AUTHOR=Alba Patricia , Leekitcharoenphon Pimlapas , Franco Alessia , Feltrin Fabiola , Ianzano Angela , Caprioli Andrea , Stravino Fiorentino , Hendriksen Rene S. , Bortolaia Valeria , Battisti Antonio 

TITLE=Molecular Epidemiology of mcr-Encoded Colistin Resistance in Enterobacteriaceae From Food-Producing Animals in Italy Revealed Through the EU Harmonized Antimicrobial Resistance Monitoring

JOURNAL=Frontiers in Microbiology

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2018.01217

DOI=10.3389/fmicb.2018.01217

ISSN=1664-302X

ABSTRACT=<p>Colistin resistance by mobilisable <italic>mcr</italic> genes has been described in bacteria of food-animal origin worldwide, which has raised public health concerns about its potential foodborne transmission to human pathogenic bacteria. Here we provide baseline information on the molecular epidemiology of colistin-resistant, <italic>mcr</italic>-positive <italic>Escherichia coli</italic> and <italic>Salmonella</italic> isolates in food-producing animals in Italy in 2014-2015. A total 678, 861 and 236 indicator <italic>E. coli</italic>, Extended Spectrum Beta-Lactamase (ESBL)/AmpC-producing <italic>E. coli</italic>, and <italic>Salmonella</italic> isolates, respectively, were tested for colistin susceptibility. These isolates were collected according to the EU harmonized antimicrobial resistance monitoring program and are representative of at least 90 and 80% of the Italian poultry (broiler chickens and turkeys) and livestock (pigs and bovines &lt; 12 months) production, respectively. Whole genome sequencing by Illumina technology and bioinformatics (Center for Genomic Epidemiology pipeline) were used to type 42 <italic>mcr-</italic>positive isolates by PCR. Colistin resistance was mainly observed in the ESBL/AmpC <italic>E. coli</italic> population, and was present in 25.9, 5.3, 6.5, and 3.9% of such isolates in turkeys, broilers, pigs, and bovines, respectively. Most colistin-resistant isolates (141/161, 87.5%) harbored genes of the <italic>mcr</italic>-1 group. <italic>mcr-</italic>1 was also detected in a small proportion of <italic>Salmonella</italic> isolates (3/146, 2.0%) in turkeys. Additional <italic>mcr</italic> types were <italic>mcr</italic>-3 in four ESBL-producing <italic>E. coli</italic> from bovines, and two <italic>mcr</italic>-4 in ESBL (<italic>n</italic> = 1) and indicator <italic>E. coli</italic> (<italic>n</italic> = 1) from pigs and bovines. We describe notable diversity of <italic>mcr</italic> variants with predominance of <italic>mcr-</italic>1.1 and <italic>mcr-</italic>1.2 on conjugative IncX4 plasmids in <italic>E. coli</italic> and in <italic>Salmonella</italic> serovars Typhimurium, Newport, Blockley from turkey. A new variant, <italic>mcr</italic>-1.13 was detected in the chromosome in <italic>E. coli</italic> in turkey and pig isolates. Additionally, we describe <italic>mcr</italic>-3.2 and <italic>mcr</italic>-4.3 in <italic>E. coli</italic> from bovines, and <italic>mcr</italic>-4.2 in <italic>E. coli</italic> from pigs. These findings elucidate the epidemiology of colistin resistance in food-producing animals in Italy along with its genetic background, and highlight the likelihood of <italic>mcr</italic> horizontal transfer between commensal bacteria and major food-borne pathogens (<italic>Salmonella</italic>) within the same type of productions. Thorough action and strategies are needed in order to mitigate the risk of <italic>mcr</italic> transfer to humans, in a “One Health” perspective.</p>