Extended‐spectrum β‐lactamase (ESBL) and carbapenemase‐producing Klebsiella spp., particularly K. pneumoniae , are emerging threats in both clinical and community settings. To investigate the epidemiology, phylogenetics, and antimicrobial resistance of bovine‐origin strains, 174 bacterial isolates were obtained from 180 mastitic milk samples across eight dairy farms in Henan Province. Sixty‐five isolates were identified as Klebsiella spp., including 61 K. pneumoniae , 2 K. quasipneumoniae , 1 K. oxytoca , and 1 K. michiganensis . Phylogenetic analysis assigned most isolates to the KpI phylogroup, and multilocus sequence typing revealed 24 sequence types, with ST107 and ST1083 predominating. SNP‐based phylogeny indicated two major clades with evidence of clonal spread. Compared with human hypervirulent reference strains, bovine isolates were genetically distinct, lacking key virulence genes rmpA , iuc , and iro , while only a minority carried ybt . Among the 65 Klebsiella isolates, 31 (47.7%) were ESBL producers, mainly carrying bla CTX-M−3 or bla CTX-M−15 , one K. pneumoniae isolate harbored the carbapenemase‐encoding gene bla NDM−1 . ESBL producers showed >90% resistance to β‐lactams but remained largely susceptible to ciprofloxacin and gentamicin, with 87.1% displaying multidrug resistance. Co‐occurrence of multiple resistance and virulence determinants was observed, and the dissemination of bla CTX-M genes was strongly associated with the mobile element IS Ecp1 . Plasmid analysis revealed that bla CTX-M genes were primarily located on IncFIB(K) plasmids, while the bla NDM−1 ‐positive isolate carried a transferable IncC2 plasmid. SNP analysis further supported clonal dissemination among isolates with identical STs. These findings demonstrate that dairy cattle serve as important reservoirs of multidrug‐resistant Klebsiella , where resistance is driven by both clonal transmission and plasmid‐mediated horizontal transfer. This highlights potential risks for animal health, antimicrobial stewardship, and zoonotic transmission to humans.
Feng et al. (Thu,) studied this question.
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