Molecular and phenotypic characterization of Escherichia coli and Klebsiella pneumoniae producing extended-spectrum β-lactamases with focus on CTX-M in a low-endemic area in Sweden

APMIS. 2011 Apr;119(4-5):287-95. doi: 10.1111/j.1600-0463.2011.02730.x. Epub 2011 Mar 22.


During the last decade increasing prevalence of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae has been detected worldwide, mainly due to dissemination of Escherichia coli and Klebsiella pneumoniae producing CTX-M-type ESBLs. CTX-M-15 is the most widespread CTX-M type, and the predominant type in various countries. Dissemination of ESBL-producing organisms is caused not only by horizontal transfer of plasmids, but also by clonal spread of ESBL-producing strains. In this study, the molecular epidemiology of class A ESBL (ESBL(A))-producing E. coli and K. pneumoniae isolated in Örebro County, Sweden, was investigated. Out of 200 ESBL(A) -producing E. coli and K. pneumoniae isolates, collected over a 10-year period, 87% were producing CTX-M, belonging to subgroup CTX-M-1 (64%), CTX-M-9 (34%), or CTX-M-2 (2%). The remaining isolates were producing variants of SHV and TEM. Sequencing of the bla(CTX-M) genes revealed 10 different CTX-M types, with a dominance of CTX-M-15 (E. coli 54%, K. pneumoniae 50%) followed by CTX-M-14 (E. coli 28%, K. pneumoniae 27%). Phenotypic characterization of the CTX-M-producing isolates was performed using the PhenePlate system. Although a few minor clusters of CTX-M-15 and CTX-M-14 producers were identified, the majority of the isolates did not appear to be clonally related.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Base Sequence
  • DNA Primers / genetics
  • DNA, Bacterial / genetics
  • Endemic Diseases
  • Escherichia coli / classification
  • Escherichia coli / enzymology*
  • Escherichia coli / genetics*
  • Escherichia coli / isolation & purification
  • Escherichia coli Infections / epidemiology
  • Escherichia coli Infections / microbiology*
  • Genes, Bacterial
  • Humans
  • Klebsiella Infections / epidemiology
  • Klebsiella Infections / microbiology*
  • Klebsiella pneumoniae / classification
  • Klebsiella pneumoniae / enzymology*
  • Klebsiella pneumoniae / genetics*
  • Klebsiella pneumoniae / isolation & purification
  • Molecular Epidemiology
  • Phenotype
  • Phylogeny
  • Sweden / epidemiology
  • beta-Lactamases / biosynthesis*
  • beta-Lactamases / classification
  • beta-Lactamases / genetics*


  • DNA Primers
  • DNA, Bacterial
  • beta-Lactamases