Molecular Epidemiology and Antimicrobial Resistance of Klebsiella pneumoniae Strains Isolated From Dairy Cows in Xinjiang, China.

BACKGROUND

Klebsiella pneumoniae is an opportunistic pathogen that causes severe infections in humans and animals. Nonetheless, little is known about the molecular epidemiology of mastitis-associated K. pneumoniae in dairy cows.

OBJECTIVES

This cross-sectional study investigated the epidemiology and antimicrobial resistance (AMR) of K. pneumoniae in 700 milk samples collected from cows with and without mastitis in seven dairy farms in Xinjiang, China.

METHODS

K. pneumoniae was identified by PCR amplification of the khe gene and the automated VITEK 2 Compact System. Resistance against 18 antimicrobial agents was analysed by broth microdilution. Forty-four new strains were sequenced by whole-genome sequencing (WGS). WGS data were searched for the presence of AMR and virulence genes. Genotypic characterization was performed by multilocus sequence typing and the analysis of wzi allele types and K and O antigens.

RESULTS

K. pneumoniae isolates were found in 131 samples (18.7%). The prevalence of K. pneumoniae in cows with clinical and subclinical mastitis was higher than that in healthy cows (27.1%, 23.2% and 7.3%, respectively). WGS identified 27 wzi allele types, 16 K antigen serotypes, 6 O antigen serotypes and 25 sequence types. Phylogenetic analysis showed high genomic diversity in K. pneumoniae. The rate of resistance to tetracycline and cefazolin was 39.7% and 31.3%, and the multidrug resistance rate was 26.7%. Thirty-nine AMR genes conferring resistance to nine antibiotic classes and 57 virulence genes were identified in new isolates. AMR and virulence genes were more prevalent in known human isolates than in new isolates.

CONCLUSIONS

These results improve our understanding of the epidemiology and resistance status of mastitis-associated K. pneumoniae strains. The emergence and spread of multidrug-resistant K. pneumoniae strains threaten food safety and public health.