ABSTRACT
Objective:To investigate the resistance and transmission mechanism of carbapenem-resistant Enterobacterales (CRE), so as to provide the scientific evidence for the treatment and prevention of CRE infection.Methods:Seventy-six isolates of CRE isolated from Shaoxing Second Hospital between May 2016 and August 2018 were included. The isolates were re-identified by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). The minimum inhibitory concentrations (MICs) of colistin, tigecycline, ceftazidime-avibactam, fosfomycin and other antibacterial drugs were determined using broth microdilution or agar dilution methods. PCR and sequencing analysis were performed to detect carbapenemase encoding genes ( blaKPC, blaNDM, blaIMP, blaVIM, blaOXA-48). Pulsed field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) were used to analyze homology of strains. S1-PFGE combined with Southern blot hybridization were used to locate the carbapenamase genes. Filter mating test were performed to determine the horizontal transfer ability of plasmids harboring carbapenamase genes. Results:Among the 76 isolates of CRE, 51 isolates were Klebsiella pneumoniae; 10 isolates were Escherichia coli; 15 isolates were other Enterobacterales. The 76 CREs were mainly isolated from urine, sputum and blood samples. The distribution rate of ICU was the highest (55.26%). The 76 CREs showed low resistance rates (0%, 1.33%, 18.42%) to colistin, tigecycline and ceftazidime-avibactam. The resistance rates to amikacin and fosfomycin were <45%, and the resistance rates to other drugs were >97%. The detection rate of KPC-2 carbapenemase was the highest (85.33%). The ST11 CRKP producing KPC-2 carbapenemase accounted for the highest proportion (62.75%), mainly distributed in the ICU (62.50%). Southern blot hybridization showed that blaKPC-2 was mainly located on a plasmid about 90 kb (39/63). Filter mating test showed that blaKPC, blaNDM and blaIMP could be transferred horizontally to recipient bacteria through plasmids. Conclusions:The 76 CRE isolates were only susceptible to a few antibacterial drugs, such as colistin, tigecycline and ceftazidime-avibactam. The production of KPC-2 carbapenemase was the main reason for the resistance of Enterobacterales to carbapenems. KPC-2 carbapenemase-producing ST11 Klebsiella pneumoniae was the main epidemic clone of carbapenem-resistant Klebsiella pneumoniae (CRKP). The 90 kb size plasmid was the main plasmid encoding blaKPC-2 gene. Carbapenemase genes can be transferred horizontally through plasmids. The hospital should strengthen prevention of nosocomial infections to control the clonal prevalence of CRE.