Molecular typing and genetic environment of the blaKPC gene in Chilean isolates of Klebsiella pneumoniae

The aim of this work was to determine the genetic environment and transferability of blaKPC as well as the pulsotypes of KPC-producing Klebsiella pneumoniae strains isolated from clinical samples in Chilean hospitals. Seventeen strains, principally isolated in Santiago (the capital of Chile) during the years 2012 and 2013, were included. The genetic environment of blaKPC was elucidated by PCR mapping and sequencing. Molecular typing was performed by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Curing and conjugation experiments were performed with six strains of different sequence types (STs) and pulsotypes. Thirteen pulsotypes and six STs, mainly belonging to clonal complex 258, were found. In addition, seven strains belonged to a new ST assigned ST1161. The blaKPC sequence indicated that 16 strains had the KPC-2 variant; in only one strain (UC331) an amino acid change (R6P) was detected, corresponding to a new KPC variant designated KPC-24. Molecular characterisation of the blaKPC genetic environment revealed two distinct platforms, namely variant 1a and the Tn4401a isoform, with the first being the most common (11/17 strains). Mating experiments failed to produce transconjugants; however, loss of blaKPC was achieved by plasmid curing in all assayed strains. In conclusion, in Chilean strains of K. pneumoniae, blaKPC is primarily found associated with the variant 1a and is located in non-transferable plasmids. In addition, this study highlights the description of the new ST1161 and the new KPC-24 variant.