LAUSR

Carbapenem-resistant Enterobacteriaceae (CRE) have been rapidly increasing among animals in many countries and have been a great threat to public health. Horse riding is becoming increasingly popular worldwide, however, reports of CRE producing NDM or KPC-2, two prevalent types of carbapenemases, from horses of equestrian club are extremely scarce and KPC-2-producing K. pneumoniae in animals is still rarely characterized. In this study, we identified four NDM-5-producing E. coli isolates from horses in equestrian club in Qingdao, China and one horse possessing NDM-5-producing E. coli also carried ST11 KPC-2-producing K. pneumoniae. Transferability of the plasmids producing carbapenemases was determined by conjugation and the sequences of all CRE isolates and their transconjugants were then analyzed by using whole-genome sequencing. blaNDM-5 was located on a highly similar ~46 kb self-transmissible IncX3 plasmid in all isolates, and these plasmids were nearly identical to IncX3 plasmids from different bacterial species of clinical patients in several countries, even including plasmid from clinical E. coli in Qingdao, China. The chromosome of the ST11 K. pneumoniae in this study was highly similar to ST11 clinical K. pneumoniae reported worldwide including the ST11 KPC-2-producing WCHKP020098 from Chengdu, China, and the blaKPC-2 -bearing plasmid in our study was a novel F33:A-:B- non-conjugative multidrug resistance plasmid. The presence of CRE from horses in equestrian club is alarming due to the potential for transmitting these isolates to humans during horse riding, and the prevalence of CRE among equestrian clubs in the whole country requires further monitoring.