Purpose: Pandrug-resistant K. pneumoniae  is still rare in China, and the lack of studies limits our understanding of the emergence mechanism of pandrug-resistant K. pneumoniae . Here, we report the rapid emergence of a pandrug-resistant K. pneumoniae  ST11 strain in an inpatient after treatment with multiple broad-spectrum antibiotics in China.
Patients and Methods: K. pneumoniae  strain KP65 was isolated from a 55-year-old male patient hospitalized in the Department of Intensive Care Unit (ICU) of a teaching hospital in China. Antimicrobial susceptibility testing was conducted according to the guidelines of the Clinical and Laboratory Standards Institute (CLSI). The complete genome sequence of the strain was determined using the Illumina NovaSeq 6000 platform and long-read MinION sequencer. Genomic features and resistance mechanisms of the strain were comprehensively analysed using various bioinformatics approaches.
Results: K. pneumoniae  strain KP65 was found to be resistant to all antibiotics tested, including beta-lactams, aminoglycosides, quinolones, tigecycline and colistin. Seven resistance genes were identified in the genome. The carbapenem-resistant gene bla _KPC-2 and extended-spectrum β-lactamase (ESBL)-producing gene bla _CTX-M-65 are located on the IncFII-type plasmid pKPC-2-KP65. No mcr  genes were detected in the genome, but an IS 5  insertion element was found at position 117 of the mgrB  gene. Regarding the rpsJ  gene, single-base substitution, G169C, leading to the amino acid substitution V57L was also identified. According to in silico MLST analysis, K. pneumoniae  KP65 belongs to sequence type ST11. The closest relative of K. pneumoniae  KP65 is another ST11 K. pneumoniae  strain, which was isolated from a bloodstream infection in Hangzhou, differing by only 53 cgMLST loci.
Conclusion: Under the selective pressure of antibiotics, the KPC-2-producing K. pneumoniae  ST11 strain can easily evolve pandrug resistance through chromosomal mutations. More attention is required to monitor the prevalence of the KPC-2-producing K. pneumoniae  ST11 strain in China.
Keywords: Klebsiella pneumoniae , mgrB , rpsJ , ST11, bla _KPC-2