First Detection of High-Level Aminoglycoside-Resistant and Isolates Due to 16S rRNA Methyltransferases with and Without in Uruguay.

Background: The increase in antimicrobial resistance includes emerging mechanisms such as 16S ribosomal RNA methylases, which confer high-level resistance to aminoglycosides. In this regard, the most predominant genes observed worldwide are and , but their presence in Uruguay is unknown.

Objectives: We describe the genomic characterization of isolates carrying and , together with and , respectively, and in our country. Methology: Five isolates from patients admitted to three hospitals were studied. Identification and antibiotic susceptibility testing were performed using the Vitek2 System. Whole Genome Sequencing was conducted, and hybrid assembly was performed with Unicycler. In silico analysis using the Center for Genomic Epidemiology's tools was undertaken to predict antibiotic resistance determinants, plasmid incompatibility groups, and sequence types.

Results: We report three ST307 isolates with an IncR plasmid carrying /////////, one ST258 harboring an IncC plasmid containing //// and one ST88 isolate with an IncFIB/II plasmid hosting , within a novel Tn transposon named Tn, alongside ///, and a new variant of assigned as . One of the strains, named UH_B2, also carried an IncM1 plasmid encoding // associated with IS.

Conclusions: This is the first description of plasmids harboring 16S rRNA methyltransferases in Uruguay. The association and dissemination of diverse antibiotic-resistant genes underpin the health threat they represent, highlighting the lack of available antibiotics effective against multidrug-resistant microorganisms.