Real-World Effectiveness of Aztreonam-Avibactam Against MBL-Producing CRE

Why This Study is Needed Some bacterial infections have become resistant to common antibiotics, making them very difficult to treat. This is a growing and serious health problem. A new combination drug, Aztreonam-Avibactam (we'll call it ATM-AVI), has been developed to fight these tough bacteria. This new drug was recently approved for use in Europe (April 2024), the United States (February 2025), and China (June 2025). Because it is so new, there is very little information available, especially in China, on how well it works for real patients outside of initial testing. This lack of real-world experience means we don't know enough about: * How effective it is for typical patients in China. * The types of patients and infections it is used for. * How it affects a patient's time in the hospital. This study aims to fill these gaps by looking at how ATM-AVI performs in Chinese hospitals, which will help doctors better treat these dangerous infections and improve patient recovery. What the Study Aims to Find Out Main Goal: To see how well ATM-AVI works for adult patients in China with these specific antibiotic-resistant infections. Other Goals: To gather more details about: * How patients are responding to the treatment at different points (e.g., after 5 days, at the end of treatment, and at a follow-up check). * Whether the bacteria causing the infection are cleared. * How the treatment affects the patient's hospital stay and use of resources. * The number of patients who, unfortunately, pass away during or after treatment. * The characteristics of the patients (like age) and their infections. * How doctors are using this new drug and if it's used alongside other antibiotics. How the Study Will Work This is an observational study that will be conducted in about 30 hospitals across China. We plan to include around 100 adult patients who were hospitalized with these tough infections and received the new drug, ATM-AVI, for at least one full day. The study will run from October 2025 to June 2027. We will look at both past (retrospective) and future (prospective) patients. For past patients, we will review their existing medical records. For future patients, we will ask for their permission (informed consent) before collecting any information. We will collect information from patient records, such as: * Basic patient details and the nature of their infection. * How and when the ATM-AVI drug was used. * Details about their hospital stay. * The results of their lab tests. A doctor will assess and record how each patient is doing at key points: 5 days after starting the drug, at the end of the treatment, and at a follow-up check to see if the infection is cured.