Emergence of Klebsiella pneumoniae ST14 co-harboring bla_NDM-1, bla_OXA-232, mcr-1.1, and a novel IncI1 tet(X4) plasmid, with evidence of ColKP3 mobilization under antibiotic pressure

Companion animals and environmental niches act as interconnected reservoirs of antimicrobial resistance (AMR) genes, facilitating their persistence and horizontal transfer across hosts and ecosystems. Pet-associated environments, within the One Health framework linking human, animal, and environmental health, remain an underrecognized source of AMR dissemination. Pet grooming facilities generate wastewater containing bacteria from animal skin, fecal matter, and contaminated surfaces, potentially acting as factors that facilitate environmental contamination and zoonotic transmission. Here, we describe the isolation and complete genomic characterization of an extensively drug-resistant Klebsiella pneumoniae strain from wastewater at a pet grooming facility in Bangkok, Thailand. Whole-genome sequencing identified the isolate as sequence type (ST) 14, a globally disseminated high-risk clone associated with multidrug resistance and clinical outbreaks. The strain harbored four clinically significant resistance genes, bla_NDM-1, bla_OXA-232, mcr-1.1, and tet(X4), each located on distinct plasmids. To our knowledge, this is the first report of tet(X4) in K. pneumoniae ST14. The gene was found on a novel IncI1-type plasmid with a composite transposon, suggesting recent acquisition through horizontal gene transfer. Conjugation assays confirmed high transfer efficiency and phenotypic tigecycline resistance. In this study, although bla_OXA-232 was carried on a non-conjugative ColKP3-type plasmid, colistin selection facilitated its transfer with plasmid size expansion, indicating antibiotic-driven mobilization. These findings highlight the evolutionary adaptability of K. pneumoniae ST14 and the risk posed by pet-associated wastewater as a reservoir for clinically important AMR genes. Integrated genomic surveillance and targeted One Health interventions are urgently needed to prevent environmental and zoonotic spread.