Emergence of Escherichia coli sequence type 131 isolates producing KPC-2 carbapenemase in China

Abstract

Twenty-two KPC-2-producing Escherichia coli isolates were obtained from three hospitals in Hangzhou, China, from 2007 to 2011. One isolate, with OmpC porin deficiency, exhibited high-level carbapenem resistance. Pulsed-field gel electrophoresis showed that few isolates were indistinguishable or closely related. Multilocus sequence typing indicated that sequence type 131 (ST131) was the predominant type (9 isolates, 40.9%), followed by ST648 (5 isolates), ST405 (2 isolates), ST38 (2 isolates), and 4 single STs, ST69, ST2003, ST2179, and ST744. Phylogenetic analysis indicated that 9 group B2 isolates belonged to ST131, and 5 of 11 group D isolates belonged to ST648. Only one group B1 isolate and one group A isolate were identified. A representative plasmid (pE1) was partially sequenced, and a 7,788-bp DNA fragment encoding Tn3 transposase, Tn3 resolvase, ISKpn8 transposase, KPC-2, and ISKpn6-like transposase was obtained. The blaKPC-2-surrounding sequence was amplified by a series of primers. The PCR results showed that 13 isolates were consistent with the genetic environment in pE1. It is the first report of rapid emergence of KPC-2-producing E. coli ST131 in China. The blaKPC-2 gene of most isolates was located on a similar genetic structure.

FIG 1

Plasmid profiles of E. coli isolates and E. coli transconjugants. E1 to E22, 22 E. coli isolates; TE1 to TE22, transconjugants of E. coli isolates; E. coli V517 was used as molecular size reference.

FIG 2

SDS-PAGE analysis of outer membrane proteins extracted from E. coli ATCC 25922, E1, E6, E13, and E21.

FIG 3

(A) PFGE patterns of chromosomal DNA restriction fragments from 22 E. coli isolates. Salmonella serotype Braenderup H9812 restricted with XbaI was used as molecular size standard. (B) Dendrogram of PFGE patterns. ZJUH, 2nd Affiliated Hospital of Zhejiang University; HZTCMH, Hangzhou Traditional Chinese Medicine Hospital; ZJPPH, Zhejiang Provincial People's Hospital.

FIG 4

Schematic representation of the genetic structure surrounding the bla_KPC-2 gene on plasmid pE1 from E. coli E1. Genes and their corresponding transcription orientations are indicated by arrows with various types of shading. Triangles represent the inverted repeats of the respective mobile elements, and target site duplications are presented as nucleotide letters. Short arrowheads show the primers (listed in Table 3) used for PCR amplification of the bla_KPC-2-surrounding sequences from other KPC-2-producing E. coli strains.