Isolation, identification, and drug - resistance analysis of Klebsiella pneumoniae from eight pig farms in different regions of China

This study investigated the epidemiological and molecular characteristics of Klebsiella pneumoniae isolated from large-scale pig farms across eight regions nationwide. A total of 329 nasal swab samples were collected between September and November 2024, yielding 70 K. pneumoniae isolates, including 6 ESBL-producing strains. Antimicrobial susceptibility testing showed widespread multidrug resistance: all isolates were fully resistant to seven antibiotics (including amoxicillin, ofloxacin, and fosfomycin) but remained fully susceptible to tigecycline; one isolate displayed resistance to meropenem. Resistance gene screening identified high prevalence of acrA, acrB, blaSHV, tetA, and sul2. Virulence assays indicated that hypervirulent K. pneumoniae was not detected. Genotyping revealed substantial diversity (37 wzi alleles and 36 MLST sequence types), including six potential novel STs. Whole-genome sequencing was used to further characterize ESBL-producing and carbapenem-resistant isolates and to infer their phylogenetic relationships. Overall, the results highlight an increasing burden of antimicrobial resistance in K. pneumoniae from pig farms and support the development of evidence-based antimicrobial stewardship and clinical treatment guidelines in swine production.