Emergence of tet(X4)-positive hypervirulent Klebsiella pneumoniae of food origin in China

The emergence of hypervirulent Klebsiella pneumoniae (hvKp) poses a great threat to human health, while tigecycline provides an important guarantee for the treatment of MDR-hvKp infections. Currently, prevalence of tet(X4)-positive hvKp in animal origin remains unknown. Six tet(X4)-positive K. pneumoniae isolates were isolated from pork samples in China. Notably, one of them was identified as a hvKp isolate. This isolate has a hypermucoviscous and a hypervirulent phenotype according to string test and mouse infection model. The tet(X4) gene in six K. pneumoniae isolates was located on an IncFII(pCRY) plasmid. Interestingly, the backbone structure of IncFII(pCRY) tet(X4)-positive plasmid was similar to that of bla_KPC-2-positive plasmid in hvKp. Besides, this IncFII(pCRY) plasmid can be transferred into E. coli and ST11 hvKp, and does not incur a significant fitness cost, and is able to persist stably. A novel tet(X4) core genetic environment (abh-tet(X4)-IS102-1-ISCR2) was found on the plasmid. To the best of our knowledge, this is the first report of tet(X4)-positive hvKp in animals. Our findings highlight the urgent need for further global surveillance of tet(X4)-positive hvKp in clinical and animal farming settings with the One Health approach.