Bacteria of the lung microbiome and health biomarkers in chronic airway disease: a systematic review and meta-analysis.

The lung microbiome is increasingly recognized as a key contributor to the development and progression of chronic airway diseases. While these conditions are typically associated with reduced microbial diversity and pathogen overgrowth, emerging evidence suggests that non-pathogenic bacteria may influence clinical outcomes. However, inconsistent findings across studies have made it difficult to determine their exact role in disease pathophysiology. To identify potentially beneficial members of the lung microbiome, we conducted a systematic review and meta-analysis of clinical studies investigating the association between non-pathogenic bacterial genera or species and clinico-pathological features in individuals with asthma, bronchiectasis, chronic obstructive pulmonary disease and cystic fibrosis. For the meta-analysis, data from different diseases were combined. Our analysis revealed that several bacteria in the lung microbiome were significantly associated with improved lung function and/or reduced airway inflammation across diseases. Although causal relationships cannot be established due to the absence of interventional studies, our findings highlight promising candidates for functional characterization and therapeutic exploration. Considerable heterogeneity in study design and reporting underscores the need for standardized methods and validation in relevant experimental models to advance our understanding of the lung microbiome in chronic airway diseases and inform the development of effective microbiome-based interventions.