Abstract: Objective To analyse the influencing factors of nosocomial infections and Multi-drug-resistantbacteria (MDRO) infections in elderly patients with malignant tumours, and to provide a scientific basis for the development of effective preventive and control measures. Method 782 malignant tumour patients aged 60 years and above admitted to Shengjing Hospital of China Medical University between June 2016 and January 2023 were selected and divided into no nosocomial infection group(529 cases) and nosocomial infection group(253 cases), of which nosocomial infection included MDRO infection group(156 cases) and non-MDRO infection group(97 cases), and the patients' medical records were reviewed and collected. Multivariate Logistic regression analysis was applied to analyze the indexes with significant differences in the univariate analysis, to assess the impact of nosocomial infection and MDRO infection on the elderly patients. The risk factors of nosocomial infection and MDRO infection in elderly patients with malignant tumours were studied using multifactorial logistic regression analysis. Result The proportions of nosocomial infections and MDRO infections among nosocomial infections in elderly patients with malignant tumours were 32.35% and 61.66%, respectively. The results of univariate analysis showed that there was a statistically significant difference between the two groups of patients in terms of chronic disease, physical weakness, invasive procedures, malignant tumors, hospital stay ≥ 14 days, intensive care unit stay ≥ 1 week, long-term bed rest, and low protein levels (P<0.05)the results of logistic regression showed that: debilitating conditions, invasive operations, malignant tumours, hospital stay ≥14d, intensive care unit stay ≥1 week, and prolonged bed rest were the main risk factors of nosocomial infections and MDRO infections in elderly patients with malignant tumours; chronic diseases, low protein level and low blood pressure were the main risk factors of nosocomial infections in elderly patients with malignant tumours. risk factors; chronic diseases and low protein level were independent risk factors for nosocomial infections; use of ≥3 antimicrobial drugs and antimicrobial application time ≥14d were independent risk factors for MDRO infections. Conclusion The incidence of nosocomial infections and MDRO infections in elderly patients with malignant tumours is high, and their influencing factors are diverse, which must be analysed scientifically and effectively to provide scientific basis for reducing the incidence of infections and improving the therapeutic efficacy and quality of life of patients.

Key words: Pneumonia, Respiratory syncytial virus, Transforming growth factor-β, Interleukin-23, Severity of the disease, Correlation