Pulmonary infection is a kind of infectious disease that seriously damages human health. It usually starts quickly and progresses rapidly in clinical manifestations, and is often accompanied by upper respiratory tract infection symptoms. With the increasing use of broad-spectrum antibiotics in clinical practice, the failure of anti-infection caused by drug-resistant bacteria is more and more common. Once a patient develops carbapenem-resistant gram-negative bacteria (CRO) infection, there are limited drug options. Therefore, HAP, as a serious and common complication, has a high incidence and mortality for ICU patients. In this study, patients who met the diagnostic criteria for pulmonary infection caused by CRO that was clearly or strongly suspected to be resistant to carbapenems but sensitive to CMS were selected, and the combined treatment regimen of CMS intravenous atomization was adopted. To explore the therapeutic effect of CMS combined with intravenous atomization in patients with carbapenem resistant gram-negative bacteria in lung infection. To evaluate the safety and tolerability of the combination regimen in patients with pulmonary infections caused by CRO. The purpose of this study was to explore the efficacy and safety of CMS combined with intravenous atomization in the treatment of patients with CRO induced pulmonary infection, and to provide a basis for its clinical rational application.

Inclusion Criteria:

1. Voluntarily participate in the study and sign the informed consent;
2. Inpatients aged 18-80 years old, regardless of gender;
3. Patients who met the diagnostic criteria for pulmonary infection in the Guidelines for the Diagnosis and Treatment of Hospital-Acquired Pneumonia and Ventilator-Associated Pneumonia for Adults in China (2018 Edition);
4. Infections caused by Gram-negative bacteria (CRO) that are known or strongly suspected to be resistant to carbapenems but sensitive to CMS.

Exclusion Criteria:

1. Age > 80 years old;
2. The patient had a history of severe allergy or hypersensitivity to polymyxins;
3. Patients with serious dysfunction of heart, liver, kidney and other important organs;
4. Patients with serious diseases such as malignant tumors and blood system diseases;
5. Patients with low immune function and risk of opportunistic pathogen infection;
6. Patients who used excessive colistin intravenous or atomized inhalation therapy within 72h before enrollment;
7. Have participated in other clinical trials within three months;
8. Pregnant or breastfeeding women;
9. There are other circumstances that the researcher believes are not suitable for inclusion.