Characterization of aminoglycoside resistance in multidrug-resistant Klebsiella pneumoniae isolates.

Multidrug-resistant (MDR) Klebsiella pneumoniae, particularly the lineages resistant to carbapenems and aminoglycosides, is an escalating global public health threat across human, animal, and environmental reservoirs. We examined phenotypic and genetic features of MDR K. pneumoniae isolates. A total of 70 K. pneumoniae strains were collected from clinical (n=55), environmental (n=7), and animal (n=8) sources. To better understand the evolutionary relationship between these isolates, a phylogenetic analysis was performed alongside 35 publicly available K. pneumoniae genomes from NCBI and Pathogenwatch. Whole-genome sequencing (WGS) revealed that 43 isolates carried the blaKPC gene, including blaKPC-2 and blaKPC-3 variants, with different susceptibility profiles to aminoglycosides. Among all isolates, 84% (n = 59/70) were resistant to amikacin and 53% (n = 37/70) were resistant to gentamicin. Aminoglycoside resistance was primarily associated with aminoglycoside-modifying enzymes, including aph(3')-Ia (52%), aac(3)-IIa/aadA2 (49%), and aac(6')-Ib-cr (37%). Additionally, 16S rRNA methyltransferases rmtB and rmtG were detected in 14% of isolates and were associated with high-level amikacin MICs. Overall, 81% of strains were non-susceptible to at least one aminoglycoside, underscoring the clinical importance of these determinants. Phylogenetic analysis based on WGS data showed two main clusters (A and B), and the multilocus sequence type ST11 predominated among Brazilian isolates. Our findings showed a heterogeneous distribution of sequence type profiles across the two clusters and a close relationship between K. pneumoniae strains from human, animal, and environmental sources, highlighting the need for integrated One Health surveillance.