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 <i>Granulicatella adiacens</i> and <i>Streptococcus parasanguinis</i>, respectively, than those without. Fungal pneumonia showed lower and higher colonization rates of <i>Abiotrophia defectiva</i> and <i>Veillonella parvula</i>, respectively; viral pneumonia showed higher colonization rates of <i>Abiotrophia defectiva</i> and <i>Streptococcus mitis</i>. <i>Rothia mucilaginosa</i> was associated with shorter duration of fever, and lower risks of sepsis and multiple organ dysfunction syndrome (MODS). <i>Prevotella melaninogenica</i> 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.