Complete sequencing of the FII plasmid pHK01, encoding CTX-M-14, and molecular analysis of its variants among Escherichia coli from Hong Kong

J Antimicrob Chemother. 2011 Apr;66(4):752-6. doi: 10.1093/jac/dkr010. Epub 2011 Feb 7.


Objectives: We characterized plasmids encoding CTX-M-14 β-lactamase originating from Escherichia coli isolates recovered from patients with uncomplicated cystitis or individuals with faecal colonization in Hong Kong from 2002 to 2004.

Methods: Plasmids carrying CTX-M-14 were studied by conjugation, replicon typing, S1 nuclease-PFGE and plasmid PCR-restriction fragment length polymorphism (RFLP). The complete sequence of pHK01, a 70 kb plasmid encoding CTX-M-14 from an E. coli strain, was determined and the results compared with reference plasmids and aligned with GenBank data.

Results: The blaCTX-M-14 plasmids could be transferred in 23 of 44 E. coli strains tested. Among the 23 transconjugants, the replicon types of the CTX-M-14-encoding plasmid were FII (n=13), I1-Iγ (n=4), F1B (n=2), FII and I1-Iγ (n=1), K (80 kb, n=1) and undetermined (n=2). Plasmid pHK01 (FII replicon) shares a high degree of homology with R100 except mainly for a 11 kb variable region containing blaCTX-M-14 (with an upstream ISEcp1 and a downstream truncated IS903), an iron transport system, an outer membrane protein (malB, maltoporin) and a putative toxin-antitoxin plasmid stability system (yacABC). It was highly related to blaCTX-M-14 (pKF3-70) and blaCTX-M-24 (pEG356) plasmids reported from mainland China in 2006 and Vietnam in 2007, respectively. Subtyping by a plasmid PCR-RFLP scheme showed that 10 of the 13 FII plasmids originating from isolates collected by multiple laboratories exhibited either identical or highly similar profiles.

Conclusions: This study showed that narrow host-range FII plasmids play important roles in the dissemination of CTX-M-14. FII plasmids closely related to pHK01 have disseminated widely in the Hong Kong community.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Child
  • Child, Preschool
  • Conjugation, Genetic
  • Cystitis / microbiology
  • DNA, Bacterial / chemistry*
  • DNA, Bacterial / genetics*
  • Escherichia coli / enzymology
  • Escherichia coli / genetics*
  • Escherichia coli / isolation & purification
  • Escherichia coli Infections / microbiology
  • Female
  • Genotype
  • Hong Kong
  • Humans
  • Molecular Sequence Data
  • Plasmids*
  • Polymerase Chain Reaction
  • Polymorphism, Restriction Fragment Length
  • Sequence Analysis, DNA
  • beta-Lactamases / genetics


  • DNA, Bacterial
  • beta-lactamase CTX-M-14
  • beta-Lactamases

Associated data

  • GENBANK/HM355591