Revealing mcr-1-positive ESBL-producing Escherichia coli strains among Enterobacteriaceae from food-producing animals (bovine, swine and poultry) and meat (bovine and swine), Portugal, 2010-2015

We screened 1840 Enterobacteriaceae isolates from food-producing animals, meat, meat products and animal feed, for the detection of plasmid-mediated colistin resistance, during 2010-2015. The mcr-1 gene was detected in 8.0% (97/1206) Escherichia coli and in 0.47% (3/634) Salmonella enterica isolates, with a high number of mcr-1 positive E. coli isolates (45.7%) being extended-spectrum β-lactamase or plasmid-mediated AmpC β-lactamase co-producers. No mcr-2 gene was detected. Our findings highlight the spread of mcr-1 genes within a wide-ranging sample of food-producing animals and meat, in Portugal.Highlights: Spread of MCR-1 within a wide-ranging sample of food-producing animals and meat; Occurrence of mcr genes in E. coli isolates from turkeys, swine and broilers; High number of mcr positive E. coli isolates that were ESBL or PMAβ co-producers; First description of MCR-1-producing Salmonella Reading from bovine meat; New mcr-1.9 variant reported in an Escherichia coli from a swine.V. Manageiro was supported by Fundação para a Ciência e a Tecnologia (FCT) fellowship (grant SFRH/BPD/77486/2011), financed by the European Social Funds (COMPETE-FEDER) and national funds of the Portuguese Ministry of Education and Science (POPH-QREN). The authors also thank to FCT for project grant UID/MULTI/00211/2013.