Extended-spectrum {beta}-lactamases and AmpC {beta}-lactamases in ceftiofur-resistant Salmonella enterica isolates from food and livestock obtained in Germany during 2003-07.
OBJECTIVE
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.
Rodríguez
Irene
I
Departamento de Biología Funcional, Area de Microbiología, Universidad de Oviedo, 33006 Oviedo, Spain.
Barownick
Wolfgang
W
Helmuth
Reiner
R
Mendoza
M Carmen
MC
Rodicio
M Rosario
MR
Schroeter
Andreas
A
Guerra
Beatriz
B
D000818:Animals; D000829:Animals, Domestic / Q000382:microbiology; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002511:Cephalosporins / Q000494:pharmacology*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field; D005516:Food Microbiology; D005858:Germany; D006801:Humans; D007526:Isoelectric Point; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D010957:Plasmids / Q000032:analysis; D012481:Salmonella Infections, Animal / Q000382:microbiology*; D019779:Salmonella enterica / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D017422:Sequence Analysis, DNA; D018440:beta-Lactam Resistance; D001618:beta-Lactamases / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics
D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D004269:DNA, Bacterial; C053503:ceftiofur; D001618:beta-Lactamases