Extended-spectrum {beta}-lactamases and AmpC {beta}-lactamases in ceftiofur-resistant Salmonella enterica isolates from food and livestock obtained in Germany during 2003-07

J Antimicrob Chemother. 2009 Aug;64(2):301-9. doi: 10.1093/jac/dkp195. Epub 2009 May 27.


Objectives: Detection and characterization of extended-spectrum beta-lactamases (ESBLs) and AmpC-encoding genes was conducted in German Salmonella isolated from different sources from 2003 to 2007.

Methods: Non-duplicate German isolates from the National Salmonella Reference Laboratory Collection (2003-07) with ceftiofur MICs of > or =4 mg/L were tested for beta-lactam/beta-lactamase inhibitor susceptibility, presence of ESBLs or AmpC-encoding genes, class 1 and 2 integrons, other resistance genes, and IS26 and ISEcp1 sequences by PCR/sequencing. The isoelectric point of the beta-lactamase was determined. Strains were analysed by PFGE and plasmid profiling. The bla genes were mapped by Southern-blot hybridization. Plasmids were characterized by rep-PCR typing.

Results: Sixteen isolates (10 Salmonella Typhimurium, 2 Salmonella Anatum, 2 Salmonella Paratyphi B dT + , 1 Salmonella Infantis and 1 Salmonella London) carried bla(CTX-M) (15 bla(CTX-M-1) and one bla(CTX-M-15)) genes located on self-transferable IncB/O, IncI1 and/or IncN plasmids. Seven of the Salmonella Typhimurium isolates carried the SGI1-M variant. Six isolates (five Salmonella Agona and one Salmonella Kentucky) carried the bla(CMY-2) gene on IncI1 conjugative plasmids. bla(TEM-20) genes were detected in two Salmonella Paratyphi B dT+ isolates, and bla(TEM-52) in one Salmonella Paratyphi B dT+ and one Salmonella Virchow, located on IncI1 plasmids. All Salmonella Paratyphi isolates harboured a 2300 bp/dfrA1-sat2-aadA1 class 2 integron.

Conclusions: Among the 22 679 German Salmonella isolates investigated, the ESBL and AmpC beta-lactamase prevalence was still low; however, it is slowly increasing. Various beta-lactamase genes are linked to a variety of genetic elements capable of horizontal DNA transfer. Consequently, their dissemination is likely and demands adequate risk management strategies.

MeSH terms

  • Animals
  • Animals, Domestic / microbiology
  • Anti-Bacterial Agents / pharmacology*
  • Cephalosporins / pharmacology*
  • DNA, Bacterial / chemistry
  • DNA, Bacterial / genetics
  • Electrophoresis, Gel, Pulsed-Field
  • Food Microbiology*
  • Germany
  • Humans
  • Isoelectric Point
  • Microbial Sensitivity Tests
  • Molecular Sequence Data
  • Plasmids / analysis
  • Salmonella Infections, Animal / microbiology*
  • Salmonella enterica / drug effects*
  • Salmonella enterica / genetics
  • Salmonella enterica / isolation & purification
  • Sequence Analysis, DNA
  • beta-Lactam Resistance*
  • beta-Lactamases / biosynthesis*
  • beta-Lactamases / chemistry
  • beta-Lactamases / genetics


  • Anti-Bacterial Agents
  • Cephalosporins
  • DNA, Bacterial
  • ceftiofur
  • beta-Lactamases

Associated data

  • GENBANK/FM865623
  • GENBANK/FM865624
  • GENBANK/FM865625