Hypervirulent
carbapenem-resistant Klebsiella pneumoniae (hv-CRKP) has recently aroused increasing attention, especially ST11, the predominant CRKP clone in China. Here, we report a case of hv-CRKP-associated
infection and reveal the in-host evolution of its mechanism of resistance to
tigecycline and
polymyxin under clinical
therapy. A total of 11 K. pneumoniae
carbapenemase (KPC)-producing CRKP strains were consecutively isolated from a male patient who suffered from continuous and multisite
infections. String and antimicrobial susceptibility tests identified seven hypermucoviscous strains and three
tigecycline-resistant and four
colistin-resistant strains. Galleria mellonella larvae
infection model confirmed the hypervirulence. Pulsed-field gel electrophoresis (PFGE) separated three PFGE clusters among all strains, and further Southern blotting detected that blaKPC-2 was located on the same-sized plasmid. Whole-genome sequencing showed that all strains belonged to the hv-CRKP ST11-KL64 clone. Diverse hypervirulence factors and resistance genes were identified. Further sequencing with the Nanopore platform was performed on the CRKP-Urine1 strain, which contained one virulence plasmid (pVi-CRKP-Urine1) and two resistance plasmids (pKPC-CRKP-Urine1 and pqnrS1-CRKP-Urine1). The gene mutations responsible for
tigecycline or
colistin resistance were then amplified with PCR followed by sequencing, which indicated that mutations of ramR and lon were the potential loci for
tigecycline resistance and that the pmrB, phoQ and mgrB genes for
colistin resistance. A novel frameshift mutation of lon was identified in the high-level
tigecycline-resistant strain (MIC, 128 mg/L). The results indicate that the hypervirulent ST11-KL64 clone is a potential threat to antiinfection treatment and is capable of rapid and diverse evolution of resistance during
tigecycline and
polymyxin treatment.