Bacterial Strains

This retrospective study was performed in the First Affiliated Hospital of Chongqing Medical University, a 3200-bed tertiary hospital located in Southwest China. A total of 892 clinical K. aerogenes strains were isolated and identified from January 2012 to December 2018 by using the VITEK2 compact or VITEK MS (bioMerieux, Hazelwood, MO, United States) automated system at the department of laboratory medicine, among which 36 strains were resistant to at least one carbapenem on the basis of antimicrobial susceptibility testing results determined by the broth microdilution method, with the criteria of MIC of ≥2 mg/L for ertapenem, ≥4 mg/L for imipenem, and ≥4 mg/L for meropenem; and 5 strains were intermediate to at least one carbapenem, with the criteria of MIC of = 1 mg/L for ertapenem, = 2 mg/L for imipenem, and = 2 mg/L for meropenem (Supplementary Figure 1). Only the first isolate from each individual patient was included in this study.