Objective To investigate the pathogenic bacterial characteristics and influen-cing factors for bile infection in acute biliary pancreatitis (ABP).

Methods The retrospective case-control study was conducted. The clinical data of 180 ABP patients who were admitted to Ningxia Medical University General Hospital from January 2020 to January 2023 were collected. There were 90 males and 90 females, aged (55±17)years. All patients underwent endoscopic retrograde cholangio-pancreatography (ERCP) and bile cultures were collected for testing. Observation indicators: (1) distribution of pathogen in the infected bile and drug resistance of major pathogen; (2) analysis of factors influencing bile infection in ABP patients. Count data were expressed as absolute numbers and percentages. Univariate analysis was conducted using the chi‑square test or independent sample t test, and multivariate analysis was conducted using the Logistic regression model.

Results (1) Distribution of pathogen in the infected bile and drug resistance of major pathogen. Of the 180 ABP patients, intraoperative bile cultures obtained during ERCP were positive of pathogen in 64 patients, yielding a positivity rate of 35.56%(64/180). Of the 64 patients with positive of pathogen in bile cultures, 52 cases showed single‑pathogen infection and 12 cases showed mix‑pathogen infection. A total of 74 non‑duplicate isolates were recovered from 64 patients, including 40 Gram‑negative bacteria, 30 Gram‑positive bacteria, and 4 fungi. Among the Gram‑negative bacteria, 22 strains of Escherichia coli showed drug resistance rates exceeding 70% to ceftriaxone, cefuroxime, ceftazidime, piperacillin, and ampicillin/sulbactam. Ten strains of Citrobacter freundii showed drug resistance rates exceeding 50.0% to ceftriaxone and ceftazidime. Eight strains of Klebsiella pneumoniae showed drug resistance rates exceeding 70.0% to ceftriaxone, cefuroxime, ceftazidime, piperacillin, ticarcillin, trimethoprim/sulfamethoxazole, levofloxacin, and nitrofurantoin. Among the predominant Gram-positive bacteria, 18 strains of Enterococcus faecalis showed drug resistance rates of 77.8%(14/18) to penicillin, ampicillin, and ciprofloxacin. Eight strains of Enterococcus faecium showed drug resis-tance rates of 37.5%(3/8) to streptomycin, gentamicin, tetracycline, and penicillin. (2) Analysis of factors influencing bile infection in ABP patients. Results of multivariate analysis showed history of ERCP, history of cholecystectomy and pancreatic necrosis were independent risk factors influencing bile infection in ABP patients (odds ratio=3.25, 2.90, 3.16, 95% confidence interval as 1.17-8.98, 1.17-7.19, 1.27-7.87, P<0.05).

Conclusion The main pathogens causing bile infection in ABP patients are bacteria. History of ERCP, history of cholecystectomy and pancreatic necrosis are independent risk factors influencing bile infection in ABP patients.