First Detection of High-Level Aminoglycoside-Resistant Klebsiella pneumoniae and Enterobacter cloacae Isolates Due to 16S rRNA Methyltransferases with and Without blaNDM in Uruguay

Abstract

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 rmtB and armA, but their presence in Uruguay is unknown. Objectives: We describe the genomic characterization of isolates carrying rmtB and rmtC, together with blaNDM-5 and blaNDM-1, respectively, and rmtD 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 con ducted, 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 in compatibility groups, and sequence types. Results: We report three K. pneumoniae ST307 isolates with an IncR plasmid carrying blaNDM-5/blaCTX-M-15/blaTEM-1B/rmtB/dfrA14/dfrA12/sul1/qacE∆1/ermB/mphA, one K. pneumoniae ST258 harboring an IncC plasmid containing rmtC/blaNDM-1/blaCMY-6/aac(6′)-Ib/sul1, and one E. cloacae ST88 isolate with an IncFIB/II plasmid hosting rmtD, within a novel Tn21-like transposon named Tn7825, alongside blaOXA-101/sul1/tet(G)/floR, and a new variant of blaTEM assigned as blaTEM-258. One of the strains, named UH_B2, also carried an IncM1 plasmid encoding qnrE1/blaTEM-1/blaCTX-M-8 associated with ISEcp1. 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.