Antimicrobial exposure is known to reduce the selection for various drug-resistant organisms. Numerous studies have demonstrated the association between antimicrobial use and MDR bacteria detection. However, to the investigators knowledge, there is few data to support the concept that reducing antibiotic use actually leads to improvements in antibiotic susceptibilities. Moreover, antimicrobial stewardship was demonstrated to reduce MDRO and was strongly recommended in clinics. As the investigators know, antimicrobial overuse, which occurs commonly in China, induces a severe antibacterial resistance. China's Ministry of Health (MOH) has established a policy about the antimicrobial stewardship. To date, the investigators do not have published documentation the effects of this policy on multidrug-resistant organism (MDRO) in critically ill patients.

Inclusion Criteria:

• Patients hospitalized in the ICU

Exclusion Criteria:

• Patients who were readmitted to the ICU during a single hospital stay

patients who admitted into intensive care unit