total of 22934 adults with asthma participated in 2019 and 2020 ACBS. The 11 BRFSS ACE variables encompassing abuse and household dysfunction were used as ACE measures. ACE measures were summed up as cumulative ACE scores (continuous) and categorized (zero, one ACE, two ACEs, ≥ three ACEs). Asthma severity was categorized as intermittent or persistent. Weighted logistic regression models were used to assess associations of the cumulative ACE score, categorical ACE measures, and the 11 individual ACE responses with asthma severity controlling confounders. Gender differences were explored by stratifying by gender. Results: The prevalence of persistent asthma among US adults with asthma was 45.3%. The mean cumulative ACE score in adults with intermittent vs. persistent asthma was (2.43 vs. 2.70, p-value < 0.05). About 22% of adults with asthma had no ACEs, 19% had one ACE, 14% had two ACEs, and 45% had three or more ACEs. A one-unit increase in ACEs score was associated with a 5.4% increase in the odds of persistent asthma (adjusted odds ratio, aOR = 1.054 (95% confidence interval, CI = 1.01-1.10). Experiencing ≥ three ACEs compared to no ACEs was associated with 31% increased odds of persistent asthma (aOR = 1.31, 95% CI = 1.01-1.70). Individual ACE items significantly associated with persistent asthma include parent/adult ever touched you sexually (aOR = 1.33, 95% CI = 1.03-1.74), adult tried to make you touch them (aOR = 1.34, 95% CI = 1.01-1.79), any adult forced you to have sex (aOR = 1.44, 95% CI = 1.04-1.20), parental separation/divorce (aOR = 1.31, 95% CI = 1.05-1.63), and household alcohol abuse (aOR = 1.24, 95% CI = 1.01-1.53). In women, experiencing one ACE and ≥ three ACEs (compared to no ACEs) was associated with 51% and 60% increased odds of persistent asthma, respectively (aOR = 1.51, 95% CI = 1.02-2.23; aOR = 1.60, 95% CI = 1.12-2.27). No significant association was observed between ACEs and asthma severity in men; however, experiencing household physical violence (compared to no household physical violence) was associated with persistent asthma in men (aOR = 1.69, 95% CI = 1.18-2.42). Conclusions: In this cross-sectional study of US adults with asthma, exposure to ACEs was associated with higher odds of asthma overall and in women. These findings highlight the importance of preventive strategies and early interventions to reduce ACEs, potentially mitigating asthma's severity in adulthood.

[Changes in intestinal flora associated with childhood sleep-disordered breathing and the pathogenesis of non-alcoholic fatty liver disease in children]

Objective:To explore the interaction between pediatric sleep-disordered breathing（SDB）, the intestinal microbiota, and pediatric non-alcoholic fatty liver disease（NAFLD）. Methods:A total of 63 non-obese children（47 children with SDB in the experimental group and 16 without SDB in the control group） were enrolled in this study. The liver function and degree of SDB were assessed in both groups. High-throughput 16S rRNA sequencing was conducted to detect the composition and functional variations of the intestinal microbiota in the two groups of children. Results:Compared with children in the experimental group, serum ALT and AST levels were higher in the control group. and the relative proteobacteria abundance of intestinal flora increased, and the relative abundance of Bacteroidetes decreased significantly. Function including membrane transport, carbohydrate metabolism and lipid metabolism, were enriched in the intestinal microbiota of children with SDB. Conclusion:The composition and functional annotation of the pediatric liver functional status and gut microbiota were significantly different between the two groups of children with and without SDB. Changes in SDB-associated intestinal bacterial abundance may be related to the pathogenesis of pediatric NAFLD.

Species-level, metagenomic and proteomic analysis of microbe-immune interactions in severe asthma

BACKGROUND

The airway microbiome in severe asthma has not been characterised at species-level by metagenomic sequencing, nor have the relationships between specific species and mucosal immune responses in 'type-2 low', neutrophilic asthma been defined. We performed an integrated species-level metagenomic data with inflammatory mediators to characterise prevalence of dominant potentially pathogenic organisms and host immune responses.

METHODS

Sputum and nasal lavage samples were analysed using long-read metagenomic sequencing with Nanopore and qPCR in two cross-sectional adult severe asthma cohorts, Wessex (n = 66) and Oxford (n = 30). We integrated species-level data with clinical parameters and 39 selected airway proteins measured by immunoassay and O-link.

RESULTS

The sputum microbiome in health and mild asthma displayed comparable microbial diversity. By contrast, 23% (19/81) of severe asthma microbiomes were dominated by a single respiratory pathogen, namely H. influenzae (n = 10), M. catarrhalis (n = 4), S. pneumoniae (n = 4) and P. aeruginosa (n = 1). Neutrophilic asthma was associated with H. influenzae, M. catarrhalis, S. pneumoniae and T. whipplei with elevated type-1 cytokines and proteases; eosinophilic asthma with higher M. catarrhalis, but lower H. influenzae, and S. pneumoniae abundance. H. influenzae load correlated with Eosinophil Cationic Protein, elastase and IL-10. R. mucilaginosa associated positively with IL-6 and negatively with FGF. Bayesian network analysis also revealed close and distinct relationships of H. influenzae and M. catarrhalis with type-1 airway inflammation. The microbiomes and cytokine milieu were distinct between upper and lower airways.

CONCLUSIONS

This species-level integrated analysis reveals central, but distinct associations between potentially pathogenic bacteria and airways inflammation in severe asthma.

Airway bacterial microbiome signatures correlate with occupational pneumoconiosis progression

Recent evidence has pinpointed a key role of the microbiome in human respiratory health and disease. However, significant knowledge gaps still exist regarding the connection between bacterial communities and adverse effects caused by particulate matters (PMs). Here, we characterized the bacterial microbiome along different airway sites in occupational pneumoconiosis (OP) patients. The sequencing data revealed that OP patients exhibited distinct dysbiosis in the composition and function of the respiratory microbiota. To different extents, there was an overall increase in the colonization of microbiota, such as Streptococcus, implying a possible intrusion pathway provided by exogenous PMs. Compared to those of healthy subjects, unhealthy living habits (i.e., smoking) had a greater impact on microbiome changes in OP patients. Importantly, the associations between the bacterial community and disease indicators indicated that specific bacterial species, including Prevotella, Actinobacillus, and Leptotrichia, might be surrogate markers of OP disease progression. Collectively, our results highlighted the potential participation of the bacterial microbiota in the pathogenesis of respiratory diseases and helped in the discovery of microbiome-based diagnostics for PM-induced disorders.

Gut microbiota dysbiosis and its impact on asthma and other lung diseases: potential therapeutic approaches

The emerging field of gut-lung axis research has revealed a complex interplay between the gut microbiota and respiratory health, particularly in asthma. This review comprehensively explored the intricate relationship between these two systems, focusing on their influence on immune responses, inflammation, and the pathogenesis of respiratory diseases. Recent studies have demonstrated that gut microbiota dysbiosis can contribute to asthma onset and exacerbation, prompting investigations into therapeutic strategies to correct this imbalance. Probiotics and prebiotics, known for their ability to modulate gut microbial compositions, were discussed as potential interventions to restore immune homeostasis. The impact of antibiotics and metabolites, including short-chain fatty acids produced by the gut microbiota, on immune regulation was examined. Fecal microbiota transplantation has shown promise in various diseases, but its role in respiratory disorders is not established. Innovative approaches, including mucus transplants, inhaled probiotics, and microencapsulation strategies, have been proposed as novel therapeutic avenues. Despite challenges, including the sophisticated adaptability of microbial communities and the need for mechanistic clarity, the potential for microbiota-based interventions is considerable. Collaboration between researchers, clinicians, and other experts is essential to unravel the complexities of the gut-lung axis, paving a way for innovative strategies that could transform the management of respiratory diseases.

Assessment of the gut microbiota of children with obstructive sleep apnea syndrome: A systematic review

Sleep-disordered breathing promotes not only unfavorable craniofacial changes in untreated pediatric patients but also neurocognitive, metabolic, cardiovascular, and even long-term social alterations. This systematic review evaluated whether children diagnosed with obstructive sleep apnea syndrome (OSAS) have different intestinal microbiota constitutions from healthy children and was based on the PRISMA guidelines (PROSPERO: CRD42022360074). A total of 1562 clinical studies published between 2019 and 2023 were selected from the PubMed/MEDLINE, Embase, Web of Science, Scopus, and Cochrane Library databases, of which five were included in the qualitative analysis, three being randomized and two prospective. The methodological quality was assessed (RoB 2.0 and ROBINS-I) and all studies showed a negative effect of intervention. Sleep deprivation and intermittent hypoxia in children with OSAS seem to trigger a cascade of inflammatory pathways that exacerbate the tissue response to the release of reactive oxygen species and the generation of oxidative stress, leading to a reduction in oxygen supply to the intestinal mucosa and the integral destruction of the intestinal barrier. More evidence-based investigations are needed to optimize the identification of possible alterations in the gut microbiota of pediatric patients, given that its composition may be influenced by the patient's sleep quality and, consequently, by OSAS, showing quantitative and qualitative alterations compared to that found in healthy individuals.

Association Between Gut and Nasal Microbiota and Allergic Rhinitis: A Systematic Review

Allergic rhinitis is a chronic non-infectious inflammation of the nasal mucosa mediated by specific IgE. Recently, the human microbiome has drawn broad interest as a potential new target for treating this condition. This paper succinctly summarizes the main findings of 17 eligible studies published by February 2024, involving 1044 allergic rhinitis patients and 954 healthy controls from 5 countries. These studies examine differences in the human microbiome across important mucosal interfaces, including the nasal and intestinal areas, between patients and controls. Overall, findings suggest variations in the gut microbiota between allergic rhinitis patients and healthy individuals, although the specific bacterial taxa that significantly changed were not always consistent across studies. Due to the limited scope of existing research and patient coverage, the relationship between the nasal microbiome and allergic rhinitis remains inconclusive. The article discusses the potential immune-regulating role of the gut microbiome in allergic rhinitis. Further well-designed clinical trials with large-scale recruitment of allergic rhinitis patients are encouraged.

Harnessing human microbiomes for disease prediction

The human microbiome has been increasingly recognized as having potential use for disease prediction. Predicting the risk, progression, and severity of diseases holds promise to transform clinical practice, empower patient decisions, and reduce the burden of various common diseases, as has been demonstrated for cardiovascular disease or breast cancer. Combining multiple modifiable and non-modifiable risk factors, including high-dimensional genomic data, has been traditionally favored, but few studies have incorporated the human microbiome into models for predicting the prospective risk of disease. Here, we review research into the use of the human microbiome for disease prediction with a particular focus on prospective studies as well as the modulation and engineering of the microbiome as a therapeutic strategy.

Nasopharyngeal microbiota in children is associated with severe asthma exacerbations

BACKGROUND

The respiratory microbiome has been associated with the etiology and disease course of asthma.

OBJECTIVE

We sought to assess the nasopharyngeal microbiota in children with a severe asthma exacerbation and their associations with medication, air quality, and viral infection.

METHODS

A cross-sectional study was performed among children aged 2 to 18 years admitted to the medium care unit (MCU; n = 84) or intensive care unit (ICU; n = 78) with an asthma exacerbation. For case-control analyses, we matched all cases aged 2 to 6 years (n = 87) to controls in a 1:2 ratio. Controls were participants of either a prospective case-control study or a longitudinal birth cohort (n = 182). The nasopharyngeal microbiota was characterized by 16S-rRNA-gene sequencing.

RESULTS

Cases showed higher Shannon diversity index (ICU and MCU combined; P = .002) and a distinct microbial community composition when compared with controls (permutational multivariate ANOVA R2 = 1.9%; P < .001). We observed significantly higher abundance of Staphylococcus and "oral" taxa, including Neisseria, Veillonella, and Streptococcus spp. and a lower abundance of Dolosigranulum pigrum, Corynebacterium, and Moraxella spp. (MaAsLin2; q < 0.25) in cases versus controls. Furthermore, Neisseria abundance was associated with more severe disease (ICU vs MCU MaAslin2, P = .03; q = 0.30). Neisseria spp. abundance was also related with fine particulate matter exposure, whereas Haemophilus and Streptococcus abundances were related with recent inhaled corticosteroid use. We observed no correlations with viral infection.

CONCLUSIONS

Our results demonstrate that children admitted with asthma exacerbations harbor a microbiome characterized by overgrowth of Staphylococcus and "oral" microbes and an underrepresentation of beneficial niche-appropriate commensals. Several of these associations may be explained by (environmental or medical) exposures, although cause-consequence relationships remain unclear and require further investigations.

Airway epithelium respiratory illnesses and allergy (AERIAL) birth cohort: study protocol

Introduction

Recurrent wheezing disorders including asthma are complex and heterogeneous diseases that affect up to 30% of all children, contributing to a major burden on children, their families, and global healthcare systems. It is now recognized that a dysfunctional airway epithelium plays a central role in the pathogenesis of recurrent wheeze, although the underlying mechanisms are still not fully understood. This prospective birth cohort aims to bridge this knowledge gap by investigating the influence of intrinsic epithelial dysfunction on the risk for developing respiratory disorders and the modulation of this risk by maternal morbidities, in utero exposures, and respiratory exposures in the first year of life.

Methods

The Airway Epithelium Respiratory Illnesses and Allergy (AERIAL) study is nested within the ORIGINS Project and will monitor 400 infants from birth to 5 years. The primary outcome of the AERIAL study will be the identification of epithelial endotypes and exposure variables that influence the development of recurrent wheezing, asthma, and allergic sensitisation. Nasal respiratory epithelium at birth to 6 weeks, 1, 3, and 5 years will be analysed by bulk RNA-seq and DNA methylation sequencing. Maternal morbidities and in utero exposures will be identified on maternal history and their effects measured through transcriptomic and epigenetic analyses of the amnion and newborn epithelium. Exposures within the first year of life will be identified based on infant medical history as well as on background and symptomatic nasal sampling for viral PCR and microbiome analysis. Daily temperatures and symptoms recorded in a study-specific Smartphone App will be used to identify symptomatic respiratory illnesses.

Discussion

The AERIAL study will provide a comprehensive longitudinal assessment of factors influencing the association between epithelial dysfunction and respiratory morbidity in early life, and hopefully identify novel targets for diagnosis and early intervention.

The microbiome: an integral player in immune homeostasis and inflammation in the respiratory tract

The last decade of microbiome research has highlighted its fundamental role in systemic immune and metabolic homeostasis. The microbiome plays a prominent role during gestation and into early life, when maternal lifestyle factors shape immune development of the newborn. Breast milk further shapes gut colonization, supporting the development of tolerance to commensal bacteria and harmless antigens while preventing outgrowth of pathogens. Environmental microbial and lifestyle factors that disrupt this process can dysregulate immune homeostasis, predisposing infants to atopic disease and childhood asthma. In health, the low-biomass lung microbiome, together with inhaled environmental microbial constituents, establishes the immunological set point that is necessary to maintain pulmonary immune defense. However, in disease perturbations to immunological and physiological processes allow the upper respiratory tract to act as a reservoir of pathogenic bacteria, which can colonize the diseased lung and cause severe inflammation. Studying these host-microbe interactions in respiratory diseases holds great promise to stratify patients for suitable treatment regimens and biomarker discovery to predict disease progression. Preclinical studies show that commensal gut microbes are in a constant flux of cell division and death, releasing microbial constituents, metabolic by-products, and vesicles that shape the immune system and can protect against respiratory diseases. The next major advances may come from testing and utilizing these microbial factors for clinical benefit and exploiting the predictive power of the microbiome by employing multiomics analysis approaches.

Advances in co-pathogenesis of the united airway diseases

According to the concept of "united airway diseases", the airway is a single organ in which upper and lower airway diseases are commonly comorbid. A range of inflammatory factors have been found to play an important role in the chain reaction of upper and lower airway diseases. However, the amount of research on this concept remains limited. The underlying mechanism of the relationship between typical diseases of the united airway, such as asthma, allergic rhinitis, and chronic sinusitis, also needs to be further explored. This review highlights the interaction between upper and lower respiratory diseases gathered from epidemiological, histoembryology, neural mechanistic, microbiological, and clinical studies, revealing the relationship between the upper and lower respiratory tracts.

Can Therapeutic Targeting of the Human Microbiome Influence Asthma Management? A Pro/Con Debate

Asthma is a clinically heterogeneous disease, and despite substantial improvements in therapies, there remains an unmet need for well-tolerated, effective treatments. Observational studies have demonstrated that alterations in the respiratory and gut microbiome are associated with the development of asthma and its severity. These findings are supported by preclinical models demonstrating that respiratory and gut microbes can alter airway inflammation. Therapeutic approaches to target the human microbiome have been increasingly applied to a wide range of acute and chronic diseases, but there are currently no microbiome-based therapeutics approved for the treatment of asthma. This clinical commentary addresses the future role of microbiome-based therapeutics in asthma management from both a pro and con perspective. We examine (1) the prospects for clinical studies demonstrating a causal relationship between the human microbiome and the severity of asthma; (2) the challenges and potential solutions for designing, testing, and implementing a microbiome-based therapeutic; and (3) the possibility of microbiome-based therapeutics for conditions comorbid to asthma. We conclude by identifying research priorities that will help determine the future of microbiome-based therapeutics for the management of asthma.

Keratinocyte-derived small extracellular vesicles supply antigens for CD1a-resticted T cells and promote their type 2 bias in the context of filaggrin insufficiency

Introduction

Exosome-enriched small extracellular vesicles (sEVs) are nanosized organelles known to participate in long distance communication between cells, including in the skin. Atopic dermatitis (AD) is a chronic inflammatory skin disease for which filaggrin (FLG) gene mutations are the strongest genetic risk factor. Filaggrin insufficiency affects multiple cellular function, but it is unclear if sEV-mediated cellular communication originating from the affected keratinocytes is also altered, and if this influences peptide and lipid antigen presentation to T cells in the skin.

Methods

Available mRNA and protein expression datasets from filaggrin-insufficient keratinocytes (shFLG), organotypic models and AD skin were used for gene ontology analysis with FunRich tool. sEVs secreted by shFLG and control shC cells were isolated from conditioned media by differential centrifugation. Mass spectrometry was carried out for lipidomic and proteomic profiling of the cells and sEVs. T cell responses to protein, peptide, CD1a lipid antigens, as well as phospholipase A2-digested or intact sEVs were measured by ELISpot and ELISA.

Results

Data analysis revealed extensive remodeling of the sEV compartment in filaggrin insufficient keratinocytes, 3D models and the AD skin. Lipidomic profiles of shFLGsEV showed a reduction in the long chain (LCFAs) and polyunsaturated fatty acids (PUFAs; permissive CD1a ligands) and increased content of the bulky headgroup sphingolipids (non-permissive ligands). This resulted in a reduction of CD1a-mediated interferon-γ T cell responses to the lipids liberated from shFLG-generated sEVs in comparison to those induced by sEVs from control cells, and an increase in interleukin 13 secretion. The altered sEV lipidome reflected a generalized alteration in the cellular lipidome in filaggrin-insufficient cells and the skin of AD patients, resulting from a downregulation of key enzymes implicated in fatty acid elongation and desaturation, i.e., enzymes of the ACSL, ELOVL and FADS family.

Discussion

We determined that sEVs constitute a source of antigens suitable for CD1a-mediated presentation to T cells. Lipids enclosed within the sEVs secreted on the background of filaggrin insufficiency contribute to allergic inflammation by reducing type 1 responses and inducing a type 2 bias from CD1a-restricted T cells, thus likely perpetuating allergic inflammation in the skin.

Global knowledge mapping and emerging research trends in the microbiome and asthma: A bibliometric and visualized analysis using VOSviewer and CiteSpace

Background

Numerous prior studies have extensively highlighted the significance of the microbiome in association with asthma. While several studies have concentrated on the asthma microbiome in previous research, there is currently a lack of publications that employ bibliometric methods to assess this area.

Methods

In this study, the Web of Science Core Collection database was utilized as the data source, and the SCI-EXPANDED index was employed to ensure that the retrieved data were comprehensive and accurate. All original research articles and review articles related to the correlation between asthma and the microbiome were systematically searched from the inception of the database until June 20, 2023. These articles were subsequently visualized and analyzed using VOSviewer and CiteSpace software.

Results

A total of 1366 relevant publications were acquired, indicating a consistent annual increase in global publications in the field. The United States and China emerged as the top two contributors to international publications. Among prolific authors, Susan V. Lynch achieved the highest publication record, with Hans Bisgaard and Jakob Stokholm sharing the second position. The majority of publications concentrated on allergy-related and microbiome areas, with a few comprehensive journals standing out. Journals with 40 or more publications included the Journal of Allergy and Clinical Immunology, Allergy, Frontiers in Immunology, and PLOS One. The top 5 cited journals were the Journal of Allergy and Clinical Immunology, PLOS One, American Journal of Respiratory and Critical Care Medicine, Clinical and Experimental Allergy, and Nature. Upon analyzing keywords, high-frequency terms, such as asthma, gut microbiota, microbiome, children, childhood asthma, allergy, risk, exposure, inflammation, diversity, and chain fatty acids emerged as representative terms in the field.

Conclusion

This study systematically presented a comprehensive overview of the literature regarding the association between asthma and the microbiome over the last two decades. Through a bibliometric perspective, the findings may assist researchers with a better understanding of the essential information in the field.

What Makes the Gut-Lung Axis Working? From the Perspective of Microbiota and Traditional Chinese Medicine

Background

An increasing number of studies have proved that gut microbiota is involved in the occurrence and development of various lung diseases and can interact with the diseased lung. The concept of the gut-lung axis (GLA) provides a new idea for the subsequent clinical treatment of lung diseases through human microbiota. This review aims to summarize the microbiota in the lung and gut and the interaction between them from the perspectives of traditional Chinese medicine and modern medicine.

Method

We conducted a literature search by using the search terms "GLA," "gut microbiota," "spleen," and "Chinese medicine" in the databases PubMed, Web of Science, and CNKI. We then explored the mechanism of action of the gut-lung axis from traditional Chinese medicine and modern medicine.

Results

The lung and gut microbiota enable the GLA to function through immune regulation, while metabolites of the gut microbiota also play an important role. The spleen can improve the gut microbiota to achieve the regulation of the GLA.

Conclusion

Improving the gut microbiota through qi supplementation and spleen fortification provides a new approach to the clinical treatment of lung diseases by regulating the GLA. Currently, our understanding of the GLA is limited, and more research is needed to explain its working principle.

Positioning the preventive potential of microbiome treatments for cystic fibrosis in the context of current therapies

Antibiotics and cystic fibrosis transmembrane conductance regulator (CFTR) modulators play a pivotal role in cystic fibrosis (CF) treatment, but both have limitations. Antibiotics are linked to antibiotic resistance and disruption of the airway microbiome, while CFTR modulators are not widely accessible, and structural lung damage and pathogen overgrowth still occur. Complementary strategies that can beneficially modulate the airway microbiome in a preventive way are highly needed. This could be mediated via oral probiotics, which have shown some improvement of lung function and reduction of airway infections and exacerbations, as a cost-effective approach. However, recent data suggest that specific and locally administered probiotics in the respiratory tract might be a more targeted approach to prevent pathogen outgrowth in the lower airways. This review aims to summarize the current knowledge on the CF airway microbiome and possibilities of microbiome treatments to prevent bacterial and/or viral infections and position them in the context of current CF therapies.

Winds of change a tale of: asthma and microbiome

The role of the microbiome in asthma is highlighted, considering its influence on immune responses and its connection to alterations in asthmatic patients. In this context, we review the variables influencing asthma phenotypes from a microbiome perspective and provide insights into the microbiome's role in asthma pathogenesis. Previous cohort studies in patients with asthma have shown that the presence of genera such as Bifidobacterium, Lactobacillus, Faecalibacterium, and Bacteroides in the gut microbiome has been associated with protection against the disease. While, the presence of other genera such as Haemophilus, Streptococcus, Staphylococcus, and Moraxella in the respiratory microbiome has been implicated in asthma pathogenesis, indicating a potential link between microbial dysbiosis and the development of asthma. Furthermore, respiratory infections have been demonstrated to impact the composition of the upper respiratory tract microbiota, increasing susceptibility to bacterial diseases and potentially triggering asthma exacerbations. By understanding the interplay between the microbiome and asthma, valuable insights into disease mechanisms can be gained, potentially leading to the development of novel therapeutic approaches.

The respiratory microbiome in childhood asthma

Asthma is the most prevalent noncommunicable disease in childhood, characterized by reversible airway constriction and inflammation of the lower airways. The respiratory tract consists of the upper and lower airways, which are lined with a diverse community of microbes. The composition and density of the respiratory microbiome differs across the respiratory tract, with microbes adapting to the gradually changing physiology of the environment. Over the past decade, both the upper and lower respiratory microbiomes have been implicated in the etiology and disease course of asthma, as well as in its severity and phenotype. We have reviewed the literature on the role of the respiratory microbiome in asthma, making a careful distinction between the relationship of the microbiome with development of childhood asthma and its relationship with the disease course, while accounting for age and the microbial niches studied. Furthermore, we have assessed the literature regarding the underlying asthma endotypes and the impact of the microbiome on the host immune response. We have identified distinct microbial signatures across the respiratory tract associated with asthma development, stability, and severity. These data suggest that the respiratory microbiome may be important for asthma development and severity and may therefore be a potential target for future microbiome-based preventive and treatment strategies.

Salivary microbiome and asthma risk in children with orofacial defects

BACKGROUND

Patients with congenital orofacial defects, cleft lip (CL), cleft palate (CP), and cleft lip and palate (CLP) have continuous exposure of the respiratory system to the microbiome from the oral environment, offering opportunities to develop mucosal immunity in the airway. This two-part study aims to analyze data on asthma occurrence in CL, CP, and CLP infants and the composition of the salivary microbiome, and to evaluate the oral microbiota and its association with the risk of developing childhood asthma.

METHODS

Patient data from the research database of Chang Gung Memorial Hospital from 2004 to 2015 were retrospectively analyzed by multivariable regression. Diseases diagnoses were defined by ICD codes. Asthma must also meet the criteria for receiving selective β2 agonistic or/and inhaled corticosteroid treatments twice within 1 year. Analysis of the saliva microbiome was performed prospectively from 2016 to 2020 in 10 healthy term infants and 10 CLP infants on postnatal 7th day, 1 month, and 6 months by next-generation sequencing.

RESULTS

Asthma and nonasthma groups included 988 and 3952 patients, respectively. The incidence of asthma development was higher in patients with CP than in CL and CLP groups (aOR: 5.644, CI: 1.423-22.376). The species composition of the microbiome at 1 and 6 months was significantly different between infants with CLP and healthy infants.

CONCLUSION

Children with orofacial defects have a higher risk of developing asthma with a possible contribution from oral microbiota in the early months of life.

Severe Asthma and Biological Therapies: Now and the Future

Recognition of phenotypic variability in pediatric asthma allows for a more personalized therapeutic approach. Knowledge of the underlying pathophysiological and molecular mechanisms (endotypes) of corresponding biomarkers and new treatments enables this strategy to progress. Biologic therapies for children with severe asthma are becoming more relevant in this sense. The T2 phenotype is the most prevalent in childhood and adolescence, and non-T2 phenotypes are usually rare. This document aims to review the mechanism of action, efficacy, and potential predictive and monitoring biomarkers of biological drugs, focusing on the pediatric population. The drugs currently available are omalizumab, mepolizumab, benralizumab, dupilumab, and 1ezepelumab, with some differences in administrative approval prescription criteria between the U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMA). Previously, we described the characteristics of severe asthma in children and its diagnostic and therapeutic management.

Limosilactobacillus reuteri in immunomodulation: molecular mechanisms and potential applications

Frequent use of hormones and drugs may be associated with side-effects. Recent studies have shown that probiotics have effects on the prevention and treatment of immune-related diseases. Limosilactobacillus reuteri (L. reuteri) had regulatory effects on intestinal microbiota, host epithelial cells, immune cells, cytokines, antibodies (Ab), toll-like receptors (TLRs), tryptophan (Try) metabolism, antioxidant enzymes, and expression of related genes, and exhibits antibacterial and anti-inflammatory effects, leading to alleviation of disease symptoms. Although the specific composition of the cell-free supernatant (CFS) of L. reuteri has not been clarified, its efficacy in animal models has drawn increased attention to its potential use. This review summarizes the effects of L. reuteri on intestinal flora and immune regulation, and discusses the feasibility of its application in atopic dermatitis (AD), asthma, necrotizing enterocolitis (NEC), systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and multiple sclerosis (MS), and provides insights for the prevention and treatment of immune-related diseases.

The Fungal Microbiome of the Upper Airway Is Associated With Future Loss of Asthma Control and Exacerbation Among Children With Asthma

BACKGROUND

Accumulating evidence suggests that the upper airway bacterial microbiota is implicated in asthma inception, severity, and exacerbation. Unlike bacterial microbiota, the role of the upper airway fungal microbiome (mycobiome) in asthma control is poorly understood.

RESEARCH QUESTION

What are the upper airway fungal colonization patterns among children with asthma and their relationship with subsequent loss of asthma control and exacerbation of asthma?

STUDY DESIGN AND METHODS

The study was coupled with the Step Up Yellow Zone Inhaled Corticosteroids to Prevent Exacerbations (ClinicalTrials.gov Identifier: NCT02066129) clinical trial. The upper airway mycobiome was investigated using Internal transcribed spacer 1 (ITS1) sequencing of nasal blow samples collected from children with asthma when asthma was well controlled (baseline, n = 194) and during early signs of loss of asthma control (yellow zone [YZ], n = 107).

RESULTS

At baseline, 499 fungal genera were detected in the upper airway samples, with two commensal fungal species, Malassezia globosa and Malassezia restricta, being most dominant. The relative abundance of Malassezia species varies by age, BMI, and race. Higher relative abundance of M globosa at baseline was associated with lower risk of future YZ episodes (P = .038) and longer time to development of first YZ episode (P = .022). Higher relative abundance of M globosa at YZ episode was associated with lower risk of progression from YZ episode to severe asthma exacerbation (P = .04). The upper airway mycobiome underwent significant changes from baseline to YZ episode, and increased fungal diversity was correlated highly with increased bacterial diversity (ρ = 0.41).

INTERPRETATION

The upper airway commensal mycobiome is associated with future asthma control. This work highlights the importance of the mycobiota in asthma control and may contribute to the development of fungi-based markers to predict asthma exacerbation.

Characterization of the upper respiratory tract microbiota in Chilean asthmatic children reveals compositional, functional, and structural differences

Around 155 million people worldwide suffer from asthma. In Chile, the prevalence of this disease in children is around 15% and has a high impact in the health system. Studies suggest that asthma is caused by multiple factors, including host genetics, antibiotic use, and the development of the airway microbiota. Here, we used 16S rRNA high-throughput sequencing to characterize the nasal and oral mucosae of 63 asthmatic and 89 healthy children (152 samples) from Santiago, Chile. We found that the nasal mucosa was dominated by a high abundance of Moraxella, Dolosigranulum, Haemophilus, Corynebacterium, Streptococcus, and Staphylococcus. In turn, the oral mucosa was characterized by a high abundance of Streptococcus, Haemophilus, Gemella, Veillonella, Neisseria, and Porphyromonas. Our results showed significantly (P < 0.001) lower alpha diversity and an over-abundance of Streptococcus (P < 0.01) in nasal samples from asthmatics compared to samples from healthy subjects. Community structure, as revealed by co-occurrence networks, showed different microbial interactions in asthmatic and healthy subjects, particularly in the nasal microbiota. The networks revealed keystone genera in each body site, including Prevotella, Leptotrichia, and Porphyromonas in the nasal microbiota, and Streptococcus, Granulicatella, and Veillonella in the oral microbiota. We also detected 51 functional pathways differentially abundant on the nasal mucosa of asthmatic subjects, although only 13 pathways were overrepresented in the asthmatic subjects (P < 0.05). We did not find any significant differences in microbial taxonomic (composition and structure) and functional diversity between the oral mucosa of asthmatic and healthy subjects. This study explores for the first time the relationships between the upper respiratory airways bacteriome and asthma in Chile. It demonstrates that the nasal cavity of children from Santiago harbors unique bacterial communities and identifies potential taxonomic and functional biomarkers of pediatric asthma.

Impact of local human microbiota on the allergic diseases: Organ-organ interaction

The homogeneous impact of local dysbiosis on the development of allergic diseases in the same organ has been thoroughly studied. However, much less is known about the heterogeneous influence of dysbiosis within one organ on allergic diseases in other organs. A comprehensive analysis of the current scientific literature revealed that most of the relevant publications focus on only three organs: gut, airways, and skin. Moreover, the interactions appear to be mainly unidirectional, that is, dysbiotic conditions of the gut being associated with allergic diseases of the airways and the skin. Similar to homogeneous interactions, early life appears to be not only a crucial period for the formation of the microbiota in one organ but also for the later development of allergic diseases in other organs. In particular, we were able to identify a number of specific bacterial and fungal species/genera in the intestine that were repeatedly associated in the literature with either increased or decreased allergic diseases of the skin, like atopic dermatitis, or the airways, like allergic rhinitis and asthma. The reported studies indicate that in addition to the composition of the microbiome, also the relative abundance of certain microbial species and the overall diversity are associated with allergic diseases of the corresponding organs. As anticipated for human association studies, the underlying mechanisms of the organ-organ crosstalk could not be clearly resolved yet. Thus, further work, in particular experimental animal studies are required to elucidate the mechanisms linking dysbiotic conditions of one organ to allergic diseases in other organs.

Respiratory eukaryotic virome expansion and bacteriophage deficiency characterize childhood asthma

Asthma development and exacerbation is linked to respiratory virus infections. There is limited information regarding the presence of viruses during non-exacerbation/infection periods. We investigated the nasopharyngeal/nasal virome during a period of asymptomatic state, in a subset of 21 healthy and 35 asthmatic preschool children from the Predicta cohort. Using metagenomics, we described the virome ecology and the cross-species interactions within the microbiome. The virome was dominated by eukaryotic viruses, while prokaryotic viruses (bacteriophages) were independently observed with low abundance. Rhinovirus B species consistently dominated the virome in asthma. Anelloviridae were the most abundant and rich family in both health and asthma. However, their richness and alpha diversity were increased in asthma, along with the co-occurrence of different Anellovirus genera. Bacteriophages were richer and more diverse in healthy individuals. Unsupervised clustering identified three virome profiles that were correlated to asthma severity and control and were independent of treatment, suggesting a link between the respiratory virome and asthma. Finally, we observed different cross-species ecological associations in the healthy versus the asthmatic virus-bacterial interactome, and an expanded interactome of eukaryotic viruses in asthma. Upper respiratory virome "dysbiosis" appears to be a novel feature of pre-school asthma during asymptomatic/non-infectious states and merits further investigation.

Alterations of nasal microbiome in eosinophilic chronic rhinosinusitis

BACKGROUND

Exposure to microbes may be important in the development of chronic rhinosinusitis (CRS). Dysbiosis of the nasal microbiome is considered to be related to CRS with nasal polyps (CRSwNP). The link between the nasal microbiota and eosinophilic CRSwNP (eCRSwNP) has rarely been studied.

OBJECTIVE

The aim of this study was to rigorously characterize nasal dysbiosis in a cohort of patients with eCRSwNP and compare the nasal microbiomes of these patients with those of healthy controls (HCs).

METHODS

We performed a cross-sectional study of 34 patients with eCRSwNP, 10 patients without CRSwNP, and 44 HCs by using 16S rRNA gene sequencing. An independent cohort of 14 patients with eCRSwNP, 9 patients without CRSwNP, and 11 HCs was used to validate the results.

RESULTS

Compared with the nasal microbiome of healthy controls, the nasal microbiome of patients with eCRSwNP was characterized by higher α-diversity (Shannon and Chao1 index) and a distinct composition of microbes. Notably, the distinct differences in microbial composition between patients with eCRSwNP and HCs were significantly correlated with eCRSwNP disease status. Furthermore, in a diagnostic model generated by using these differences, a combination of 15 genera could be used to distinguish patients with eCRSwNP from HCs, with an area under the curve of approximately 0.8 in both the exploration and validation cohorts.

CONCLUSION

Our study establishes the compositional alterations in the nasal microbiome in eCRSwNP and suggests the potential for using the nasal microbiota as a noninvasive predictive classifier for the diagnosis of eCRSwNP.

Bacterial Microbiota of Asthmatic Children and Preschool Wheezers' Airways-What Do We Know?

Asthma is the most chronic pulmonary disease in pediatric population, and its etiopathology still remains unclear. Both viruses and bacteria are suspected factors of disease development and are responsible for its exacerbation. Since the launch of The Human Microbiome Project, there has been an explosion of research on microbiota and its connection with various diseases. In our review, we have collected recent data about both upper- and lower-airway bacterial microbiota of asthmatic children. We have also included studies regarding preschool wheezers, since asthma diagnosis in children under 5 years of age remains challenging due to the lack of an objective tool. This paper indicates the need for further studies of microbiome and asthma, as in today's knowledge, there is no particular bacterium that discriminates the asthmatics from the healthy peers and can be used as a potential biological factor in the disease prevalence and treatment.

The Impact of Smoking on Microbiota: A Narrative Review

Cigarette smoke is a classic risk factor for many diseases. The microbiota has been recently indicated as a new, major player in human health. Its deregulation-dysbiosis-is considered a new risk factor for several illnesses. Some studies highlight a cross-interaction between these two risk factors-smoke and dysbiosis-that may explain the pathogenesis of some diseases. We searched the keywords "smoking OR smoke AND microbiota" in the title of articles on PubMed®, UptoDate®, and Cochrane®. We included articles published in English over the last 25 years. We collected approximately 70 articles, grouped into four topics: oral cavity, airways, gut, and other organs. Smoke may impair microbiota homeostasis through the same harmful mechanisms exerted on the host cells. Surprisingly, dysbiosis and its consequences affect not only those organs that are in direct contact with the smoke, such as the oral cavity or the airways, but also involve distant organs, such as the gut, heart, vessels, and genitourinary tract. These observations yield a deeper insight into the mechanisms implicated in the pathogenesis of smoke-related diseases, suggesting a role of dysbiosis. We speculate that modulation of the microbiota may help prevent and treat some of these illnesses.

Interactions between microbiome and underlying mechanisms in asthma

Microbiome primes host innate immunity in utero and play fundamental roles in the development, training, and function of the immune system throughout the life. Interplay between the microbiome and immune system maintains mucosal homeostasis, while alterations of microbial community dysregulate immune responses, leading to distinct phenotypic features of immune-mediated diseases including asthma. Microbial imbalance within the mucosal environments, including upper and lower airways, skin, and gut, has consistently been observed in asthma patients and linked to increased asthma exacerbations and severity. Microbiome research has increased to uncover hidden microbial members, function, and immunoregulatory effects of bacterial metabolites within the mucosa. This review provides an overview of environmental and genetic factors that modulate the composition and function of the microbiome, and the impacts of microbiome metabolites and skin microbiota on immune regulation in asthma.

KGNMDA: A Knowledge Graph Neural Network Method for Predicting Microbe-Disease Associations

Accumulated studies discovered that various microbes in human bodies were closely related to complex human diseases and could provide new insight into drug development. Multiple computational methods were constructed to predict microbes that were potentially associated with diseases. However, most previous methods were based on single characteristics of microbes or diseases, that lacked important biological information related to microorganisms or diseases. Therefore, we constructed a knowledge graph centered on microorganisms and diseases from several existed databases to provide knowledgeable information for microbes and diseases. Then, we adopted a graph neural network method to learn representations of microbes and diseases from the constructed knowledge graph. After that, we introduced the Gaussian kernel similarity features of microbes and diseases to generate final representations of microbes and diseases. At last, we proposed a score function on final representations of microbes and diseases to predict scores of microbe-disease associations. Comprehensive experiments on the Human Microbe-Disease Association Database (HMDAD) dataset had demonstrated that our approach outperformed baseline methods. Furthermore, we implemented case studies on two important diseases (asthma and inflammatory bowel disease), the result demonstrated that our proposed model was effective in revealing the relationship between diseases and microbes. The source code of our model and the data were available on https://github.com/ChangzhiJiang/KGNMDA_master.

The upper-airway microbiome as a biomarker of asthma exacerbations despite inhaled corticosteroid treatment

BACKGROUND

The response to inhaled corticosteroids (ICS) in asthma is affected by the interplay of several factors. Among these, the role of the upper-airway microbiome has been scarcely investigated. We aimed to evaluate the association between the salivary, pharyngeal, and nasal microbiome with asthma exacerbations despite receipt of ICS.

METHODS

Samples from 250 asthma patients from the Genomics and Metagenomics of Asthma Severity (GEMAS) study treated with ICS were analyzed. Control/case subjects were defined by the absence/presence of asthma exacerbations in the past 6 months despite being treated with ICS. The bacterial microbiota was profiled by sequencing the V3-V4 region of the 16S rRNA gene. Differences between groups were assessed by PERMANOVA and regression models adjusted for potential confounders. A false discovery rate (FDR) of 5% was used to correct for multiple comparisons. Classification models of asthma exacerbations despite ICS treatment were built with machine learning approaches based on clinical, genetic, and microbiome data.

RESULTS

In nasal and saliva samples, case subjects had lower bacterial diversity (Richness, Shannon, and Faith indices) than control subjects (.007 ≤ P ≤ .037). Asthma exacerbations accounted for 8% to 9% of the interindividual variation of the salivary and nasal microbiomes (.003 ≤ P ≤ .046). Three, 4, and 11 bacterial genera from the salivary, pharyngeal, and nasal microbiomes were differentially abundant between groups (4.09 × 10^-12 ≤ FDR ≤ 0.047). Integrating clinical, genetic, and microbiome data showed good discrimination for the development of asthma exacerbations despite receipt of ICS (AUC_training: 0.82 and AUC_validation: 0.77).

CONCLUSION

The diversity and composition of the upper-airway microbiome are associated with asthma exacerbations despite ICS treatment. The salivary microbiome has a potential application as a biomarker of asthma exacerbations despite receipt of ICS.

The Human Respiratory Microbiome: Current Understandings and Future Directions

Microorganisms colonize the human body. The lungs and respiratory tract, previously believed to be sterile, harbor diverse microbial communities and the genomes of bacteria (bacteriome), viruses (virome), and fungi (mycobiome). Recent advances in amplicon and shotgun metagenomic sequencing technologies and data-analyzing methods have greatly aided the identification and characterization of microbial populations from airways. The respiratory microbiome has been shown to play roles in human health and disease and is an area of rapidly emerging interest in pulmonary medicine. In this review, we provide updated information in the field by focusing on four lung conditions, including asthma, chronic obstructive pulmonary disease, cystic fibrosis, and idiopathic pulmonary fibrosis. We evaluate gut, oral, and upper airway microbiomes and how they contribute to lower airway flora. The discussion is followed by a systematic review of the lower airway microbiome in health and disease. We conclude with promising research avenues and implications for evolving therapeutics.

Residential greenness and air pollution's association with nasal microbiota among asthmatic children

Both greenness and air pollution have widely been linked with asthma. However, the potential mechanism has rarely been investigated. This study aimed to identify the association between residential greenness and air pollution (fine particulate matter [PM_2.5]; nitrogen dioxide [NO₂]; ozone [O₃]) with nasal microbiota among asthmatic children during the recovery phase. The normalized difference vegetation index was used to assess the extent of residential greenness. Spatiotemporal air pollution variation was estimated using an integrated hybrid kriging-LUR with the XG-Boost algorithm. These exposures were measured in 250-m intervals for four incremental buffer ranges. Nasal microbiota was collected from 47 children during the recovery phase. A generalized additive model controlled for various covariates was applied to evaluate the exposure-outcome association. The lag-time effect of greenness and air pollution related to the nasal microbiota also was examined. A significant negative association was observed between short-term exposure to air pollution and nasal bacterial diversity, as a one-unit increment in PM_2.5 or O₃ significantly decreased the observed species (PM_2.5: -0.59, 95%CI -1.13, -0.05 and O₃: -0.93, 95%CI -1.54, -0.32) and species richness (PM_2.5: -0.64, 95%CI -1.25, -0.02 and O₃: -0.68, 95%CI -1.43, -0.07). Considering the lag-time effect, we found a significant positive association between greenness and both the observed species and species richness. In addition, we identified a significant negative association for all pollutants with the observed species richness. These findings add to the evidence base of the links between nasal microbiota and air pollution and greenness. This study establishes a foundation for future studies of how environmental exposure plays a role in nasal microbiota, which in turn may affect the development of asthma.

Understanding the Functional Role of the Microbiome and Metabolome in Asthma

PURPOSE OF REVIEW

Asthma is a heterogenous respiratory disease characterized by airway inflammation and obstruction. However, the causes of asthma are unknown. Several studies have reported microbial and metabolomic dysbiosis in asthmatic patients; but, little is known about the functional role of the microbiota or the host-microbe metabolome in asthma pathophysiology. Current multi-omic studies are linking both the metabolome and microbiome in different organ systems to help identify the interactions involved in asthma, with the goal of better identifying endotypes/phenotypes, causal links, and potential targets of treatment. This review thus endeavors to explore the benefits of and current advances in studying microbiome-metabolome interactions in asthma.

RECENT FINDINGS

This is a narrative review of the current state of research surrounding the interaction between the microbiome and metabolome and their role in asthma. Associations with asthma onset, severity, and phenotype have been identified in both the microbiome and the metabolome, most frequently in the gut. More recently, studies have begun to investigate the role of the respiratory microbiome in airway disease and its association with the systemic metabolome, which has provided further insights into its role in asthma phenotypes. This review also identifies gaps in the field in understanding the direct link between respiratory microbiome and metabolome, hypothesizes the benefits for conducting such studies in the future for asthma treatment and prevention, and identifies current analytical limitations that need to be addressed to advance the field. This is a comprehensive review of the current state of research on the interaction between the microbiome and metabolome and their role in asthma.