Long-term evolution of a nosocomial outbreak of Pseudomonas aeruginosa producing VIM-2 metallo-enzyme.

From April 1996 to July 2004, an outbreak of metallo-beta-lactamase-positive (MBL) Pseudomonas aeruginosa occurred in the haematology ward at Nantes University Hospital in France. Fifty-nine patients were carriers of VIM-2-positive strains of whom 14 were infected (mostly urinary tract infections and pneumonia). Pulsed-field gel electrophoresis identified related isolates demonstrating resistance to all beta-lactams, aminoglycosides, fluoroquinolones, fosfomycin, rifampicin but not colistin. The bla(VIM-2) gene responsible for VIM-2 MBL was not plasmid-encoded but part of a novel type of class 1 integron. VIM-2-positive strains were mostly from urine samples and clinical data suggest that in the absence of therapeutic guidelines, piperacillin-tazobactam or aztreonam may be a reliable choice for treating infections with MBL-producing strains.