Biliary tract microbiota: a new kid on the block of liver diseases?

The microbiome plays a crucial role in maintaining the homeostasis of the organism. Recent evidence has provided novel insights for understanding the interaction between the microbiota and the host. However, the vast majority of such studies have analyzed the interactions taking place in the intestinal tract. The biliary tree has traditionally been considered sterile under normal conditions. However, the advent of metagenomic techniques has revealed an unexpectedly rich bacterial community in the biliary tract. Associations between specific microbiological patterns and inflammatory biliary diseases and cancer have been recently described. Hence, biliary dysbiosis may be a primary trigger in the pathogenesis of biliary diseases. In particular, recent studies have suggested that microorganisms could play a significant role in the development of gallstones, pathogenesis of autoimmune cholangiopathies and biliary carcinogenesis. Moreover, the intimate connection between the biliary tract, liver and pancreas, could reveal hidden influences on the development of diseases of these organs. Further studies are needed to deepen the comprehension of the influence of the biliary microbiota in human pathology. This knowledge could lead to the formulation of strategies for modulating the biliary microbiota in order to treat and prevent these pathological conditions.