Co-Occurrence of Two Plasmids Encoding Transferable and (Y) Genes in Carbapenem-Resistant .

has emerged as a significant human pathogen, acquiring multiple antibiotic resistance genes, including carbapenemases. This study focuses on characterizing the plasmids harboring the and (Y) genes in two carbapenem-resistant isolates (UCO-553 and UCO-554) obtained in Chile during the COVID-19 pandemic. : Antibiotic susceptibility testing was conducted on UCO-553 and UCO-554. Both isolates underwent whole-genome sequencing to ascertain their sequence type (ST), core genome multilocus sequence-typing (cgMLST) profile, antibiotic resistance genes, plasmids, and mobile genetic elements. Conjugation experiments were performed for both isolates. : Both isolates exhibited broad resistance, including resistance to carbapenems, third-generation cephalosporins, fluoroquinolones, tetracycline, cotrimoxazole, and aminoglycosides. Both isolates belong to sequence type ST1761, with a difference of 17 out of 2984 alleles. Each isolate carried a 47,274 bp plasmid with and genes and two highly similar plasmids: a 35,184 bp plasmid with (Y), , , and genes, and a 6078 bp plasmid containing the gene. Quinolone-resistance mutations were identified in the and genes of both isolates. Importantly, was located within a Tn transposon, and (Y) was embedded in a Tn transposon. Conjugation experiments successfully transferred and (Y) into the ATCC 19606 strain, indicating the potential for horizontal gene transfer. : This study highlights the critical role of plasmids in disseminating resistance genes in and underscores the need for the continued genomic surveillance of this emerging pathogen. The findings emphasize the importance of monitoring for its potential to cause difficult-to-treat infections and its capacity to spread resistance determinants against clinically significant antibiotics.