Microbiology of bile in extrahepatic biliary obstruction: A tropical experience

Bile is considered sterile, but in obstructed biliary system, growth of micro-organisms results in bacteraemia and toxaemia. We analysed bacterial profile of patients undergoing endoscopic retrograde cholangiopancreatography (ERCP) and evaluated antibiotic resistance patterns to formulate strategy for antibiotics in patients undergoing ERCP.

Patients with cholestasis who underwent ERCP were enrolled. Bile, collected aseptically, was cultured. Positive cultures were processed for isolate identification and antibiotic susceptibility.

One hundred and sixty-three patients (78 females; mean age - 55.1 ± 15.8 years) were enrolled and divided into two groups: Group I (n = 99) were naïve and Group II (n = 64) had undergone ERCP and stenting previously. Positive culture was seen in 68.1% (n = 111) with monomicrobial growth in 74.8% (n = 83) and poly-microbial growth in 25.2% (n = 28). Culture positivity was common in Group II vis-a-vis Group I (84.4% vs. 57.5%). Poly-microbial growth was significantly more common in Group II (35.2% vs. 15.8%, P = 0.028). Gram-negative bacilli were the predominant organisms isolated with Escherichia coli, Pseudomonas aeruginosa and Klebsiella pneumoniae comprising 70% of the isolates. The most sensitive antibiotics were piperacillin-tazobactam and imipenem. The sensitivity of vancomycin, against Enterococcus spp. was in the range of 60%-70%.

Cholestasis leads to bacterial colonisation in most cases, regardless of the presence of a biliary stent. Biliary stent however predisposes to a polymicrobial growth. Most of the commonly used antibiotics continue to have significant sensitivity and may be used empirically. However, previously stented patients may have a higher incidence of infection with Enterococcus spp. and may require specific therapy.