Profile and mechanism of imipenem resistance in clinical isolates of Serratia marcescens / 中国感染与化疗杂志

ABSTRACT

Objective To investigate the profile and mechanism of imipenem resistance in the clinical isolates of Serratia marcescens. Methods A total of 152 strains of S. marcescens were isolated from January 2013 to December 2014. Disk diffusion method?and?automated?systems?were?used?to?determine?the?susceptibility?of?the?isolates.?The?modified?Hodge?test?and?EDTA?synergy?test?were?employed?to?test?carbapenemase?phenotype.?Agar?dilution?method?in?combination?with?efflux?pump?inhibitor?MC207110?was used to observe the change of imipenem MIC values. The genes encoding carbapenemase, AmpC beta-lactamase and outer membrane protein were detected by polymerase chain reaction. Results? Imipenem?resistance?was?identified?in?87?of?the?152?strains?of S. marcescens.?Modified?Hodge?test?was?positive?for?12?of?the?87?imipenem-resistant?S. marcescens strains. EDTA synergy test was?positive?for?9?of?the?strains.?Imipenem?MIC?was?reduced?to?1/4?to?1/64?in?46?strains?by?agar?dilution?method?in?presence?of?efflux?pump inhibitor MC207110. Five strains were positive for KPC genes, 8 strains positive for IMP gene, and 6 strains positive for DHA gene. Loss of outer membrane protein was found in 16 strains by PCR. Conclusions Imipenem-resistant strains of S. marcescens are?prevalent?in?our?hospital.?KPC,?IMP,?DHA?genes,?and?loss?of?outer?membrane?proteins?and?efflux?pumps?may?all?contribute?to?imipenem resistance in S. marcescens isolates.