Genetic Characteristics and Microbiological Profile of Hypermucoviscous Multidrug-Resistant Klebsiella variicola Coproducing IMP-4 and NDM-1 Carbapenemases.

We report here a hypermucoviscous, New Delhi metallo-β-lactamase 1 (NDM-1) and imipenemase 4 (IMP-4) carbapenemases-coproducing Klebsiella variicola isolate obtained from a pediatric patient. This strain was resistant to carbapenems and most other β-lactams. Although hypermucoviscous, this strain possessed attenuated virulence according to serum killing assay and Galleria mellonella infection model. Notably, two copies of were contained on two tandem IS elements and coexisted with in a novel hybrid multidrug resistance plasmid. This is the first description of the coexistence of and in a single plasmid of hypermucoviscous K. variicola. As an important member of the Klebsiella pneumoniae complex, Klebsiella variicola is poorly studied as an emerging human pathogen. We, for the first time, report a unique isolated from a pediatric patient in China. This isolate exhibited hypermucoviscosity, a classic hypervirulence characteristic of K. pneumoniae, and contained multiple carbapenem-resistant genes, including and . Interestingly, these antimicrobial resistance genes were located on a novel hybrid plasmid, and our results suggested that this plasmid might have been introduced from K. pneumoniae and undergone a series of integration and recombination evolutionary events. Overall, our study provides more insight into . and highlights its superior capability to acquire and maintain foreign resistance genes.