Pseudomonas aeruginosa strains harbouring an unusual blaVIM-4 gene cassette isolated from hospitalized children in Poland (1998-2001)

J Antimicrob Chemother. 2004 Mar;53(3):451-6. doi: 10.1093/jac/dkh095. Epub 2004 Jan 28.


Objectives: During 1997-2001, 151 isolates of imipenem-resistant Pseudomonas aeruginosa were obtained from clinical specimens taken from children hospitalized in Warsaw, Poland. These strains were investigated further to determine the mechanism of resistance.

Methods: The strains were analysed by a combination of genotyping and PCR-based strategies.

Results: Eleven of these strains were found to contain the metallo-beta-lactamase (M beta L) gene bla(VIM-4). The first strain appeared in 1998, and P. aeruginosa strains harbouring this M beta L have become endemic in this hospital since then. All P. aeruginosa strains belonged to serotype O:6, and PFGE analysis revealed four different patterns and three sub-types. All 11 M beta L-producing strains contained an identical class 1 integron with the usual 5' and 3' conserved sequences. The integron included two resistance cassettes, aacA4 in the first position and the bla(VIM-4) cassette in the second position. The bla(VIM-4) gene included an unusual direct repeat of 169 bp of the 3' portion of the bla(VIM-4) gene.

Conclusions: An unusual bla(VIM-4) M beta L has become endemic in P. aeruginosa isolates infecting Polish children hospitalized on surgical wards. The formation of this unusual bla(VIM-4) gene cassette could be explained by a mechanism involving deletion of a segment of an ancestral tandem repeat of bla(VIM-4) via slipped strand replication, mediated by a combination of polymerase and integrase.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Child
  • Drug Resistance, Bacterial
  • Electrophoresis, Gel, Pulsed-Field
  • Gene Transfer Techniques
  • Hospitalization
  • Humans
  • Imipenem / pharmacology
  • Microbial Sensitivity Tests
  • Molecular Sequence Data
  • Poland
  • Pseudomonas Infections / microbiology*
  • Pseudomonas aeruginosa / genetics*
  • Reverse Transcriptase Polymerase Chain Reaction
  • Serotyping
  • Thienamycins / pharmacology
  • beta-Lactamases / genetics*


  • Thienamycins
  • Imipenem
  • beta-Lactamases
  • beta-lactamase bla(VIM-4), Pseudomonas aeruginosa