title: Presence of β-lactamases in extended-spectrum-cephalosporin-resistant Salmonella enterica of 30 different serovars in Germany 2005-11.
abstract: OBJECTIVE
  Between 20 000 and 35 000 cases of salmonellosis are detected annually in Germany, but only a few Salmonella are resistant to third-generation cephalosporins. The German National Reference Centre for Salmonella and other Enterics obtained 150 Salmonella enterica isolates from human infections between 2005 and 2011. In the present study we identified the β-lactamase genes causing resistance to third-generation cephalosporins in these isolates.
  
  
  METHODS
  For all isolates serotyping and antimicrobial susceptibility testing were performed. The presence of β-lactamase genes was detected by PCR amplification and sequencing. Isolates with identical serovar and β-lactamase genes were typed by XbaI macrorestriction followed by PFGE. Broth mate conjugation assays and plasmid analysis using S1 nuclease restriction of genomic DNA and subsequent PFGE as well as PCR-based replicon typing were performed for selected isolates.
  
  
  RESULTS
  The 150 isolates were assigned to 30 different serovars, with S. enterica serovar Typhimurium (n = 73; 48.7%) as the most prevalent. Two different AmpC β-lactamase genes (blaCMY-2, n = 8; blaACC-1, n = 6) and various extended-spectrum β-lactamase (ESBL) genes were identified. The majority harboured the blaCTX-M-1 gene (n = 91; 60.7%) followed by blaCTX-M-14 (n = 12; 8.0%) and blaSHV-12 (n = 11; 7.3%). Typing of strains and subsequent comparison with selected Salmonella isolates from livestock revealed the presence of several clones in both humans and livestock.
  
  
  CONCLUSIONS
  The wide spread of ESBL and AmpC genes in Salmonella of various serovars is most probably due to transfer of conjugative plasmids. Furthermore, our data indicate the clonal spread of distinct cephalosporin-resistant Salmonella strains from livestock to humans.
authors.affiliation: Division of Nosocomial Infections, Robert Koch Institute, Wernigerode, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Eller
authors.forename: Sandra
authors.initials: S
authors.lastname: Simon
authors.forename: Tatjana
authors.initials: T
authors.lastname: Miller
authors.forename: Julia-Stefanie
authors.initials: JS
authors.lastname: Frick
authors.forename: Rita
authors.initials: R
authors.lastname: Prager
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Rabsch
authors.forename: Beatriz
authors.initials: B
authors.lastname: Guerra
authors.forename: Guido
authors.initials: G
authors.lastname: Werner
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Pfeifer
mesh_terms: D000818:Animals; D002511:Cephalosporins / Q000494:pharmacology*; D003227:Conjugation, Genetic; D004269:DNA, Bacterial / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field; D022761:Gene Transfer, Horizontal; D005858:Germany / Q000453:epidemiology; D006801:Humans; D008826:Microbial Sensitivity Tests; D017720:Molecular Epidemiology; D058889:Molecular Typing; D010957:Plasmids; D016133:Polymerase Chain Reaction; D012480:Salmonella Infections / Q000453:epidemiology / Q000382:microbiology* / Q000635:transmission; D019779:Salmonella enterica / Q000145:classification* / Q000187:drug effects / Q000201:enzymology* / Q000302:isolation & purification; D017422:Sequence Analysis, DNA; D012703:Serotyping; D018440:beta-Lactam Resistance; D001618:beta-Lactamases / Q000235:genetics* / Q000378:metabolism
chemical_list: D002511:Cephalosporins; D004269:DNA, Bacterial; D001618:beta-Lactamases
keywords: AmpC; CMY-2; CTX-M-15; ESBLs; antimicrobial resistance