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

Colistin resistance by mobilisable 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, -positive and isolates in food-producing animals in Italy in 2014-2015. A total 678, 861 and 236 indicator , Extended Spectrum Beta-Lactamase (ESBL)/AmpC-producing , and 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 < 12 months) production, respectively. Whole genome sequencing by Illumina technology and bioinformatics (Center for Genomic Epidemiology pipeline) were used to type 42 positive isolates by PCR. Colistin resistance was mainly observed in the ESBL/AmpC 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 -1 group. 1 was also detected in a small proportion of isolates (3/146, 2.0%) in turkeys. Additional types were -3 in four ESBL-producing from bovines, and two -4 in ESBL ( = 1) and indicator ( = 1) from pigs and bovines. We describe notable diversity of variants with predominance of 1.1 and 1.2 on conjugative IncX4 plasmids in and in serovars Typhimurium, Newport, Blockley from turkey. A new variant, -1.13 was detected in the chromosome in in turkey and pig isolates. Additionally, we describe -3.2 and -4.3 in from bovines, and -4.2 in 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 horizontal transfer between commensal bacteria and major food-borne pathogens () within the same type of productions. Thorough action and strategies are needed in order to mitigate the risk of transfer to humans, in a "One Health" perspective.