Objective To investigate the distribution and antimicrobial resistance of Enterobacter cloacae complex(ECC)isolated from a tertiary hospital in Shanghai.Methods Clinical ECC isolates were collected from 2018 to 2020.Antimicrobial susceptibility test was performed with broth microdilution and agar dilution methods.PCR was applied to detect five carbapenemase genes(blaKPC,blaNDM,blaIMP,blaVIM and blaOXA-48).Results A total of 222 ECC isolates were collected from 2018-2020,including 36 strains(16.2％)from general surgery department.The strains were mainly isolated from sputum(41.0％)and urine(20.3％).MIC results showed that the isolates were highly resistant to trimethoprim-sulfamethoxazole,the second-and third-generation cephalosporins,aztreonam and quinolones(31.1％-71.2％resistant),but low resistance rates to tigecycline,amikacin,mecillinam,and ceftazidime-avibactam(0.5％-9.0％resistant).About 9.5％and 10.4％of the strains were resistant to meropenem and imipenem,respectively.A total of 34 ECC strains were carbapenem-nonsusceptible strains,of which 23 strains were resistant to carbapenems.Among the 34 carbapenem-nonsusceptible strains,25(73.5％)strains were susceptible to mecillinam,including 15 strains producing metallo-β-lactamase.PCR assay identified carbapenemase genes in 21 of the 34 carbapenem-nonsusceptible strains,including blaNDM(14 strains),blaIMP(5 strains)and blaKPC(2 strains).Compared with the strains isolated in 2018,the ECC strains isolated in 2019 and 2020 showed significantly higher resistance rates to imipenem and ceftazidime-avibactam(P＜0.05),primarily associated with the production of NDM.Among the ECC strains resistant to third-generation cephalosporins,20.4％were resistant to imipenem and meropenem,while 4.9％and 8.7％were resistant to amikacin and mecillinam,respectively,and 9.7％were nonsusceptible to tigecycline.Conclusions The ECC isolates in 2019 and 2020 showed increasing resistance rates to carbapenems and ceftazidime-avibactam due to the production of metallo-β-lactamases.Some of the metallo-β-lactamase-producing ECC isolates were susceptible to mecillinam.