Escherichia coli ST224 and IncF/blaCTX-M-55 plasmids drive resistance to extended-spectrum cephalosporins in poultry flocks in Parana, Brazil

Resistant Enterobacterales of avian intestinal origin can contaminate carcasses during broiler processing and thereby spread through the human food chain. This study aimed at assessing the prevalence, diversity and genomic characteristics of ESBL/AmpC Enterobacterales in poultry flocks from different farms and cities in the state of Paraná, Brazil. Enterobacterales isolated from cloacal samples were subjected to antimicrobial susceptibility testing (AST). ESBL/AmpC isolates were whole-genome sequenced and subjected to S1-nuclease pulsed-field gel electrophoresis (S1-PFGE) followed by Southern blotting to determine the location of resistant genes on plasmids. A surprisingly high proportion of E. coli (40.6 %) collected on non-selective plates presented an ESBL/AmpC phenotype. Multidrug resistance was statistically not higher in ESBL/AmpC E. coli having the potential to be Avian Pathogenic (APEC-like) compared to non-APEC-like ESBL/AmpC E. coli isolates. Resistance to antibiotics not authorized for use in poultry in the State of Paraná was observed, suggesting that antimicrobial resistance (AMR) is co-selected by the use of veterinary-licensed antibiotics. Phylogenetic analyzes revealed the presence of identical or highly similar ESBL/AmpC E. coli clones on farms distant up to 100 km of each other; this strongly suggests that the centralization and verticalization of the poultry industry can facilitate the spread of resistant bacteria among different farms, companies, and cities. The molecular characterization of clones and plasmids proved the dominance of the ST224 E. coli lineage and the IncF/blaCTX-M-55 plasmid, possibly indicating the emergence of successful clones and plasmids adapted to the chicken host. Our data contribute to the epidemiological tracking of resistance mechanisms in Enterobacterales from poultry and to knowledge for further One Health studies to control the spread of resistant bacteria from food animals to humans.