At present, carbapenem-resistant Enterobacteriaceae (CROs) infections are a global challenge. The use of antibiotics, proton pump inhibitors, and vasoconstrictors in the intensive care unit (ICU), as well as the disease state, have a significant impact on the intestinal flora and may also have a significant impact on the pulmonary microecology, which is unfavorable for the long-term prognosis of patients. The study of pulmonary microecology is currently a hot topic, but it is not clear whether intestinal flora disorders promote pulmonary microecological disorders. Therefore, it is also unclear whether intestinal flora disorders in patients with severe CRO infections have an impact on pulmonary microecological disorders. This project aims to first study the differences in intestinal flora and pulmonary microecology between patients with pulmonary CRO infections and those without CRO infections, as well as the correlation between intestinal flora disorders and pulmonary microecology. Fecal microbiota transplantation (FMT) is a therapeutic approach that involves transplanting the functional intestinal microbiota from healthy individuals into patients to restore an imbalanced intestinal microbiota and treat intestinal and extra-intestinal diseases. Studies have shown that FMT has a positive effect on the clearance of CROs colonization and the prevention of infection in non-ICU patients. Over the past decade, FMT has made breakthrough progress in the treatment of intestinal and extra-intestinal diseases, bringing disruptive new strategies for the treatment of difficult intestinal and extra-intestinal diseases. These results suggest that FMT not only helps to restore a healthy intestinal microbiota but may also reduce the occurrence of recurrent infections by inhibiting the competition of drug-resistant bacteria. Given that CROs in the intestinal microbiota are an important source of enterogenic infections and hospital-acquired bloodstream infections and pneumonia, this project aims to further conduct a randomized controlled clinical study, including critically ill patients with MDROs infections admitted to the ICU, who can be evaluated to discontinue antibiotics and have food intolerance syndrome. FMT will be administered through a nasojejunal tube to improve the imbalance of the intestinal microbiota caused by broad-spectrum antibiotics and other disturbances, and to study the promoting effect and safety of FMT on the recovery of pulmonary microecological imbalance in critically ill patients, as well as to evaluate its impact on ICU stay, ICU mortality, in-hospital mortality, and 28-day mortality.