Characteristics of the gut-lung axis in patients with viral pneumonia and respiratory failure.

Respiratory viral infections can influence the human microbiota, promoting disease progression and complications. The gut-lung axis (GLA), as a critical pathway for microecological regulation and immune modulation, remains poorly understood in terms of its microbial characteristics and role in respiratory failure. The aim of this study was to elucidate the microbial characteristics and functions of the upper respiratory tract and gut and their associations in patients with viral pneumonia complicated by respiratory failure. We included three groups of individuals: healthy controls (HT), viral pneumonia patients without respiratory failure (NRF), and those with respiratory failure (RF), and systematically analyzed the characteristics and associations of the upper respiratory tract and gut microbiota. Beta diversity analysis revealed significant separation of upper respiratory tract and gut microbial communities among the three groups, while alpha diversity decreased with increasing disease severity. LEfSe analysis and correlation analyses targeting complete blood count parameters and serum inflammatory factors revealed synchronous enrichment of Rothia in the upper respiratory tract and Enterococcus in the gut of the RF group. Prevotella was enriched in the gut of the HT group but abnormally increased in the upper respiratory tract of the RF group, reflecting ecological niche shifts. Functional prediction indicated significant enrichment of pathways such as beta-lactam resistance in the RF group. Several genera (such as Blautia and Prevotella) were highly correlated with inflammatory cytokines (IL-1β, IL-6, CRP) and platelet counts, suggesting a microbiota-inflammation-immunity interplay. This study reveals significant dysbiosis of the gut-lung axis in patients with viral pneumonia and respiratory failure, with the Rothia-Enterococcus axis serving as a potential early warning and intervention target. The dynamic changes of the gut-lung microbiota and its association with inflammation and immunity provide a theoretical basis for microbiota-based therapies.