Differences in Non-Pathogenic Lung-Colonizing Bacteria Among Patients with Different Types of Pneumonia: A Retrospective Study.

The clinical impact of non-pathogenic colonizing bacteria in pneumonia remains poorly understood. This retrospective study analyzed the mutual influence of pneumonia and non-pathogenic bacterial flora in the lungs. Bronchoalveolar lavage fluid samples from 483 patients were analyzed using metagenomic next-generation sequencing, and differences in colonizing bacteria in different pneumonia types and their impact on disease prognosis were determined. Patients with bacterial pneumonia exhibited higher and lower colonization rates of Granulicatella adiacens and Streptococcus parasanguinis, respectively, than those without. Fungal pneumonia showed lower and higher colonization rates of Abiotrophia defectiva and Veillonella parvula, respectively; viral pneumonia showed higher colonization rates of Abiotrophia defectiva and Streptococcus mitis. Rothia mucilaginosa was associated with shorter duration of fever, and lower risks of sepsis and multiple organ dysfunction syndrome (MODS). Prevotella melaninogenica was associated with lower risks of sepsis and MODS. These findings suggest that select non-pathogenic bacteria might influence disease severity and also highlight the need for further investigation into microbiome-based therapeutic strategies, potentially guiding personalized pneumonia treatments.