THE ASTHMA microbiome is increasingly recognised as a key factor in asthma, a chronic respiratory condition marked by wheeze, breathlessness, and airway inflammation. However, most evidence guiding asthma treatment comes from high-income countries. A new international study suggests that while airway bacteria and inflammation vary widely across regions, some microbiome–inflammation links in asthma are surprisingly consistent worldwide.
Asthma Microbiome Differs Across Countries
Researchers analysed induced sputum samples from nearly 500 young people with and without asthma across five countries: Brazil, Ecuador, Uganda, New Zealand and the UK. The study examined inflammatory cell patterns alongside detailed microbiota profiles, including overall bacterial load and specific respiratory pathogens.
Marked geographic differences emerged. Participants from Uganda showed higher levels of neutrophilic inflammation, greater bacterial abundance, and increased microbial diversity compared with other regions. In contrast, asthma in high-income settings more often reflected inflammatory patterns typically described in existing guidelines, highlighting how asthma characteristics differ globally.
Conserved Asthma Microbiome Signals In Neutrophilic Disease
Despite regional variation, the study identified conserved relationships between airway inflammation and the asthma microbiome. Across all centres, higher proportions of neutrophils were strongly associated with changes in overall microbiota composition.
Neutrophilic inflammation consistently correlated with increased bacterial burden, including higher loads of Haemophilus influenzae and Moraxella catarrhalis, often linked to more severe or treatment-resistant asthma. These associations were seen regardless of geography, suggesting a shared biological pattern within neutrophilic asthma.
Eosinophils Show Weaker Microbiome Links
Eosinophilic inflammation, another common asthma phenotype often targeted by current therapies, showed weaker and more limited associations with the asthma microbiome. Higher eosinophil proportions were linked mainly to increased Streptococcus abundance and explained less overall variation in microbial composition.
For clinicians, this distinction is important. It reinforces the idea that neutrophilic asthma may represent a microbiologically distinct endotype, potentially less responsive to standard anti-inflammatory treatments.
Implications For Global Asthma Care
The findings highlight a mismatch between current asthma treatment models and the disease patterns seen in many low- and middle-income settings. While local environmental and microbial exposures shape asthma expression, conserved asthma microbiome–neutrophil relationships point to shared mechanisms that could inform future therapies.
Although the cross-sectional design limits causal conclusions, the study strengthens the case for integrating microbiome-informed approaches into asthma research and care, particularly for patients with neutrophilic disease who remain poorly served by existing treatment strategies.
Reference
Taylor SL et al; WASP Study Group. Airway microbiota in young people across four continents differ by country, asthma status and inflammatory phenotype. Thorax. 2026; doi:10.1136/thorax-2025-222965.
