The CTX-M-15-producing Escherichia coli diffusing clone belongs to a highly virulent B2 phylogenetic subgroup

J Antimicrob Chemother. 2008 May;61(5):1024-8. doi: 10.1093/jac/dkn084. Epub 2008 Mar 11.


Objectives: A clone of CTX-M-15-producing Escherichia coli has recently been reported to be spreading through Europe and Africa. The aim of this work was to thoroughly characterize this clone.

Materials and methods: Representative isolates of this clone were subjected to multilocus sequence typing, O typing, virulence gene detection, adhesion assay on human cells, biofilm production assay and mouse lethality assay.

Results: The clone: (i) belongs to a unique B2 phylogenetic subgroup encompassing the pyelonephritogenic diffusely adhering EC7372 strain; (ii) exhibits a specific O25b molecular subtype; (iii) is identical to the E. coli clone O25:H4-ST131 producing CTX-M-15; (iv) produces biofilm; and (v) is highly virulent in mice despite lacking classical extraintestinal pathogenicity islands (except for high pathogenicity island) and the afa/dra gene.

Conclusions: The CTX-M-15-producing E. coli diffusing clone is associated with a high level of antibiotic resistance and with high virulence, showing that, under certain selective pressures, the previously observed trade-off between resistance and virulence may not apply.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line
  • Escherichia coli / classification
  • Escherichia coli / drug effects
  • Escherichia coli / genetics*
  • Escherichia coli / metabolism*
  • Escherichia coli / pathogenicity
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / metabolism
  • Humans
  • Phylogeny
  • Virulence
  • beta-Lactam Resistance / genetics
  • beta-Lactamases / genetics
  • beta-Lactamases / metabolism*


  • Escherichia coli Proteins
  • beta-lactamase CTX-M-15
  • beta-Lactamases