High diversity of plasmids harbouring blaCMY-2 among clinical Escherichia coli isolates from humans and companion animals in the upper Midwestern USA.
OBJECTIVE
To determine the population structure and genetic relatedness of plasmids encoding CMY-2 β-lactamase in clinical Escherichia coli from humans and companion animals within a defined geographical area.


METHODS
In total, 42 human and 73 companion animal isolates displaying an AmpC phenotype were isolated at a regional diagnostic reference laboratory in the upper Midwestern USA during 2009-11. Following PCR screening for transferable AmpC genes and plasmid transformation, blaCMY-2-positive plasmids were characterized by S1 nuclease PFGE, PCR-based replicon typing, antimicrobial susceptibility testing of transformants, conjugation experiments, plasmid multilocus sequence typing and restriction fragment length polymorphism.


RESULTS
blaCMY-2 occurred in 6 (14%), 56 (86%) and 6 (75%) isolates from humans, dogs and cats, respectively. Usually plasmids carrying blaCMY-2 were conjugative (78%) and did not contain additional resistance genes (82%). The replicon types were IncI1 (52%), IncA/C (13%), IncFII (10%), IncI2 (5%), IncL/M (3%), IncB/O (2%) or non-typeable (15%). Related IncI1/ST12 plasmids were detected in one human and five canine isolates, while the remaining plasmids did not show similarity across host species. A novel epidemiological linkage of blaCMY-2 with IncL/M plasmids and a new CMY gene variant (blaCMY-108) were found in human isolates.


CONCLUSIONS
This study is one of the first One Health attempts to compare plasmids encoding CMY-2 β-lactamase among clinical isolates from humans and companion animals in the same region. The results indicate an unforeseen heterogeneity of plasmid backgrounds and suggest limited exchange between the two populations, in which blaCMY-2 occurred at very different frequencies and was harboured by distinct plasmid types.
Department of Veterinary Disease Biology, University of Copenhagen, Frederiksberg C, Denmark vbo@sund.ku.dk.
Valeria
V
Bortolaia
Department of Veterinary Disease Biology, University of Copenhagen, Frederiksberg C, Denmark.
Katrine H
KH
Hansen
Department of Veterinary Disease Biology, University of Copenhagen, Frederiksberg C, Denmark.
Christine A
CA
Nielsen
Division of Laboratory Medicine, Marshfield Clinic, Marshfield, WI, USA Department of Microbiology, University of Wisconsin, La Crosse, WI, USA.
Thomas R
TR
Fritsche
Department of Veterinary Disease Biology, University of Copenhagen, Frederiksberg C, Denmark.
Luca
L
Guardabassi
D000818:Animals; D002415:Cats; D004285:Dogs; D004926:Escherichia coli / Q000235:genetics*; D004927:Escherichia coli Infections / Q000453:epidemiology* / Q000382:microbiology; D014644:Genetic Variation; D005838:Genotype; D006801:Humans; D008826:Microbial Sensitivity Tests; D015146:Midwestern United States; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics*; D001618:beta-Lactamases / Q000235:genetics*
C103022:beta-lactamase CMY-2; D001618:beta-Lactamases
AmpC; antimicrobial resistance; cats; dogs