The study of genotype and plasmid transfer of carbapenem-resistant Enterobacteriaceae carrying blaNDM-1 with blaIMP-4 or blaKPC-2

Abstract

Objective To analyze the genotype and plasmid transfer of Enterobacteriaceae carring blaNDM-1 with blaIMP-4 or blaKPC-2. Methods From April 2012 to October 2014, a total of 33 non-repeatitive carbapenem-resistant Enterobacteriaceae (including Imipenem-resistant, meropenem-resistant or Ertapenem-resistant) were isolated from 5 hospitals in Wenzhou and Hangzhou. Identification and antimicrobial susceptibility test were performed using Vitek2 Compact automatic microbiology analyzer. Phenotypes of carbapenemase were screened using modified Hodge test and ethylenediamine tetraacetic acid-disk synergy test. Extended spectrum β lactamase test was determined by the double disk combination test which was recommended by Clinical and Laboratory Standards Institute. AmpC activity was tested by a three-dimensional Cefoxitin method. Drug resistant genes including blaNDM-1 and linkage of ISAba125-NDM were detected by polymerase chain reaction (PCR). The purified PCR products were cloned and sequenced. Plasmid conjugation experiment and elimination method were carried out to test partial bacterial strain and K. pneumoniae carrying blaNDM-1 with blaIMP-4 or blaKPC-2. Results Of the 33 non-repeatitive carbapenem-resistant Enterobacteriaceae, 28 were strains of K. pneumoniae, 1 strain of K. oxytoca, 2 strains of Escherichia coli, 1 strain of K. planticola and 1 strain of E. cloacae. Thirteen strains were isolated from Hospital of Sir Run Run Shaw of Zhejiang University, thirteen from Wenzhou Hospital of Traditional Chinese Medicine, one from Wenzhou People's Hospital, three from the First Affiliated Hospital of Wenzhou Medical University and three from Wenzhou Hospital of Integrated Traditional Chinese and Western Medicine. Thirty-one strains were confirmed as carbapenemase-producing with 24 of blaKPC-2, 3 of blaNDM-1, 1 of blaNDM-5 and 3 of blaIMP-4. Among them, one strain carried blaNDM-1 with blaIMP-4 and one strain carried blaNDM-1with blaKPC-2, respectively. The plasmid transfer and conjugation experiment was performed between strains carrying blaNDM-1 and Escherichia coli EC600 or K. pneumoniae ATCC13833 and genes of blaNDM-1 and ISAba125-NDM were obtained. Conclusions blaKPC-2 gene is the popular carbapenemase genotype. blaNDM-1 or blaNDM-5 may be correlated with linkage gene of ISAba125-NDM. Coexistence of blaNDM-1 carrying blaIMP-4 or blaKPC-2 is detected in the same strain, respectively. Enough importance should be attached to the strains, because most of them are multiple drug resistance with related genes located in the plasmid which is easily spread between strains. Key words: Carbapenemase; Enterobacteriaceae; NDM-1; Genotype