Carbapenem-resistant KPC-2-producing Escherichia coli in a Tel Aviv Medical Center, 2005 to 2008

Abstract

All of the carbapenem-resistant Escherichia coli (CREC) isolates identified in our hospital from 2005 to 2008 (n = 10) were studied. CREC isolates were multidrug resistant, all carried bla(KPC-2), and six of them were also extended-spectrum beta-lactamase producers. Pulsed-field gel electrophoresis indicated six genetic clones; within the same clone, similar transferable bla(KPC-2)-containing plasmids were found whereas plasmids differed between clones. Tn4401 elements were identified in all of these plasmids.

FIG. 1.

PFGE of clinical CREC isolates. Shown are DNA restriction patterns and a dendrogram showing the level of similarity between SpeI-restricted patterns of CREC isolates. Isolates with asterisks were described previously (21). The scale indicates the degree of genetic relatedness between the strains. Isolates were placed into six different clusters based on GelCompar Dice algorithm coefficients, which range from 0 to 100%, as illustrated by the scale to the left of each dendrogram. The year of isolation of each isolate is shown at the right.

FIG. 2.

PFGE after S1 restriction of donor clinical strains and transformants (A) and Southern blotting using a bla_KPC-2 probe (B). Plasmid profiles of six CREC isolates representing genetic clusters I to V and their transformants as determined by S1 nuclease treatment, followed by PFGE (A) and Southern blot analysis using bla_KPC-2 probe (B). Lane M, Lambda Ladder PFG Marker (New England Biolabs, Boston, MA); lanes 1 to 12, E. coli clinical isolates (D) and their respective transformants (T).

FIG. 3.

Restriction analysis of bla_KPC-2-harboring plasmids (A) and Southern blotting using a bla_KPC-2 probe (B). Restriction analysis of bla_KPC-2-containing plasmids derived from six CREC isolates after EcoRV (A) or SmaI (B) digestion, followed by Southern blotting using a bla_KPC-2 probe. The two isolates belonging to cluster I (isolates 360 and 386) display the same restriction pattern; therefore, isolate 386 was chosen to depict the restriction pattern of both isolates. SmaI endonuclease cleaves bla_KPC-2 at position 790 and the IstB and ISKpn6 open reading frames at positions 203 and 676, respectively, creating fragments of ∼1 and ∼1.5 kb. Lanes M, 1-kb DNA ladder (New England Biolabs, Boston, MA).