Emergence of clonally related Klebsiella pneumoniae isolates of sequence type 258 producing plasmid-mediated KPC carbapenemase in Norway and Sweden

Background: The class A carbapenemase KPC has disseminated rapidly worldwide, challenging the treatment of Gram-negative infections. This report describes the first KPC-producing Klebslella pneumoniae isolates identified in Norway (n=6) and the second isolate from Sweden. Methods: Antimicrobial susceptibility profiles were determined using Etest. PCR and sequencing were used to determine the bla KPC variant, the surrounding genetic structure and the presence of AmpC and extended-spectrum β-lactamase genes. PFGE and multilocus sequence typing (MLST) were used for epidemiological comparisons. Localization of bla KPC was investigated by S1 nuclease digestion, followed by PFGE and Southern blot hybridization. Results: All isolates expressed a multidrug-resistant phenotype with some variability in the carbapenem susceptibility profile. The Norwegian isolates carried bla KPC-2 , while the Swedish isolate carried bla KPC-3 . All isolates carried TEM-1, but were negative for bla CTX-M and bla Ampc genes. SHV-11 and SHV-12 were detected in the Norwegian isolates, while the Swedish isolate carried only SHV-11. Isolates from four patients were associated with import from Greece (n=3) and Israel. The other isolates were probably associated with local transmissions. PFGE and MLST showed that the isolates were clonally related, with three isolates displaying ST258, a single locus variant of ST11 previously associated with the clonal spread of CTX-M-15-producing K. pneumoniae in Hungary. In all isolates, bla KPC was located on plasmids as part of isoform a of Tn4401. Conclusions: The emergence of KPC-producing isolates of K. pneumoniae in Norway and Sweden is associated with multiple import events and probable local transmission of a successful multiresistant ST258 clone, closely related to the CTX-M-15-producing ST11 clone previously described in Hungary.