Anaerobic infections are very common in clinical practice. Poor control of anaerobic infections in patients undergoing abdominal surgery may lead to the occurrence of complications. The aim of this study is to explore the efficacy and safety of Levornidazole Phosphate Disodium for Injection in the treatment of patients with postoperative intra-abdominal infections caused by anaerobic bacteria.

Inclusion criteria：

Subjects who meet all of the following criteria may be enrolled in the study:

1. Age between 18 and 75 years old
2. Requires minimally invasive surgery (laparoscopic surgery or robotic-assisted surgery), open or percutaneous drainage surgery; Intra-abdominal infection caused by anaerobic bacteria as judged by the investigator, including purulent appendicitis, gangrene perforated appendicitis, periappendiceal abscess, gastric or duodenal perforation or rupture, jejunum, ileum, colorectal perforation or rupture, acute biliary tract infection and liver abscess; and meet at least one of the following two criteria: (1)At least two of the following four conditions must be met within 24 hours before surgery: abdominal pain, tenderness and fever (axillary temperature ≥ 37.5℃); white blood cell count ≥ 10×10^9/L; C-reactive protein above the upper limit of normal; procalcitonin (PCT)above the upper limit of normal;(2) Computed Tomography (CT) or ultrasound confirms the presence of intra-abdominal infection
3. Agree or plan to use the investigational drug for the first time within 24 hours postoperatively
4. The subjects voluntarily underwent the test and signed the informed consent form, and the process of signing the informed consent form was in line with Good Clinical Practice (GCP) guidelines

Exclusion criteria：

Subjects who meet any of the following criteria should be excluded from this study:

1. Those with known or suspected allergies to nitroimidazoles
2. Patients who have participated in other studies and used investigational drugs of other studies within 3 months prior to screening
3. Patients who are taking other medications or have other diseases that may interfere with the evaluation of the safety or effectiveness of the drug; Or patients who are at risk of serious drug interactions due to concomitant medications(such as warfarin, as well as medications with compatibility contraindications to levornidazole, including furbencillin sodium, nafcillin sodium, omeprazole, vorbizole, potassium sodium dehydroandrographolide succinate for injection, azlocillin sodium, etc.)
4. patients who have poor compliance and cannot complete the expected course of treatment and follow-up in the opinion of the investigator
5. Abnormal liver function (alanine aminotransferase (ALT) or aspartate aminotransferase (AST) > 1.5 times the upper limit of the normal value; for patients with acute biliary tract infection or combined liver abscess, it can be relaxed to > 3 times the upper limit of the normal value); or abnormal kidney function (creatinine clearance rate ≤ 60 mL/min/1.73 m² [Cockcroft - Gault formula])
6. Patients with serious primary diseases of important organs and systems such as cardiovascular, nervous system, endocrine system, hematopoietic system (such as heart failure, leukemia, uncontrolled diabetes, etc.), or those with malignant tumors
7. Women during pregnancy or lactation, or women of childbearing age with a positive pregnancy test result before the trial
8. Women of childbearing age and men who cannot take effective contraceptive measures during the trial period. The time limit is from the signing of the informed consent form to 3 months after the last dose
9. Patients with infections other than the abdomen (chronic infections that do not affect the evaluation of intra-abdominal infections [such as chronic rhinitis, chronic pharyngitis, etc.] can be included in this study)
10. Patients with multiple organ failure
11. Those who are considered by the investigator to be severely ill and need to be treated with other broad-spectrum antibiotics with anti-anaerobic effects (except for first/second/third generation cephalosporins, aztreonam, quinolones, aminoglycosides).
12. Those who have received antibiotic treatment within 48 hours before enrollment and randomization(except for single dose)
13. Those with positive test results for hepatitis B surface antigen, acquired immunodeficiency syndrome (AIDS) antibody, treponema pallidum antibody, and hepatitis C antibody
14. Patients with lesions of the brain and spinal cord, epilepsy, organ sclerosis, hematopoietic insufficiency, chronic alcoholism
15. Other patients who are not suitable to participate in this clinical study in the opinion of the investigator