Upper-airway microbes predict asthma exacerbations despite inhaler treatment

Asthma exacerbations after treatment with inhaled corticosteroids (ICS) might be affected by upper-airway microbiome composition and diversity, a new study has found.

The study included 250 asthma patients who had undergone ICS treatment. Cases were defined as those who developed asthma exacerbations, while those who did not were designated as controls. 16S rRNA sequencing was used to assess the upper-airway microbiome and differences between cases and controls were detected using regression analysis and PERMANOVA.

Eighty-eight patients were ultimately classified as cases, while the rest were designated as controls. The former subgroup was much younger than the latter (median, 33.0 vs 46.5 years) and had higher use levels of antibiotics in the past 2 months.

Bacterial richness and diversity, as measured by the Shannon and Faith indices, were significantly lower in both salivary and nasal samples from cases vs controls. A similar trend was reported for pharyngeal microbiome but fell short of statistical significance.

In particular, three bacterial genera in salivary samples were significantly different between cases and controls. Correspondingly, four and eleven genera in pharyngeal and nasal samples could differentiate cases and controls.

Notably, exacerbations accounted for 8.6 percent and 9.1 percent of the inter-individual variation in the salivary and nasal microbiome, respectively.

“This is the first study assessing the salivary, nasal, and pharyngeal microbiome as potential predictive biomarkers of asthma exacerbations despite inhaled corticosteroid treatment,” the researchers said. “Saliva is a noninvasive and easily-collected sample that may improve current clinical models to predict asthma exacerbations despite inhaled corticosteroids use.”