Acute cholangitis (AC) is potentially fatal. Microbiological identification and susceptibility to antibiotics in every Hospital is essential to direct treatment. (1) In our hospital, a third-level cancer hospital, a retrospective, analytical study of 30 patients undergoing endoscopic retrograde cholangiography with AC and positive biliary culture (BC) was performed over a period of 6 months. We found that 90% of BC were monomicrobial, with E. coli in more than half of these patients (55%). It is worth mentioning that 27% of the strains were extended-spectrum beta-lactamase-producing Escherichia coli (ESBL). In the susceptibility analysis we found that 78% were sensitive to carbapenems, 66% to aminoglycids and 44% to piperacillin-tazobactam. Pseudomoas aeruginosa was found in 15% of the BC, but only 40% were sensitive to carbapenems. Despite the similarities of this cohort with other studies (1) (2) (3) (4) (5) it is worth mentioning that we found a high proportion of E.coli-ESBL and P.aeruginosa. Is important to mention that these patients had history of hospitalization (3 months), previous use of antibiotics, previous instrumentation of the bile duct, albumin <3.5g/dl and moderate AC (1). With the findings of this cohort, we considered that being a specialized hospital with oncologic patients with previous hospitalizations and previous medical and endoscopic interventions may contribute to find aggressive bacteria in the cultures so initial antimicrobial treatment should consider broad spectrum antibiotics with coverage for these microorganisms.