Klebsiella species isolated from diseased dogs in Brazil reveal multidrug resistance, CTX-M-15 predominance and detection of a KPC-2-producing ST11 Klebsiella pneumoniae isolate

Abstract Objectives To investigate the antimicrobial resistance, β-lactamase genes, biofilm formation, and genomic characteristics of Klebsiella species isolated from diseased dogs in southeastern Brazil. Methods Fifty-five Klebsiella isolates from dogs with clinical infections were identified by MALDI‒TOF MS. Antimicrobial susceptibility was assessed by disk diffusion. ESBL and carbapenemase genes were detected by PCR. Biofilm formation was evaluated using a microtiter plate assay. The only blaKPC-positive isolate underwent whole-genome sequencing and phylogenetic analysis with publicly available Brazilian genomes. Results K. pneumoniae was the predominant species (74.5%), followed by K. variicola (20%). Multidrug resistance was observed in 36.4% of the K. pneumoniae isolates. High resistance rates of the isolates were observed for fluoroquinolones, cephalosporins, and sulfonamides, whereas chloramphenicol showed moderate susceptibility. The most frequent β-lactamase genes were blaTEM-1 (34.5%) and blaCTX-M-15 (30.9%). A single isolate (1.8%) harbored blaKPC. No hypervirulence-associated genes were detected. All the isolates formed biofilms, predominantly with weak to moderate adhesion. Whole-genome sequencing of the blaKPC-positive isolate revealed K. pneumoniae ST11 (CG340) carrying multiple resistance genes, including blaKPC-2, and clustering with human-associated genomes within a high-risk lineage. Conclusions Multidrug-resistant K. pneumoniae, including a high-risk ST11 blaKPC-2-producing clone, was identified in diseased dogs, supporting the need to investigate companion animals as possible reservoirs of clinically relevant antimicrobial resistance determinants. The combination of multidrug resistance and biofilm formation highlights the importance of continued surveillance and prudent antimicrobial use within One Health.