Acute cholangitis is a potentially life-threatening condition that requires early empirical antibiotic therapy. In a context of increasing antimicrobial resistance, systematic bile culture sampling during ERCP could optimize antibiotic treatment. The aim of this study is to describe the microbiological profile of acute cholangitis in our setting and to evaluate the clinical impact of bile cultures on therapeutic decision-making.

A prospective, descriptive, observational study was conducted at a tertiary center between 2022 and 2025. Patients diagnosed with acute cholangitis according to the Tokyo Guidelines who underwent ERCP with bile culture were included. Demographic, etiological, microbiological, and antimicrobial treatment variables were collected.

A total of 151 patients were included (57% male). According to the Tokyo classification, 29 (19%) presented with severe, 100 (66%) with moderate, and 17 (13%) with mild cholangitis. Fifty-five percent (55%) had a naïve papilla, 20% had prior ERCP without a stent, and 25% had prior ERCP with a biliary stent. The most frequent etiology was lithiasis (82 patients, 54%), followed by malignant stricture (46 patients, 31%).

Bile cultures were positive in 129 cases (85%); of these, 20% were severe, 67% moderate, and 13% mild cholangitis. Conversely, in patients with severe cholangitis 90% had positive cultures ,in 86% of the moderate, and 77% of the mild.

Most positive cultures were polymicrobial (59%), with a predominance of Gram-negatives (57%), mainly Enterobacteriaceae and enterococci. Other relevant microorganisms were bacteria of the SPICE group found in 32 patients (25%) and Candida in 12 (9%).

The proportion of polymicrobial cultures did not differ significantly among patients with naïve papilla, prior ERCP without stent, and prior ERCP with stent (p>0.05).

Among patients with positive cultures, 92% (119 patients) had received prior antibiotics. Following microbiological results, treatment was modified in 58% of cases (primarily via de-escalation or targeted therapy) and in 42% via escalation or broadening of antibiotic coverage. Blood cultures were obtained in 76 patients with positive bile cultures, resulting positive in 45 (60%) and concordant with bile culture in only 43 cases (57%).

Systematic bile culture collection during ERCP is a simple and efficient procedure, with a high diagnostic yield (85%) and greater sensitivity than blood cultures. Polymicrobial infection is frequent, particularly in patients with prior ERCP, although no significant differences were observed between groups. Bile cultures allow for antibiotic therapy adjustment in a considerable number of patients, both allowing de-escalation and contributing to reduce risk of resistance development and also adjusting therapy in case of resistant or atypical microorganisms.