[Molecular characterization of Pseudomonas aeruginosa isolates in Cantabria, Spain, producing VIM-2 metallo-beta-lactamase].

Introduction: Pseudomonas aeruginosa strains producing metallo-beta-lactamases (MbetaL) are uncommon in Spain. This study describes the characterization of 9 new clonally related multiresistant P. aeruginosa isolates possessing the bla(VIM-2) gene in Cantabria (Northern Spain).

Methods: P. aeruginosa clinical strains (1 per patient) were isolated in the Microbiology Service of Marqués de Valdecilla University Hospital between January 2004 and December 2006. Identification and preliminary susceptibility studies were performed with the MicroScan WalkAway system (Dade Behring, Sacramento, CA) and results were verified by a microdilution reference method.

Results: MICs of imipenem and meropenem for the 9 isolates ranged from 32 to 128 and 16 to 64 microg/mL, respectively. Nine isolates had a single Rep-PCR pattern and were intermediate or resistant to ceftazidime, cefepime, gentamicin, tobramycin, amikacin and ciprofloxacin. Eight of the 9 isolates were susceptible to aztreonam. Hydrolysis activity of imipenem in MbetaL-positive isolates ranged from 162+/-18 to 235+/-28 pmol/min/microg protein and was abolished in the presence of 5 mM EDTA. All isolates possessed an integron with genes aac(6')32, bla(VIM-2) and a putative transposase-encoding gene, flanked by the conserved 5'CS and 3'CS regions.

Conclusion: In the clinical isolates studied, the presence of MbetaL VIM-2 sufficed to explain their resistance to carbapenems.