Retrospective analysis of microbiome in idiopathic pulmonary fibrosis

Abstract

Background: Idiopathic pulmonary fibrosis (IPF) is a well-known life threatening disease, which the progressive lung fibrosis leads to restrictive ventilatory impairment and diffusion failure. While IPF seems to be uncorrelated with infectious subjects, several papers indicated that microbiome composition correlates with progression of IPF. However, the roles of microbiome against respiratory functions and clinical biomarkers in IPF remain unknown. In this study, we examined the relationship between microbial environment in the lung and clinical findings. Methods: Subjects included in this analysis were IPF patients who visited Sapporo Medical University Hospital with approval of the hospital ethics board retrospectively. 16s rRNA were purified from bronchial alveolar lavage fluids obtained at the time of diagnosis and next generation sequencing techniques were used to characterize the bacterial communities. These data were compared with the clinical data of each patients. Results: As a result of sequencing, the most dominant lung phyla were Firmicutes, Proteobacteria and Bacteroidetes. The bacterial diversity was significantly lower in the unstable group, which the decline in forced vital capacity (FVC) was observed during a year. FVC are inversely proportional to the relative abundance of Firmicutes. Also, Streptococcuceae, the largest family OTU in a member of the Firmicutes, was significantly associated with FVC, 6-minute walk distance and serum KL-6. Conclusions: Our study revealed there were some relationships between specific taxa in BALF and clinical findings. Further study of lung microbiome may provide further insights into its possible contribution to IPF pathogenesis and new biomarker.