Objective:To study the clinical characteristics of patients with severe abdominal infection and the epidemiological characteristics of pathogenic bacteria in a hospital, to provide a basis for rational use of antibiotics and reduce the drug resistance rate of pathogens.Methods:A retrospective analysis was performed on 237 patients with abdominal disease as the primary disease admitted to the surgical intensive care unit (ICU) of the First Affiliated Hospital of Guangxi Medical University from January 1st, 2017 to December 31st, 2019. They were divided into two groups according to whether abdominal infection occurred or not. The clinical features of patients in both groups were analyzed, including gender, age, acute physiology and chronic health evaluation Ⅱ (APACHE Ⅱ) score, chronic underlying diseases, primary abdominal site, abdominal trauma or bleeding, multiple organ dysfunction syndrome (MODS) involving organs and surgical treatment. At the same time, the bacterial origin, bacterial distribution and antibiotics sensitivity test results of patients with abdominal infection were recorded.Results:Abdominal infection occurred in 141 of the 237 patients and did not occur in the remaining 96 patients. There were no statistically significant differences between the abdominal infection group and the non-abdominal infection group in terms of gender, age, chronic underlying diseases, etiology and trauma. The APACHE Ⅱ score in the abdominal infection group was obviously higher than that of the non-abdominal infection group (24.0±8.1 vs. 17.1±5.8, P < 0.01). Incidences of abdominal bleeding, MODS involving four or more organs, surgery and the times of surgery ≥ 3 in the abdominal infection group were significantly higher than those in the non-abdominal infection group (36.2% vs. 17.7%, 20.6% vs. 1.0%, 84.4% vs. 21.9%, 9.3% vs. 0%, all P < 0.05). Among the 141 patients with abdominal infection, 107 obtained positive microbial culture results, and a total of 133 pathogenic strains were detected, including 115 strains of bacteria (86.5%) and 18 strains of fungi (13.5%). The main source of bacteria was abdominal drainage (46.1% of non-bloody specimens and 13.9% of bloody specimens). Among the 115 bacteria, Gram-negative (G -) bacteria were the most common (72.2%) and Gram-positive (G +) bacteria accounted for 27.8%. Escherichia coli and Acinetobacter baumannii were the top two G - bacteria (40.9% and 13.9%, respectively), and enterococcus faecalis accounted for the largest proportion of G + bacteria (7.8%). The pathogenic bacteria of abdominal infection were sensitive to tigacycline. Conclusions:The patients with abdominal infection in our hospital had high APACHE Ⅱ score, more organs failure and were easily complicated with intraperitoneal hemorrhage and required surgical intervention and even repeated surgery. The pathogenic bacteria in patients with abdominal infection in ICU were mainly G - bacteria, and the rate of multi-drug resistance of Acinetobacter baumannii was high. Empirical anti-infective treatment should be started as soon as possible according to the microbial spectrum of the region until the pathogenic bacteria results are obtained. Broad-spectrum antimicrobial therapy and combined antimicrobial therapy are recommended for the healthcare acquired abdominal infection in hospital.