Detection of plasmid-mediated IMP-1 metallo-β-lactamase and quinolone resistance determinants in an ertapenem-resistant Enterobacter cloacae isolate  

作　　者：Li-rong CHEN Hong-wei ZHOU Jia-chang CAI Rong ZHANG Gong-xiang CHEN 

机构地区：[1]Clinical Laboratory Center, the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310009, China [2]Cancer Institute, Zhejiang University, Hangzhou 310009, China

出　　处：《Journal of Zhejiang University-Science B(Biomedicine & Biotechnology)》2009年第5期348-354,共7页浙江大学学报（英文版）B辑（生物医学与生物技术）

摘　　要：Objective： To investigate the mechanism of carbapenem resistance and the occurrence ofplasmid-mediated quinolone resistance determinants qnr and aac（6＇）-Ib-cr in a clinical isolate of Enterobacter cloacae. Methods： An ertapenem-resistant E. cloacae ZY106, which was isolated from liquor puris of a female gastric cancer patient in a Chinese hospital, was investigated. Antibiotic susceptibilities were determined by agar dilution method. Conjugation experiments, isoelectric focusing, polymerase chain reaction （PCR）, and DNA sequence analyses of plasmid-mediated carbapenemases and quinolone resistance determinants were preformed to confirm the genotype. Outer membrane proteins （OMPs） were examined by urea-sodium dodecyl sulfate- polyacrylamide gel electrophoresis （Urea-SDS-PAGE）. Results： Minimum inhibitory concentrations （MICs） of imipenem, mer- openem, and ertapenem for ZY 106 were 2, 4, and 16 pg/ml, respectively. Conjugation studies with Escherichia coli resulted in the transfer of significantly reduced carbapenem susceptibility. ZY106 produced IMP-1 metallo-β-lactamase and CTX-M-3 extended-spectrum β-1actamase, and E. coli transconjugant produced IMP-1. Plasrnid-mediated quinolone resistance determinant qnrS1 was detected in ZY106. Transfer of the qnrSl-encoding-plasmid into E. coli by conjugation resulted in intermediate resistance to ciprofloxacin in E. coli transconjugant. Urea-SDS-PAGE analysis of OMPs showed that ZYI06 lacked an OMP of approximately 38 kDa. Conclusion： It is the first IMP-l-producing Enterobacteriaceae in China and the first report of a clinical isolate that harbors both blalMP and qnrS genes as well. The blalMP-1, blaCTX-M-3, and qnrS1 are encoded at three different plasmids. IMP-1 combined with the loss of an OMP possibly resulted in ertapenem resistance and reduced imipenem and mero- penern susceptibility in E. cloacae.Objective:To investigate the mechanism of carbapenem resistance and the occurrence of plasmid-mediated quinolone resistance determinants qnr and aac(6')-Ib-cr in a clinical isolate of Enterobacter cloacae.Methods:An ertapenem-resistant E.cloacae ZY106,which was isolated from liquor puris of a female gastric cancer patient in a Chinese hospital,was investigated.Antibiotic susceptibilities were determined by agar dilution method.Conjugation experiments,isoelectric focusing,polymerase chain reaction(PCR),and DNA sequence analyses of plasmid-mediated carbapenemases and quinolone resistance determinants were preformed to confirm the genotype.Outer membrane proteins(OMPs) were examined by ureasodium dodecyl sulfatepolyacrylamide gel electrophoresis(Urea-SDS-PAGE).Results:Minimum inhibitory concentrations(MICs) of imipenem,meropenem,and ertapenem for ZY106 were 2,4,and 16 μg/ml,respectively.Conjugation studies with Escherichia coli resulted in the transfer of significantly reduced carbapenem susceptibility.ZY106 produced IMP-1 metallo-β-lactamase and CTX-M-3 extended-spectrum β-lactamase,and E.coli transconjugant produced IMP-1.Plasmid-mediated quinolone resistance determinant qnrS1 was detected in ZY106.Transfer of the qnrS1-encoding-plasmid into E.coli by conjugation resulted in intermediate resistance to ciprofloxacin in E.coli transconjugant.Urea-SDS-PAGE analysis of OMPs showed that ZY106 lacked an OMP of approximately 38 kDa.Conclusion:It is the first IMP-1-producing Enterobacteriaceae in China and the first report of a clinical isolate that harbors both blaIMP and qnrS genes as well.The blaIMP-1,blaCTX-M-3,and qnrS1 are encoded at three different plasmids.IMP-1 combined with the loss of an OMP possibly resulted in ertapenem resistance and reduced imipenem and meropenem susceptibility in E.cloacae.

关 键 词：Antibiotic resistance Carbapenem ENTEROBACTERIACEAE Outer membrane proteins （OMPs） 

分 类 号：Q945.13[生物学—植物学] S859.796[农业科学—临床兽医学]