Identification of bla LAP-2 and qnrS1 genes in the internationally successful Klebsiella pneumoniae ST147 clone

Abstract

We investigated the presence of β-lactamase genes (bla) in 26 strains of Enterobacteriaceae already found positive for the qnrS1 gene, a plasmid-mediated quinolone resistance determinant. Three strains of K. pneumoniae, isolated in the period 2008-2009 at the University Hospital in Verona, were positive for LAP-2, a narrow-spectrum β-lactamase. These strains, namely VRB586, VRE185 and VRE196, were cultured from urine, bile and peritoneal drainage, respectively, of different patients from different units. The bla(LAP-2) and qnrS1 resistance determinant genes were separated by ISEcl2 and were located on a 97 kb conjugable and untypable plasmid, which could be transferred to a recipient strain, E. coli J53. The fluoroquinolone and ceftazidime MICs increased 1-2-fold in the transconjugant cells. The three K. pneumoniae strains were found to be clonal by PFGE and were identified as belonging to ST147, an internationally successful clone, by MLST. The plasmid sequence, including ISEcl2 and qnrS1 genes, of K. pneumoniae ST147 was found to be highly similar to previously detected qnrS1-harbouring plasmids, suggesting the plasmid has a stable genetic structure and that these resistance determinants have a common source. To the best of our knowledge, this is the first report of the internationally successful K. pneumoniae ST147 strain carrying bla(LAP-2) and qnrS1 genes and is the first case of LAP β-lactamase in Italy.