AAC Accepts, published online ahead of print on 2 November 2009

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Antimicrob. Agents Chemother. doi:10.1128/AAC.00824-09
Copyright (c) 2009, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Molecular Epidemiology of Metallo--Lactamase Producing Pseudomonas aeruginosa From Norway and Sweden show Import of International Clones and Local Clonal Expansion

rjan Samuelsen^*, Mark A. Toleman, Arnfinn Sundsfjord, Johan Rydberg, Truls M. Leegaard, Mats Walder, Astrid Lia, Trond E. Ranheim, Yashas Rajendra, Nils O. Hermansen, Timothy R. Walsh, and Christian G. Giske

Reference Centre for Detection of Antimicrobial Resistance, Department of Microbiology and Infection Control, University Hospital of North Norway, Tromsø, Norway; Department of Microbiology and Virology, University of Tromsø, Tromsø, Norway; Karolinska-Institutet-MTC, Karolinska University Hospital, Solna, Department of Clinical Microbiology, Stockholm, Sweden; Department of Medical Microbiology, School of Medicine, Cardiff University, Cardiff, UK; Department of Clinical Microbiology, University Hospital of Lund, Sweden; Institute of Medical Microbiology, Rikshospitalet University Hospital, Oslo, Norway; Medical Microbiology, Department of Laboratory Medicine, Malmö University Hospital, Lund University, Malmö, Sweden; Department of Microbiology, Vestfold Hospital, Tønsberg, Norway; Department of Microbiology, Centre for Laboratory Medicine, Akershus University Hospital, Lørenskog, Norway; Department of Microbiology, Ullevaal University Hospital, Oslo, Norway

^* To whom correspondence should be addressed. Email: orjan.samuelsen{at}unn.no.

Scandinavia is considered a region with low prevalence of antimicrobial resistance. However, the number of multi-drug resistant (MDR) Gram-negative bacteria is increasing, including metallo--lactamase (MBL)-producing Pseudomonas aeruginosa. In this study MBL-producing P. aeruginosa identified in Norway (n=4) and Sweden (n=9) 1999-2007 were characterized. Two international clonal complexes (CC), CC111 (n=8) and CC235 (n=2) previously associated with MBL-producing isolates were dominant. CC111 isolates (ST111/229, serotype O12, bla_VIM-2) included clonally related isolates identified in the Skåne County, Sweden (n=6) and two isolates associated with importation from Greece and Denmark. In all CC111 isolates bla_VIM-2 was located in In59.2 or in In59-variants. The two CC235 isolates (ST235/ST230, serotype O11, bla_VIM-4), were imported from Greece and Cyprus and were possibly clonally related and carried bla_VIM-4 in two different integron structures. Three isolates imported from Ghana (ST233, serotype O6, bla_VIM-2), Tunisia (ST654, serotype O11, bla_VIM-2) and Thailand (ST260, serotype O6, bla_IMP-14) were clonally unrelated. ST233 were part of a new CC (CC233) which include other MBL-producing isolates while ST654 could also be part of a new CC associated with MBL-producers. In the isolates imported from Ghana and Tunisia bla_VIM-2 was part of unusual integron structures lacking the 3'conserved segment and associated with transposons. The bla_VIM gene was found to be located on the chromosome in all isolates. Known risk factors for acquisition of MBL were reported for all patients except one. The findings suggest that both import of international successful clones and local clonal expansion contribute to the emergence of MBL-producing P. aeruginosa in Scandinavia.