CTX-M-15 extended-spectrum (beta)-lactamase from Nigerian Klebsiella pneumoniae

J Antimicrob Chemother. 2006 Jan;57(1):24-30. doi: 10.1093/jac/dki429. Epub 2005 Nov 30.


Objectives: In this study, extended-spectrum beta-lactamases (ESBLs) were characterized from 30 selected multidrug-resistant Klebsiella pneumoniae strains isolated from patients with community-acquired urinary tract infections from Southwest Nigeria.

Methods: The beta-lactamases were phenotypically characterized using isoelectric focusing, genotypically characterized using PCR assays and hybridization of the PCR products. Two of the bla(CTX-M) genes were completely sequenced. The location of the CTX-M-type genes was determined using transformation, DNA-DNA hybridization, PCR assays and hybridization of the PCR products from the Escherichia coli transformants.

Results: All 30 isolates produced at least one beta-lactamase. Seventeen of the isolates were resistant to cefotaxime, and had > or =100-fold reduction in susceptibility with cefotaxime plus clavulanic acid (4 mg/L), indicating the presence of an ESBL. The 17 isolates were shown to have bla(CTX-M) genes that were associated with large plasmids (> or =58 kb), which also carried a tetracycline resistance gene, tet(A), and various aminoglycoside resistance genes. Two CTX-M-type genes were sequenced and had amino acid sequences indistinguishable from previously sequenced CTX-M-15 beta-lactamases. The ISEcp1 element was located upstream of bla(CTX-M-15) in the same position as previously described. In addition, 23 of the isolates produced TEM beta-lactamases, 27 produced SHV beta-lactamases and four produced AmpC beta-lactamases.

Conclusions: Thirty K. pneumoniae produced multiple beta-lactamases, with 57% producing CTX-M enzymes. This is the first characterization of CTX-M-15-positive K. pneumoniae in Western Africa.

MeSH terms

  • Anti-Bacterial Agents / pharmacology
  • Base Sequence
  • Community-Acquired Infections / epidemiology
  • Community-Acquired Infections / microbiology*
  • DNA, Bacterial / genetics
  • Drug Resistance, Multiple, Bacterial / genetics
  • Escherichia coli / genetics
  • Female
  • Genes, Bacterial*
  • Humans
  • In Situ Hybridization
  • Isoelectric Focusing
  • Klebsiella Infections / epidemiology
  • Klebsiella Infections / microbiology*
  • Klebsiella pneumoniae / drug effects
  • Klebsiella pneumoniae / enzymology*
  • Klebsiella pneumoniae / isolation & purification
  • Male
  • Microbial Sensitivity Tests
  • Molecular Sequence Data
  • Nigeria / epidemiology
  • Plasmids
  • Urinary Tract Infections / epidemiology
  • Urinary Tract Infections / microbiology*
  • beta-Lactamases / genetics*


  • Anti-Bacterial Agents
  • DNA, Bacterial
  • beta-lactamase CTX-M-15
  • beta-Lactamases

Associated data

  • GENBANK/AY995205
  • GENBANK/AY995206