Imipenem-resistance in Serratia marcescens is mediated by plasmid expression of KPC-2

W.-Q. Su, Y.-Q. Zhu, N.-M. Deng, L. Li

Department of Laboratory, Qingdao Municipal Hospital, Qingdao, China. li_li_1212@163.com

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• Pharmacology

OBJECTIVE: Imipenem is a broad-spectrum carbapenem antibiotic with applications against severe bacterial infections. Here, we describe the identification of imipenem-resistant Serratia marcescens in our hospital and the role of plasmid-mediated KPC-2 expression in imipenem resistance.

MATERIALS AND METHODS: We used the modified Hodge test to detect carbapenemase produced in imipenem-resistant strains.

RESULTS: His resistance can be transferred to E. coli in co-culture tests, which implicates the plasmid in imipenem resistance. PCR amplification from the plasmid identified two products consistent with KPC-2 of 583 and 1050 bp that were also present in E. coli after co-culture. The restriction pattern for both plasmids was identical, supporting the transfer from the S. marcescens isolate to E. coli. Finally, gene sequencing confirmed KPC-2 in the plasmid.

CONCLUSIONS: Due to the presence of KPC-2 in the imipenem-resistant S. marcescens, we propose that KPC-2 mediates antibiotic resistance in the S. marcescens isolate.

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