Objective:To identify risk factors for infections by multidrug-resistant organisms(MDRO)in elderly patients admitted to the intensive care unit(ICU)based on an retrospective analysis of data from the Medical Information Mart for Intensive Care-Ⅳ v2.0(MIMIC-Ⅳ v2.0).Methods:Structured query language was used to extract basic information, disease severity scores, laboratory test results, medications, medical procedures, and outcome events of elderly patients from MIMIC-Ⅳ v2.0.Patients were divided into a non-MDRO group and an MDRO group based on whether they had MDRO infections.Univariate analysis was performed according to the type of variables.For significant variables identified from univariate analysis, logistic regression was used to calculate the odds ratio and the 95% confidence interval for MDRO infections.The Kaplan-Meier method was used to draw survival curves.The log-rank test was used to analyze the 28-day survival rate.Results:A total of 31 237 cases were enrolled, including 26 032 with non-MDRO infections and 5 205 with MDRO infections.The MDRO infection rate was 16.7%.MDRO were most frequently found in urine cultures, and the most common bacteria belonged to the genus Enterobacter.Multivariate logistic regression analysis showed that age( P=0.006), being male( P<0.001), coronary artery disease( P<0.001), brain disease( P=0.042), hemoglobin( P<0.001), albumin( P<0.001), and mechanical ventilation( P<0.001)were protective factors against MDRO infections.Diabetes( P<0.001), COPD( P<0.001), chronic kidney disease( P<0.001), white blood cell( P=0.001), SAPS Ⅱ( P<0.001), previous use of antibiotics( P<0.001), use of proton pump inhibitors( P<0.001), glucocorticoids( P<0.001), immunosuppressants( P<0.001)and sedatives( P<0.001), and continuous renal replacement therapy(CRRT)( P=0.015)were risk factors for MDRO infections.The 28-day mortality rates of the non-MDRO and MDRO groups were 16.3% and 19.1%, respectively.The log-rank test showed that the difference between two groups was statistically significant( P<0.001). Conclusions:The mortality rate among patients with MDRO infections is higher than among those with non-MDRO infections.Previous use of antibiotics, use of proton pump inhibitors, glucocorticoids, immunosuppressants and sedatives, mechanical ventilation, and CRRT are risk factors for MDRO infections.