Emergence and Clonal Spread of CTX-M-65-Producing From Retail Meat in Portugal.

The emergence and dissemination of resistance to third- and fourth-generation cephalosporins among from different sources impose a global public health threat. Here, we characterized by whole-genome sequencing four strains harboring the gene identified among 49 isolates from beef and pork collected at retail. The genomic content was determined using the Center for Genomic Epidemiology web tools. Additionally, the prediction and reconstruction of plasmids were conducted, the genetic platform of the genes was investigated, and phylogenetic analysis was carried out using 17 other genomes with the same sequence type and harboring the gene. All strains harbored , , and , and one also carried the gene. Other resistance genes, namely, , , , , , and , were present in all the genomes; the -1.1 gene was identified in the colistin-resistant strains. They belong to sequence type 2179, phylogenetic group B1, and serotype O9:H9 and carried plasmids IncI, IncFIC(FII), and IncFIB. All strains share an identical genetic environment with IS and IS flanking the gene. It seems likely that the gene is located in the chromosome in all isolates based on deep analysis. Our findings showed that the strains are clonally related and belong to two sub-lineages. This study reports the emergence of CTX-M-65-producing in Portugal in food products of animal origin. The chromosomal location of the gene may ensure a stable spread of resistance in the absence of selective pressure.