The role of preoperative antibiotic prophylaxis in the relationship between intestinal colonization and post-ERCP biliary tract infection: a prospective cohort study.

BACKGROUND

Post-ERCP biliary tract infection (PEBTI) is a critical complication influenced by multiple factors, yet the role of preoperative antibiotic prophylaxis remains unclear. This study investigated the relationship between intestinal colonization and PEBTI, and whether antibiotic prophylaxis mediates this association.

METHODS

A multi-center, prospective cohort of 2110 patients undergoing ERCP for biliary obstruction was analyzed. Preoperative rectal swabs screened for common intestinal colonizers. Directed acyclic graphs (DAGs), Cox regression models, inverse probability of treatment weighting (IPTW), and mediation analysis were employed to assess confounders, effect estimates, and mechanistic pathways.

RESULTS

PEBTI occurred in 100 (4.7%) enrolled patients, and intestinal colonization was detected in 343 (16.2%), predominantly ESBL-producing Escherichia coli (73.2%). Initial unadjusted analysis showed a significant association between intestinal colonization and PEBTI (HR = 2.18, 95% CI 1.41-3.36). However, after adjusting for DAG-suggested confounders, the association attenuated to non-significance (adjusted HR = 1.53, 95% CI 0.89-2.66). Mediation analysis revealed no significant indirect effect via antibiotic prophylaxis (HR = 0.93, P = 0.132), accounting for 21% of the observed attenuation. Sensitivity analyses by trimmed-IPTW and stratified center confirmed robustness of findings.

CONCLUSIONS

Our analysis did not find significant evidence that intestinal colonization independently increases PEBTI risk. The observed associations appear to be largely confounded by patient vulnerability factors, with no significant evidence of mediation by antibiotic prophylaxis. These findings suggest prioritizing host-directed prevention strategies over pathogen-directed interventions in clinical practice.