title: Limited similarity between plasmids encoding CTX-M-1 β-lactamase in Escherichia coli from humans, pigs, cattle, organic poultry layers and horses in Denmark.
abstract: CTX-M-1 is a common extended-spectrum β-lactamase (ESBL) in Escherichia coli from animals and is often detected among human clinical isolates. The objective of this study was to investigate the epidemiological relationship between CTX-M-1-producing E. coli isolated from patients and animals in Denmark between 2006 and 2010. In total, 65 CTX-M-1-producing isolates from patients (n=22), pigs (n=21), cattle (n=4), organic poultry layers (n=3) and horses (n=15) were typed by pulsed-field gel electrophoresis (PFGE). Plasmids harbouring blaCTX-M-1were characterised by S1 PFGE, PCR-based replicon typing, plasmid multilocus sequence typing, restriction fragment length polymorphism, and sequencing. Human and animal strains were unrelated based on PFGE. IncI1 was more common in human isolates (13/22) than in animal isolates (7/43), whereas the opposite trend was observed for IncN (5/22 human isolates and 24/43 animal isolates). Full characterisation of the plasmids harbouring blaCTX-M-1revealed host-specific patterns in the distribution of plasmid types, with specific IncI1, IncN and IncH1 plasmid subtypes being predominant in humans, livestock and horses, respectively. Three indistinguishable human, bovine and porcine IncI1/ST49 plasmids had high nucleotide sequence homology and differed by the presence of IS66 elements in the bovine plasmid and the absence of one gene within the microcin-encoding operon in the human plasmid. In conclusion, this work suggests a minor contribution by animals to the occurrence of CTX-M-1 in human E. coli infections in Denmark during the study period.
authors.affiliation: Microbiology and Infection Control, Statens Serum Institut, 5 Artillerivej, DK-2300 Copenhagen S, Denmark. Electronic address: lottejakobsen@gmail.com.
authors.forename: Lotte
authors.initials: L
authors.lastname: Jakobsen
authors.affiliation: Department of Veterinary Disease Biology, University of Copenhagen, Stigbøjlen 4, DK-1870 Frederiksberg C, Denmark.
authors.forename: Valeria
authors.initials: V
authors.lastname: Bortolaia
authors.affiliation: National Food Institute, Technical University of Denmark, 204 Kemitorvet, DK-2800 Kgs., Lyngby, Denmark.
authors.forename: Eliza
authors.initials: E
authors.lastname: Bielak
authors.affiliation: Department of Veterinary Disease Biology, University of Copenhagen, Stigbøjlen 4, DK-1870 Frederiksberg C, Denmark.
authors.forename: Arshnee
authors.initials: A
authors.lastname: Moodley
authors.affiliation: Microbiology and Infection Control, Statens Serum Institut, 5 Artillerivej, DK-2300 Copenhagen S, Denmark.
authors.forename: Stefan S
authors.initials: SS
authors.lastname: Olsen
authors.affiliation: Department of Clinical Microbiology, Copenhagen University Hospital Herlev, 75 Herlev Ringvej, DK-2730 Herlev, Denmark.
authors.forename: Dennis S
authors.initials: DS
authors.lastname: Hansen
authors.affiliation: Department of Clinical Microbiology, Copenhagen University Hospital Rigshospitalet, 9 Blegdamsvej, DK-2100 Copenhagen, Denmark.
authors.forename: Niels
authors.initials: N
authors.lastname: Frimodt-Møller
authors.affiliation: Department of Veterinary Disease Biology, University of Copenhagen, Stigbøjlen 4, DK-1870 Frederiksberg C, Denmark.
authors.forename: Luca
authors.initials: L
authors.lastname: Guardabassi
authors.affiliation: National Food Institute, Technical University of Denmark, 204 Kemitorvet, DK-2800 Kgs., Lyngby, Denmark.
authors.forename: Henrik
authors.initials: H
authors.lastname: Hasman
keywords: CTX-M-1; Escherichia coli; Humans and animals; IncI1; IncN; Plasmid sequencing