Emergence of carbapenem-hydrolysing metallo-beta-lactamase VIM-1 in Pseudomonas aeruginosa isolates in France.

Recent articles in CMI have described the dissemination of metallo-b-lactamase (MBL) genes conferring resistance to carbapenems [1,2]. Carbapenem-hydrolysing b-lactamases identified in Pseudomonas aeruginosa have mostly been of the IMP and VIM families [3]. Although VIM-1 was the first determinant described in Europe (in Italy), VIM-2 determinants have spread worldwide and have been reported in isolates causing outbreaks of infection [4]. We wish to report the first isolation in France of P. aeruginosa isolates producing the VIM-1 type MBL. A prospective study was carried out among a collection of 1400 P. aeruginosa isolates recovered from 105 French hospitals during 2004–2005. Twenty-three isolates exhibited resistance to ticarcillin, associated with resistance to ceftazidime or imipenem, but only four were recognised as MBL producers using Etest strips for MBL detection (AB Biodisk, Solna, Sweden) [3]. Isolates V4 (Saint Germain-en-Laye) and P0510 (Nantes) were from urine, whereas V115 (Le Mans) and V1236 (Vannes) were from bronchial aspirates. MICs were determined by agar dilution and interpreted as recommended by CLSI guidelines [5], with P. aeruginosa VR-143 ⁄ 97 (VIM-1-positive) as a reference strain [6]. All four isolates were resistant to all available antibiotics, except colimycin, fosfomycin, amikacin and aztreonam. PCR with blaVIMand blaIMP-specific primers, followed by sequencing, revealed an identical blaVIM-1 gene in each MBL-positive isolate [7]. PCR mapping [8] and sequencing of the flanking regions revealed an integron, In70.2, which was identical to that found in the four P. aeruginosa isolates described by Lauretti et al. [6]. Conjugation experiments [7], using the four VIM-1-producing isolates as donors, failed to yield transconjugants. To search for a possible chromosomal location of the MBL gene, the I–CeuI endonuclease technique was used [9]. The internal blaVIM-1 probe hybridised with a very large fragment that co-hybridised with the 16S rRNA probe, indicating a chromosomal location for the blaVIM-1 gene, as reported previously for P. aeruginosa VR-143 ⁄ 97 [6]. Pulsed-field gel electrophoresis analysis was also performed in order to genotype the four VIM-1-positive isolates [4]. Although V4, V115 and V1236 had been recovered from different hospitals located at least 200 km from each other, these isolates were clonally related, while isolate P0510 belonged to a distinct clone. Pulsed-field gel electrophoresis analysis also indicated that those two pulsotypes were different from that of the P. aeruginosa VR143 ⁄ 97 strain from Italy [6]. VIM-1 is the second MBL (after VIM-2) that has been identified as a cause of carbapenem resistance in P. aeruginosa isolates in France. In nearby European countries (Greece and Italy), VIM-1 is predominant and has been associated with large outbreaks of multidrug-resistant P. aeruginosa or Enterobacteriaceae [3]. In Spain, following the discovery of VIM-2 in P. aeruginosa, strains of Escherichia coli and Klebsiella pneumoniae producing VIM-1 have recently been isolated [3]. Thus, VIM-1 and VIM-2 may coexist in southern Europe in P. aeruginosa strains. Interestingly, the genetic structure surrounding blaVIM-1 was identical to that reported previously in Italy [6], which suggests the possibility of a conserved blaVIM-1 integron structure in nonclonally related P. aeruginosa isolates, as has also been suggested recently by Riccio et al. [9].