Virulence characteristics and antibiotic resistance analysis of Klebsiella pneumoniae isolated from pig farms in Xinjiang, China: revealing potential zoonotic risks.

Background: This study aimed to analyze the antimicrobial resistance and pathogenicity of Klebsiella pneumoniae(K. pneumoniae) isolates from pigs, evaluate their potential threat to pig farming and public health, and provide a theoretical basis for controlling K. pneumoniae infections in pig farms.

Methods: Nasal swabs collected from pigs were subjected to bacterial isolation, biochemical identification, species-specific PCR, and 16S rRNA sequencing to identify K. pneumoniae. Serotyping and multilocus sequence typing (MLST) were conducted using the wzi and MLST methods, respectively. Biofilm formation was assessed using crystal violet staining. Antimicrobial susceptibility was evaluated via the Kirby-Bauer disk diffusion method, and resistance and virulence genes were identified using PCR. Pathogenicity was determined through string testing and mouse infection models.

Results: 21 strains of K. pneumoniae were isolated and identified from 50 swabs of pig nasal cavities. The isolates were classified into serotypes wzi 19 and wzi 81 and sequence types ST37 and ST967. Ten isolates exhibited strong biofilm-forming ability, while 11 showed moderate biofilm production. Antimicrobial susceptibility testing revealed resistance to β-lactams, aminoglycosides, quinolones, tetracyclines, sulfonamides, aminoalcohols, and glycopeptides, with sensitivity restricted to imipenem and polymyxins. Ten resistance genes and eight virulence genes were detected. Pathogenicity testing in mice revealed a moderate virulence level, with a median lethal dose (LD₅₀) of 4.0 × 10⁶ CFU/mL. Infected mice exhibited significant lesions in the liver, lungs, and small intestine.

Conclusion: These findings highlight a potential risk to pig farming and public health, emphasizing the need for effective control measures against K. pneumoniae infections in pig farms.