title: Biliary Mucosal Barrier and Microbiome.
abstract: BACKGROUND
  The biliary system is in continuous contact with the complex microbiota of the intestine. Microbial products have recently been proposed as potential triggers for biliary diseases.
  
  
  METHODS
  The aim of this review is to provide a summary of the current knowledge regarding the role of the biliary and intestinal microbiome in biliary inflammatory diseases.
  
  
  RESULTS
  Previously, it was suggested that the healthy biliary system is a sterile organ, while acute cholangitis and cholecystitis may occur from ascending infections. Although non-inflammatory biliary colonization by certain bacteria such as Salmonella spp. has been already recognized since several decades, human and animal studies indicated only very recently that the gallbladder harbors a complex microbiota also under non-pathologic conditions. Novel findings suggested that - similar to the situation in the intestine - the biliary mucosa features a chemical, mechanical, and immunological barrier, ensuring immunological tolerance against commensals. However, microbial triggers might influence acute and chronic inflammatory disease of the biliary system and the whole liver.
  
  
  CONCLUSIONS
  Although yet undefined, dysbiosis of the biliary or intestinal microbiota rather than a single microorganism may influence disease progression.
authors.affiliation: Department of Internal Medicine III, University Hospital RWTH Aachen, Aachen, Germany.
authors.forename: Julien
authors.initials: J
authors.lastname: Verdier
authors.affiliation: Department of Internal Medicine III, University Hospital RWTH Aachen, Aachen, Germany.
authors.forename: Tom
authors.initials: T
authors.lastname: Luedde
authors.affiliation: Department of Internal Medicine III, University Hospital RWTH Aachen, Aachen, Germany.
authors.forename: Gernot
authors.initials: G
authors.lastname: Sellge
keywords: Bile acids; Cholecystolithiasis; Gallstones; Microbiome; Microbiota; PBC; PSC; Primary biliary cirrhosis; Primary sclerosing cholangitis