Characterization of a new integron containing bla(VIM-1) and aac(6')-IIc in an Enterobacter cloacae clinical isolate from Greece

J Antimicrob Chemother. 2005 May;55(5):634-8. doi: 10.1093/jac/dki073. Epub 2005 Mar 10.

Abstract

Objectives: A clinical isolate of Enterobacter cloacae exhibiting reduced susceptibility to imipenem and a positive EDTA-disc synergy test was studied for carbapenemase production.

Materials and methods: MICs were determined with standard procedures as well as using a higher inoculum. Isoelectric focusing of cell extracts was used for detection of beta-lactamases. PCR assays with primers specific for the bla(VIM) gene and the conserved segments of class 1 integrons and sequence analyses were carried out to identify the gene and to map the metallo-beta-lactamase encoding integron. Transferability of the gene was assessed with conjugation experiments using the filter mating technique. To identify the location of the bla(VIM-1) gene, Southern hybridization was carried out in genomic DNA using an internal fragment of the bla(VIM-1) gene as a probe, amplified by PCR.

Results: The isolate was resistant to extended-spectrum beta-lactams. The MICs of carbapenems were below the resistance breakpoints but rose above resistance breakpoints when an inoculum of 10(8) cfu/mL was used. Isoelectric focusing detected a beta-lactamase with a pI of 6.1, which exhibited imipenem-hydrolysing activity in a microbiological assay. Ceftazidime and imipenem resistance were not transferable by conjugation. PCR assays identified the bla(VIM-1) gene in the variable region of a class 1 integron which also carried the aac(6')-IIc gene. The bla(VIM-1) probe hybridized with an approximately 130 kb fragment of genomic DNA, suggesting a chromosomal location of the gene.

Conclusion: We describe a novel class 1 integron containing bla(VIM-1) and aac(6')-IIc genes in an E. cloacae clinical isolate.

MeSH terms

  • Acetyltransferases / genetics*
  • Acetyltransferases / metabolism
  • Aged
  • Amino Acid Sequence
  • Bacteremia / microbiology
  • DNA, Bacterial / analysis
  • Drug Resistance, Multiple, Bacterial
  • Enterobacter cloacae / drug effects*
  • Enterobacter cloacae / enzymology
  • Enterobacter cloacae / genetics
  • Enterobacter cloacae / isolation & purification*
  • Enterobacteriaceae Infections / microbiology
  • Ertapenem
  • Greece
  • Humans
  • Imipenem / pharmacology
  • Integrons / genetics*
  • Lactams / pharmacology
  • Male
  • Microbial Sensitivity Tests
  • Molecular Sequence Data
  • Polymerase Chain Reaction
  • beta-Lactamases / genetics*
  • beta-Lactamases / metabolism
  • beta-Lactams / pharmacology*

Substances

  • DNA, Bacterial
  • Lactams
  • beta-Lactams
  • Imipenem
  • Acetyltransferases
  • VIM-1 metallo-beta-lactamase
  • beta-Lactamases
  • Ertapenem

Associated data

  • GENBANK/AY648125