mcr-1 is borne by highly diverse Escherichia coli isolates since 2004 in food-producing animals in Europe.
OBJECTIVE
In November 2015, a plasmid-mediated colistin resistance, MCR-1, was described in animals, food and humans in China, and it was considered as a potential emerging threat to public health. Therefore, we screened for the mcr-1 gene a European collection of colistin-resistant Escherichia coli (n=218) and Salmonella spp. (n=74) isolated from diseased food-producing animals between 2004 and 2014 and characterized the mcr-1-positive clones.


METHODS
Screening for mcr-1 gene was performed by PCR on isolates for which inhibition diameter was <15 mm around a 50 μg disk of colistin. Positive E. coli isolates were then characterized by phylogrouping, multilocus sequence typing and pulsed-field gel electrophoresis typing. Antibiotic susceptibility was determined by disk diffusion testing or by broth microdilution.


RESULTS
Among the collection, 42 E. coli and three Salmonella spp. were positive for mcr-1, with continuous detection since 2004 mainly from bovine and swine digestive infections. Most of the mcr-1-positive strains were resistant to amoxicillin and cotrimoxazole but remained susceptible to cephalosporins, carbapenems and piperacillin/tazobactam. All but one isolate were resistant to colistin, with a minimum inhibitory concentration of >2 mg/L. Most of the mcr-1-positive E. coli belonged to the phylogroup A with two prevalent clonal complexes, CC10 and CC165, in which sequence type 10 and sequence type 100 were overrepresented and pulsed-field gel electrophoresis typing revealed a high diversity of pulsotypes.


CONCLUSIONS
MCR-1 was detected yearly in European food-producing animal since 2004 with a high diversity of pulsotypes supporting the dissemination of mcr-1 via plasmids.
Vétoquinol SA, Global Drug Development Center, Lure, France. Electronic address: farid.elgarch@vetoquinol.com.
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El Garch
Service d'hygiène hospitalière, CHRU Jean Minjoz, 25000 Besançon, France; UMR 6249 CNRS Chrono-environnement, Université de Franche-Comté, 25000 Besançon, France.
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Sauget
Service d'hygiène hospitalière, CHRU Jean Minjoz, 25000 Besançon, France; UMR 6249 CNRS Chrono-environnement, Université de Franche-Comté, 25000 Besançon, France.
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Hocquet
Vétoquinol SA, Global Drug Development Center, Lure, France.
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LeChaudee
Vétoquinol SA, Global Drug Development Center, Lure, France.
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Woehrle
Service d'hygiène hospitalière, CHRU Jean Minjoz, 25000 Besançon, France; UMR 6249 CNRS Chrono-environnement, Université de Franche-Comté, 25000 Besançon, France.
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Bertrand
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D016208:Databases, Factual; D024881:Drug Resistance, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D005060:Europe / Q000453:epidemiology; D015964:Gene Expression Regulation, Bacterial; D008826:Microbial Sensitivity Tests; D012475:Salmonella / Q000235:genetics / Q000378:metabolism
D000900:Anti-Bacterial Agents; D029968:Escherichia coli Proteins; C000614037:MCR-1 protein, E coli
Colistin; Escherichia coli; Food-producing animals; MCR-1; Salmonella spp.