Objective To investigate the clinical outcome of patients with acute-on-chronic liver failure (ACLF) and bacterial infection on admission after 72 hours of anti-infective therapy and related influencing factors.Methods An electronic database was used to select267 patients with ACLF and bacterial infection on admission who were admitted to the fifth Medical center of Chinese PLA General Hospital from January 2014 to March 2016, and their clinical features were analyzed.According to the outcome after 72 hours of anti-infective therapy, these patients were divided into effective group and ineffective group.The t-test was used for comparison of normally distributed continuous data between two groups, and the Mann-Whitney U rank sum test was used for comparison of non-normally distributed continuous data between two groups.The chi-square test was used for comparison of categorical data between two groups.A logistic regression analysis was used to identify the risk factors for outcome after 72 hours of anti-infective therapy and establish a predictive model, and the receiver operating characteristic (ROC) curve was used to evaluate the diagnostic value of the new model.Results Hepatitis B virus infection observed in 161 patients and alcoholic liver disease observed in 60 patients were the most common causes, and 29 patients experienced septic shock.There were 312 case-times of bacterial infection, with ascites (199 patients) and the lung (77 patients) as the most common infection sites.A total of 49 strains were cultured, among which Escherichia coli (16 strains) and Klebsiella pneumoniae (13 strains) were the most common strains.A total of 20 patients also had fungal infection.Of all patients, 156 (58.4%) had response to anti-infective therapy.Compared with the ineffective group, the effective group had significantly lower incidence rates of acute kidney injury, hepatic encephalopathy, and septic shock, pulmonary infection rate, fungal infection rate, white blood cell count, neutrophil count, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, serum creatinine, international normalized ratio (INR) , and Model for EndStage Liver Disease (MELD) score (all P<0.05) and significantly higher ascites infection rate and prothrombin time activity (both P<0.05) .Compared with the ineffective group, the effective group had significantly lower 30-day mortality rate (15.2%vs 77.5%, χ2=97.942, P<0.001) and 90-day mortality rate (35.2%vs 91.7%, χ2=71.977, P<0.001) .The multivariate logistic regression analysis showed that baseline INR and the presence of septic shock were the risk factors for the outcome of anti-infective therapy.The new predictive model was logistic (p) =-5.907+2.260×septic shock (yes=1, no=0) +1.603×INR.At the cut-off value of-2.3, this model had an area under the ROC curve of 0.746, with a sensitivity of 62.2%, and a specificity of 78.2%.This new model had a higher diagnostic value than MELD score (Delong test, Z=2.402, P=0.016) .Conclusion INR and septic shock were independent influencing factors for predicting the therapeutic outcome of patients with ACLF and bacterial infection after 72 hours of anti-infective therapy.