Molecular epidemiology of metallo-beta-lactamase-producing Pseudomonas aeruginosa isolates from Norway and Sweden shows import of international clones and local clonal expansion.

Abstract

Scandinavia is considered a region with a low prevalence of antimicrobial resistance. However, the number of multidrug-resistant (MDR) Gram-negative bacteria is increasing, including metallo-beta-lactamase (MBL)-producing Pseudomonas aeruginosa. In this study MBL-producing P. aeruginosa isolates identified in Norway (n = 4) and Sweden (n = 9) from 1999 to 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 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 integron In59.2 or In59 variants. The two CC235 isolates (ST235/ST230; serotype O11; bla(VIM-4)) were imported from Greece and Cyprus, 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 was part of a new CC (CC233) that included 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 successful international clones and local clonal expansion contribute to the emergence of MBL-producing P. aeruginosa in Scandinavia.