Explore impact of inhaled glucocorticoids/β₂-agonists on the oropharyngeal microbiota in asthma patients impact of GCs/β₂-agonists on oropharyngeal microbiota in asthma

Asthma is a common chronic respiratory disease. Inhaled glucocorticoids (ICS) are first-line medications for asthma treatment. Studies suggest ICS use is associated with an increased risk of respiratory infections. Concurrently, multiple studies confirm a close association between respiratory microbiota and asthma, indicating that abnormal airway microbiota may be involved in the pathogenesis, progression, exacerbation, severity, disease control, and phenotypic characteristics of asthma. Whether treatment with inhaled glucocorticoids combined with long-acting β₂-agonists (ICS/LABA) affects the oropharyngeal microbiota in asthma patients, and whether this further influences treatment efficacy and prognosis, remains unclear. Using 16S rRNA amplicon sequencing and ITS gene sequencing technologies, we analyzed the bacterial and fungal microbiota in the oropharynx of 21 asthma patients who were in a clinically stable phase before and after 28 days of ICS/LABA treatment, comparing the composition and diversity of the microbial communities. Patients rinsed their mouths with water. A sterile swab was rotated twice against the posterior pharyngeal wall. ICS/LABA was taken on a fixed schedule. Significant differences were observed in the α-diversity of the oropharyngeal bacterial microbiota before and after ICS/LABA treatment in asthma patients. Post-treatment, bacterial richness and evenness significantly decreased. The relative abundances of the phylum Candidatus Saccharibacteria, genus Saccharibacteria, and species Streptococcus oralis were significantly lower in the post-treatment group compared to the pretreatment group. No significant differences were found in the α- or β-diversity of the oropharyngeal fungal microbiota pre- and post-treatment. However, the relative abundances of the genus Saccharomyces and species Saccharomyces cerevisiae were significantly lower post-treatment, while the relative abundances of the genus Fusarium and species Thermomyces lanuginosus were significantly higher. Association analysis revealed a decrease in Streptococcus abundance in the oropharynx of asthma patients after ICS/LABA treatment, suggesting a potential trend towards normalization of the bacterial microbiota, making it more similar to that of healthy individuals. The implications of the observed changes in oropharyngeal fungal microbiota following ICS/LABA treatment on asthma remain unclear and warrant further investigation.