The nasal microbiome: opening new clinical research avenues for allergic disease

Nasal Bacteriomes of Patients with Asthma and Allergic Rhinitis Show Unique Composition, Structure, Function and Interactions

Allergic rhinitis and asthma are major public health concerns and economic burdens worldwide. However, little is known about nasal bacteriome dysbiosis during allergic rhinitis, alone or associated with asthma comorbidity. To address this knowledge gap we applied 16S rRNA high-throughput sequencing to 347 nasal samples from participants with asthma (AS = 12), allergic rhinitis (AR = 53), allergic rhinitis with asthma (ARAS = 183) and healthy controls (CT = 99). One to three of the most abundant phyla, and five to seven of the dominant genera differed significantly (p < 0.021) between AS, AR or ARAS and CT groups. All alpha-diversity indices of microbial richness and evenness changed significantly (p < 0.01) between AR or ARAS and CT, while all beta-diversity indices of microbial structure differed significantly (p < 0.011) between each of the respiratory disease groups and controls. Bacteriomes of rhinitic and healthy participants showed 72 differentially expressed (p < 0.05) metabolic pathways each related mainly to degradation and biosynthesis processes. A network analysis of the AR and ARAS bacteriomes depicted more complex webs of interactions among their members than among those of healthy controls. This study demonstrates that the nose harbors distinct bacteriotas during health and respiratory disease and identifies potential taxonomic and functional biomarkers for diagnostics and therapeutics in asthma and rhinitis.

Microbiome in Nasal Mucosa of Children and Adolescents with Allergic Rhinitis: A Systematic Review

The human upper respiratory tract comprises the nasal cavity, pharynx and larynx regions and offers distinct microbial communities. However, an imbalance and alterations in the nasal mucosa microbiome enhance the risk of chronic respiratory conditions in patients with allergic respiratory diseases. This is particularly important in children and adolescents once allergic rhinitis (AR) is an inflammatory disorder of the nasal mucosa, often associated with an increase in pulmonary allergic inflammation. Therefore, this systematic review aimed to collect scientific data published concerning the microbial community alterations in nasal mucosa of children and adolescents suffering from AR or in association with adenotonsillar hypertrophy (AH) and allergic rhinoconjunctivitis (ARC). The current study was performed using the guidelines of Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Publications related to microbiome alterations in the nasal mucosa in pediatric age, studies including next-generation sequencing platforms, and studies exclusively written in the English language were some of the inclusion criteria. In total, five articles were included. Despite the scarcity of the published data in this research field and the lack of prospective studies, the genera Acinetobacter, Corynebacterium, Dolosigranulum, Haemophilus, Moraxella, Staphylococcus and Streptococcus dominate the nares and nasopharyngeal microbiome of the pediatric population regardless of their age. However, an imbalance in the resident bacterial community in the nasal mucosa was observed. The genera Acinetobacter, and Pseudomonas were more abundant in the nasal cavity of AR and AH children, while Streptococcus and Moraxella were predominant in the hypopharyngeal region of AR infants. An abundance of Staphylococcus spp. was also reported in the anterior nares and hypopharyngeal region of children and adolescents suffering from AR passive smoke exposure and ARC. These records suggest that different nasal structures, ageing, smoke exposure and the presence of other chronic disorders shape the nasal mucosa microbiome. Therefore, the establishment of adequate criteria for sampling would be established for a deeper understanding and a trustworthy comparison of the microbiome alterations in pediatric age.

Nasal Bacterial Microbiome Differs Between Healthy Controls and Those With Asthma and Allergic Rhinitis

Perturbation of the microbiome has numerous associations with the phenotypes and progression in chronic airways disease. However, the differences in the nasal microbiome in asthma and allergic rhinitis (AR) have not been defined. We examined whether the nasal microbiome would vary among different comorbidities in asthma and AR and that those differences may be associated with the severity of asthma. Nasal lavage fluid was collected from 110 participants, including 20 healthy controls, 30 subjects with AR, 30 subjects with asthma and 30 subjects with combined asthma + AR. The Asthma Control Questionnaire (ACQ-7) was used to evaluate asthma control status. Using 16S rRNA bacterial gene sequencing, we analyzed nasal microbiome in patients with asthma, AR, combined asthma + AR, and healthy controls. Bacterial diversity was analyzed in corresponding with α diversity indices (Chao and Shannon index). Compared with healthy controls, the Chao index tended to be lower in subjects with AR (P = 0.001), asthma (P = 0.001), and combined asthma + AR (P = 0.001) when compared with healthy controls. Furthermore, the Shannon index was significantly lower in subjects with asthma (P = 0.013) and comorbid asthma with AR (P = 0.004) than the control subjects. Disparity in the structure and composition of nasal bacteria were also observed among the four groups. Furthermore, patients with combined asthma + AR and isolated asthma were divided into two groups according to the level of disease control: partially or well-controlled and uncontrolled asthma. The mean relative abundance observed in the groups mentioned the genera of Pseudoflavonifractor were dominated in patients with well and partially controlled disease, in both isolated asthma and combined asthma + AR. In subjects with uncontrolled asthma and combined asthma + AR, a lower evenness and richness (Shannon index, P = 0.040) was observed in nasal microbiome composition. Importantly, lower evenness and richness in the nasal microbiome may be associated with poor disease control in combined asthma + AR. This study showed the upper airway microbiome is associated with airway inflammation disorders and the level of asthma control.

Efficacy of Pidotimod use in treating allergic rhinitis in a pediatric population

Background

Allergic rhinitis (AR) and adenoidal hypertrophy (AH) are the most frequent causative disorders of nasal obstruction in children, leading to recurrent respiratory infections. Both nasal cavities are colonized by a stable microbial community susceptible to environmental changes and Staphylococcus aureus seems to play the major role. Furthermore, nasal microbiota holds a large number and variety of viruses with upper respiratory tract infections. This local microbiota deserves attention because its modification could induce a virtuous cross-talking with the immune system, with a better clearance of pathogens. Although AR and AH present a different etiopathogenesis, they have in common a minimal chronic inflammation surrounding nasal obstruction; hence it would be challenging to evaluate the effect of an immunomodulator on this minimal chronic inflammation with possible clinical and microbiological effects. The aim of this study is therefore to evaluate the efficacy of an immunomoldulator (Pidotimod) on nasal obstruction in children with AR and/or AH and whether its action involves a variation of nasal microbiota.

Methods

We enrolled 76 children: those with allergic rhinitis (AR) sensitized to dust mites entered the AR group, those with adenoidal hypertrophy (AH) the AH group, those with both conditions the AR/AH group and those without AR ± AH as controls (CTRL). At the first visit they performed: skin prick tests, nasal fiberoptic endoscopy, anterior rhinomanometry, nasal swabs. Children with.

AR ± AH started treatment with Pidotimod.

After 1 month they were re-evaluated performing the same procedures.

The primary outcome was the evaluation of nasal obstruction after treatment and the secondary outcome was the improvement of symptoms and the changes in nasal microflora.

Results

All patients improved their mean nasal flow (mNF) in respect to the baseline. In AR children mNF reached that one of CTRL. In AH children±AR the mNF was lower in respect to CTRL and AR group. We did not find any differences among all the groups at the two different time points in nasal microflora.

Conclusions

Pidotimod is able to give an improvement in nasal obstruction, especially in AR children but this effect seems to be not mediated by changes in nasal microbiota.