Microbiological study and antimicrobial susceptibility of bile in biliary therapeutic endoscopy.

Background: Biliary obstruction together with bacterial colonization of the bile duct may lead to development of acute cholangitis. The reported incidence of infectious complications may reach up to 10%. Nevertheless, no antibiotic prophylaxis is administered routinely, prior to endoscopic therapeutic procedures.

Aim: To investigate the presence and degree of biliary bacterial colonization during endoscopic retrograde cholangiopancreatography (ERCP) in patients with biliary obstruction. Furthermore, we evaluated antibiotic therapy regimens, which would cover the bacterial species obtained by ERCP and subsequent culture in each patient.

Methods: Forty-four patients with biliary obstruction who underwent an ERCP with biliary drainage were prospectively included. The primary indication of ERCP was choledocholithiasis (48%), followed by benign biliary strictures (32%) and malignant bile duct obstruction (18%). Bile cultures were obtained by means of bile aspiration via the cannulation catheter. Aerobic and anaerobic cultures were prepared from all obtained specimens and the isolated organisms were identified. In the case of positive cultures, an in-vitro resistance test for different antibiotics was performed.

Results: The overall positive rate of bile culture was 93%. The organisms cultured were Escherichia coli (26.8%), Enterococcus (17%), Klebsiella (14.6%), Enterobacter (14.6%) and Pseudomonas (9.7%) in decreasing order. In-vitro testing of different antibiotics was carried out in these 41 isolates. Imipenem showed the best antimicrobial activity (sensitivity, 100%), followed by colistin (94%), tobramycin (93%), amikacin (89.6%), gentamycin (85.2%) and ceftazidin (82%). Amoxicillin/clavulanic acid and ofloxacin were less sensitive (66% and 60% respectively). Ceftazidin was the most effective antibiotic on Escherichia coli (sensitivity 83%). Multi-resistant organisms were noted in 22% of the cases.

Conclusions: Escherichia coli was found to be the pathogen most frequently detected in bile following endoscopic interventions in the biliary tract. Enterococci and Klebsiella were found in bile cultures with an incidence exceeding 10%. In view of the in-vitro test results, amoxicillin/clavulanic acid or quinolons are not suitable antibiotics for the prophylaxis of biliary infections. Moreover, Gram-positive bacteria such as Enterococcus are emerging as causative microorganisms. If these organisms are isolated, antimicrobial drugs should be replaced by narrower-spectrum antimicrobials.