Introduction: The 2013 Tokyo guidelines developed a consensus in the antibiotic management of the biliary tract infection through studies evaluating de epidemiology of the bacteria found in bile. However, these recommendations are based on international reports and state the importance of studying the local microbiology, using it to guide de antibiotic treatment. The objective of this study is to describe the characteristics and microbiological profile of patients treated for moderate and severe cholecystitisMaterials and Methods: This is a descriptive study, a case series, describing the characteristics of 131 patients treated in Méderi for moderate and severe cholecystitis, and the isolated bacteria and resistance profile of the bile cultures taken during surgery.Results: Most of the patients had no comorbidities, their average age was 63 years. No difference was found in comorbidities, laboratory test results, presence of biliary obstruction, pancreatitis o the need for prior biliary tract instrumentation, when comparing patients with positive and negative bile cultures. The positivity rate in bile culture was 48%, isolating predominantly enterobacteria. The main isolation was Escherichia coli, follow by Klebsiella y Enterococcus species. The resistance profiles show multisensibility in 93% of cultures, identifying only 4 multidrug resistant bacteria. Discussion: These results reflect those of international reports in terms of bacterial flora, highlighting that our resistance profiles are lower than those reported in other studies, which could lead the way in establishing our local practice guidelines to our own epidemiology, instead of international reports.