Carbapenem-resistant Enterobacteriaceae (CRE) are increasingly identified in children in China. Pediatric intensive care unit (PICU) is the high-risk area. However, data on the epidemiology of CRE in hospitalized children in PICU are limited. The objectives of this study are to characterize the risk factors for colonization or infection with CRE and describe the microbiologic characteristics of pediatric CRE isolates. The investigators will perform a single retrospective study from January 2018 to December 2019 at PICU of Children's Hospital of Fudan University .

The investigators intend to enroll all children who were hospitalized in pediatric intensive care unit PICU of Children's Hospital of Fudan University from January 2018 to December 2019. Children who had positive cultures for any Enterobacteriaceae species before their admission will be excluded. Children with a PICU length of day less than 48h will also be excluded. According to their clinical cultures results, they will be divided into non-CRE、CRE colonization and CRE infection. CRE was defined according to the 2015 Centers for Disease Control and Prevention (CDC) definition as an isolate resistant to imipenem, meropenem, or ertapenem. Clinical and demographic data will be collected from the electronic health record.

Inclusion Criteria:

• All children hospitalized in PICU of Children's Hospital of Fudan University from January 2018 to December 2019.

Exclusion Criteria:

• discharge within 48 hours
• patients had a positive culture for CRE before admission
• incomplete clinical and demographic data

All children hospitalized in PICU of Children's Hospital of Fudan University from January 2018 to December 2019