Abstract: Objective To investigate the drug resistance phenotype of carbapenems resistance in Serratia marcescens strains. Methods From June 2018 to September 2019, 235 non-repetitive strains of Serratia marcescens were isolated from patients in Gulou Hospital affiliated to Medical College of Nanjing University. The drug sensitivity was detected by Vitek 2 Compact matched GN13 drug sensitivity board and disk diffusion method. The carbapenem phenotype was screened by modified carbapenem inactivation test（mCIM）and EDTA- modified carbapenem inactivation test（eCIM）. The carrying status of carbapenem gene was detected by PCR and sequencing analysis. Results Among 235 strains of Serratia marcescens, 53 strains（22.6%）were resistant to both meropenem and imipenem. Among the 53 carbapenem resistant strains, 23（43.4%）were sensitive and 21（39.6%）were intermediate to ceftazidine. The resistance rates to ceftriaxone, amtronan, ciprofloxacin and levofloxacin were more than 98%, and the resistance rates to amikacin and cotrimoxacin were 1.7% and 1.6%, respectively. All of them were positive for mCIM and 3 strains were positive for eCIM. Among the 53 strains, 51 strains had bla_KPC-2 gene, 1 strain had bla_NDM-1 gene, 1 strain carried both bla_KPC-2 andbla_NDM-1 genes, and no bla_IMI, bla_OXA48, bla_FOX, bla_IMP and bla_VIM genes were detected. Conclusion The detection rate of carbapenem-resistant Serratia marcescens was high in our hospital. Bla_kpc-2 gene is the main prevalent genotype in carbapenem-resistance in Serratia marcescens strains.

Key words: Serratia marcescens strains, Carbapenems, Drug resistance