Occurrence and characterization of blaNDM-5-positive Klebsiella pneumoniae isolates from dairy cows in Jiangsu, China.

OBJECTIVES: To investigate the epidemiological characteristics and the surrounding genetic structure of the blaNDM-5 gene in Klebsiella pneumoniae derived from dairy cows in Jiangsu Province, China.

METHODS: Ten carbapenem-resistant K. pneumoniae were collected from three dairy farms and were screened for the presence of carbapenemase genes using PCR and sequencing. PFGE and MLST were conducted to analyse the genetic relatedness of the blaNDM-5-harbouring K. pneumoniae isolates. The location of blaNDM-5 was identified by S1 nuclease-PFGE and Southern blotting. The transferability and profiles of blaNDM-5-carrying plasmids were analysed by conjugation experiments, and PCR-based replicon typing and RFLP, respectively. The surrounding genetic structure of the blaNDM-5 gene was obtained using WGS and PCR mapping.

RESULTS: All 10 K. pneumoniae from dairy cows harboured the blaNDM-5 gene, exhibited resistance to multiple antimicrobials and belonged to five STs, of which ST1661 and ST2108 were the most prevalent. The blaNDM-5 gene was located on the ∼46 kb IncX3 plasmid in all isolates and these plasmids could be conjugated to an Escherichia coli recipient with no additional resistance profiles transferred. All blaNDM-5-carrying plasmids shared similar genetic contexts and were nearly identical to that of the human K. pneumoniae plasmid (pNDM-MGR194) previously reported in India.

CONCLUSIONS: This was the first case of blaNDM-5-positive K. pneumoniae identified from dairy cows in China. The IncX3 pNDM-MGR194-like plasmid disseminated among cow farms should be highlighted and its potential role in mediating transmission of the blaNDM gene between bacteria from humans and animals requires further monitoring.