New insights into resistance to colistin and third-generation cephalosporins of Escherichia coli in poultry, Portugal: Novel blaCTX-M-166 and blaESAC genes

The increasing incidence of intestinal colonization with extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae and Gram negative organisms that has been observed in food animals such as poultry, cattle and pigs, are suggestive that animals, food and environment are potential sources of ESBL-producing bacteria. Hence, the aim of this study was to characterized commensal E. coli obtained from healthy broiler and turkey flocks at slaughter for the presence of penicillinases-, ESBL-, extended-spectrum AmpC (ESAC)-, plasmid-mediated quinolone resistance- and MCR-encoding genes. Study of clonal relatedness showed genetic diversity among CTX-M-type, SHV-12 and TEM-52 producing isolates with human isolates of the same type, was also assessed. We detected that eleven (5.4%, 11/202) and forty-five (2.2%, 45/185) E. colt isolates from broilers and turkeys, respectively, carried bla(ESBL) or bla(ESAC) genes and two isolates from turkeys carried mcr-1 gene. A new variant bla(CIX-M-166) was reported in a multidrug resistant isolate from a broiler flock. Overall, we detected a diversity of resistance mechanisms among E. coli from food-producing animals, all of them with high importance at a public health level.