A multicenter, retrospective, real-world stduy . Subjects with composite criteria were teated with eravacycline ,and 100 cases ,Tigecycline and 300 cases were to be enrolled.

The study is a multicenter, retrospective, real-world study, through retrospective collection of cases of gram-negative bacterial infections in the First Affiliated Hospital of Nanjing Medical University, Nanjing Drum Tower Hospital, Nanjing First Hospital, Shaw Hospital Affiliated to Nanjing Medical University, Affiliated Hospital of Xuzhou Medical University, and Xuzhou Central Hospital, and 100 cases of eravacycline,300 cases of tigecycline are planned to be enrolled.

Inclusion Criteria:

Bacteriological results show drug-resistant Gram-negative bacteria Use of new tetracycline drugs for ≥72 hours Age ≥18 years

Exclusion Criteria:

Advanced tumors Severe immunodeficiency or mental illness Severe liver and kidney dysfunction Pregnant or breastfeeding women Rejection Criteria: None

Data acquisition:

General condition: age, gender, acute physiology and chronic health status score (APACHEII), endotracheal intubation/tracheostomy, site of infection, course of treatment, presence of other pathogens, concomitant use of other antibiotics, and ICU admission; Specimen source: blood/respiratory/other; Drug-resistant pathogens: Acinetobacter baumannii/Klebsiella pneumoniae/Escherichia coli; Evaluation of clinical efficacy and bacterial efficacy during treatment with eravacycline and tigecycline; Common adverse reactions in eravacycline or tigecycline therapy; Treatment options Recommended dose of eravacycline : calculated according to the patient's weight, intravenous infusion at 1mg/kg, q12h, the infusion duration is not less than 60 minutes, and the recommended course of treatment is 4-14 days. The investigator can adjust the specific medication regimen according to the severity and location of the patient's infection and the patient's clinical response.

Recommended dose of tigecycline is 100 mg as a loading dose and 50 mg every 12 hours as a maintenance dose, and for multidrug-resistant infections, a high-dose tigecycline 200 mg as an initial dose and a maintenance dose up to 100 mg every 12 hours.

Inclusion Criteria:

Bacteriological results show drug-resistant Gram-negative bacteria Use of new tetracycline drugs for ≥72 hours Age ≥18 years

Exclusion Criteria:

Advanced tumors Severe immunodeficiency or mental illness Severe liver and kidney dysfunction Pregnant or breastfeeding women

Patients with infections clinically caused by drug-resistant gram-negative bacteria (other than CRPA) and treated with eravacycline and tigecycline