The bacterial bile microbiome and its role in liver diseases

During the last decade extensive research was done on the human gut microbiome and its relationship to specific diseases. The characterization of the bile microbiome in Primary sclerosing cholangitis (PSC) has been recently published. Still, the bile microbiome is controversially discussed. However, holistic studies characterizing the human bile microbiome and its relationship to liver diseases are still scarce. The aim of the present study was to generate further insights into the composition and activity of the human bile microbiome and its relationships to biliary diseases like e.g. cholangitis, cholestasis, or PSC. For this, we characterized the bile microbiome of patients with PSC, cholangitis, and cholestasis using 16S rDNA sequencing technology and compared their microbiome with those of a control group.

The analysis of the bile microbiome data revealed that the composition of the bile microbiome is totally different than the composition of the microbiome in other compartments like blood, human gut, or ascites. Detailed 16S rDNA microbiome analysis showed that the bile microbiome consists of bacteria belonging to eight different phyla (Actinobacteria, Bacteroidetes, Firmicutes, Fusobacteria, Gemmatimonadetes, Proteobacteria, Saccharibacteria and, Tenericutes). Proteobacteria and in particular Gamma-proteobacteria were the most abundant class of bacteria followed by Firmicutes and here in particular bacteria belonging to the class of Bacilli. The bile microbiome composition differed between patients and controls, alpha-diversity analysis on phylum level revealed that patients with PSC showed a significantly lower alpha-diversity compared to the other tested groups. Furthermore, patients with PSC possessed a less diverse core microbiome in comparison to the controls.

Our results confirm independently recent data on the bile microbiome composition in PSC underscoring the solidity of our results. Moreover, we show that the composition of the bile microbiome differed between patients exhibiting specific biliary diseases, although substantial work is needed to address any causality in their pathogenesis.

Publication History

Article published online:
08 September 2020