Metagenomic next-generation sequencing reveals microbial community characteristics during acute exacerbations of interstitial pneumonia and their associations with clinical phenotypes.

OBJECTIVE

Accurate pathogen detection is crucial for clinical management of interstitial lung diseases (ILDs), but conventional culture methods (CMT) have limited sensitivity. This study evaluated the diagnostic performance of metagenomic next-generation sequencing (mNGS) versus CMT in ILD patients and characterized differences in lower respiratory microbiome between stable (Stable) and acute exacerbation (AE) stage, as well as their associations with clinical indicators.

METHODS

We retrospectively analyzed ILD patients admitted between September 2021 and November 2023. Multidisciplinary discussion (MDT)-based comprehensive diagnosis served as the reference standard. We compared the sensitivity, specificity, and accuracy of mNGS and CMT. Microbiome analyses were performed to assess community composition and diversity in the Stable and AE groups, and to explore correlations with clinical features (e.g., frequency of exacerbations, oxygenation index, inflammatory markers).

RESULTS

The sensitivity of mNGS (95.60%) was significantly higher than that of CMT (32.20%). In 61.80% of patients, only mNGS yielded positive results, highlighting its diagnostic advantage. A total of 77 microorganisms were detected; bacteria accounted for 66.67% (e.g., Streptococcus pneumoniae, Haemophilus parainfluenzae). Among fungi, Candida albicans and Pneumocystis jirovecii predominated. Microbial diversity was significantly lower in the AE group than in the Stable group (p < 0.01). Candida albicans (p = 0.032) and Abiotrophia defectiva (p=0.011) were enriched in AE, whereas Haemophilus parainfluenzae (p = 0.038) and Prevotella pallens (p = 0.022) were more abundant in Stable. Correlation analyses showed that Candida albicans was positively associated with exacerbation frequency (p < 0.05), while Streptococcus salivarius correlated positively with the oxygenation index. Abiotrophia defectiva was positively associated with Erythrocyte Sedimentation Rate (ESR) and body temperature, but negatively associated with lymphocyte count.

CONCLUSION

Patients in the AE group exhibited altered microbial community structures, and increased fungal colonization may be associated with disease progression, suggesting new targets for clinical intervention.