During liver transplantations gut microbiota may infiltrate the biliary system. This can lead to postoperative polymicrobial infections and thus cholangitis, suspected to result from bacterial colonization of bilioenteric catheters as well as by immunosuppressive treatment. Cholangitis can lead to systemic, life-threatening infections such as sepsis or organ failure. Therefore, understanding the dynamics of polymicrobial biofilms on bilioenteric catheter is of high importance.

The most prevalent families of microorganisms found in biofilms on biliary catheters are gram-positive Enterococcaceae and gram-negative Enterobacteriaceae. Enterococcaceae are less abundant than Enterobacteriaceae in the biofilms but have an equivalent tendency to be isolated from cholangitis patients – suggesting that potentially pathogenic Enterococcaceae may be sustained within mixed bilioenteric catheter biofilms by interactions with Enterobacteriaceae.

This study therefore aimed to elucidate the inter- and intraspecies communication between representative isolates of Enterococcaceae and Enterobacteriaceae isolated from bilioenteric catheters, in a standardized in vitro system. We investigate spatial and temporal changes in biofilm structure and composition using microscopy and viability staining, colony forming units (CFU) counting and 16S rRNA gene sequencing for microbiome analysis. We determined how the microbial dynamics of polymicrobial interaction changed between Enterococcaceae and Enterobacteriaceae comparing planktonic to biofilm growth on various catheter materials. Additionally, we investigated the influence of intrinsic factors such as antibiotic resistance genes or external factors such as bile acids and antibiotics on these dynamics. Furthermore, we use bioinformatical tools to explore the microbial dynamics of polymicrobial interaction Enterobacteriaceae and Enterococcaceae at a genetic level in clinical samples and reconstituted lab microbiomes.

This multifaceted approach aims to provide insight into the mechanisms of polymicrobial biofilm formation in the biliary system and identify potential interventions to mitigate postoperative complications in patients.