Cultivation-based characterization of biliary microbiota in bile samples collected during routine endoscopic retrograde cholangiography: 10 years of experience at a tertiary center.

INTRODUCTION: Bile has long been considered sterile. Recent studies show that bacteria can frequently be detected in bile and certain bacterial species are associated with bile duct-associated liver disease.

OBJECTIVES: To detect bacterial species and antibiotic resistance in bile in bile duct-associated liver disease.

METHODOLOGY: To evaluate microbiological findings of bile samples obtained during ERCP at a tertiary center from 2009 to 2019.

RESULTS: There were 1885 bile samples from 992 patients examined by cultural microbiological analysis. Germs were detected in 91% of the samples. Most bile samples (n) were obtained from patients who had undergone liver transplantation (LTX; n = 556), followed by patients with primary sclerosing cholangitis (PSC; n = 287). Enterococci were detected in 67% of samples, followed by E. coli (32.2%) and Klebsiella (28.2%). Of 1151 enterococci detected, 13.1% were vancomycin (VRE)s and of 216 staphylococci detected, 10% were ORSA. The proportion of VRE increased with the number of tests performed during ERCPs (P < 0.01; chi-square) and increased 2.5-fold over 10 years, whereas the detection of ORSA remained stable. Patients with cholecystolithiasis were significantly more likely to have evidence of VRE in bile compared to LTX and PSC patients (P = 0.02, P < 0.01; chi-square). The most abundant bacterial genera showed highly statistically significant differences in their levels of liver enzymes and c-reactive protein (P < 0.001).

CONCLUSION: Knowledge of the bacterial composition of bile in various bile duct-associated liver diseases may allow more targeted antibiotic use in the future.