Biliary microbiota in disease-free, obstructive and post-drainage biliary tracts.

Introduction: Despite years of research, knowledge about the microbial populations of human physiological bile has remained limited. Bile sampling techniques, such as Endoscopic Retrograde Cholangiopancreatography (ERCP), percutaneous biliary drainage, and intra-operative sampling, are invasive procedures typically performed only in the presence or suspicion of biliary tract disease. Furthermore, the increased incidence of bacterial infections following biliary drainage poses a significant clinical concern; however, the relationship between biliary drainage and biliary flora remains poorly understood. In this study, we present a distinct taxonomic composition of bacterial communities identified in bile samples from disease-free individuals, as well as from obstructive and post-drainage biliary tracts. Methods: A metagenomic sequence analysis of bile samples from patients with MBO who underwent percutaneous biliary drainage (PTBD) at our center from 1st May 2021 to 1st March 2022, which were divided into 2 groups, as the MBO group (n = 29) and BD group (n = 27). Eight liver donors were included as a control group. Results: Abundant bacterial populations were detected in the bile of liver donors, revealing a highly similar microbial composition in both disease-free and malignant obstructive biliary trees. Notably, biliary drainage was found to alter the composition of bile microbiota, resulting in decreased microbial diversity and an association with an increase in antibiotic resistance genes. Discussion: These findings provide fundamental knowledge on the composition of the human bile microbiota and present new evidence to support that biliary drainage induces a shift in bile microbiota, rendering it more aggressive and resistant to antibiotics.