Emergence of a New ST617 Hypervirulent Klebsiella pneumoniae with ESBL ⁺ and Strong Biofilm Forming Ability in China

The increasing infections caused by hypervirulent Klebsiella pneumoniae (hvKP) resistant to carbapenem, broad-spectrum β-lactam and colistin has posed great challenges to global public health. However, the typing and detailed molecular features of the multi-drug resistant hvKP remain to be improved. Here, we characterized a broad-spectrum β-lactam-resistant K. pneumoniae ST617 isolate that has not been previously reported to cause severe disease in China. We obtained the whole-genome sequence of one K. pneumoniae ST617 isolate—HZ7—from a patient with bile duct infection. Phylogenetic reconstruction was performed to investigate the possible host evolutionary origin of HZ7, and the virulence property was studied in comparison with the nearest ST617 neighbours—YZ strains isolated from patient blood infections. Our studies indicated that the HZ7 is an ESBL + Kp that is likely evolved from environmental or animal-derived sources. Importantly, the virulence assay showed that HZ7 was highly virulent and compared with the well known hvKP strain—NTUH-K2044 and the highly virulent clinical strain ST11-K64—HZ54—isolated from a patient with severe pneumonia. In addition, HZ7 showed strong biofilm formation ability. Whole-genome sequencing analysis identified seven potential virulence genes in HZ7: kp7_000748, kp7_002156, kp7_002157, kp7_002158, kp7_002159, kp7_003103, kp7_003104, which are absent in K. pneumoniae patient isolates from Yangzhou and the environmental samples. Finally, transcriptomic analysis of HZ7 identified six genes— wcaJ, fimA, mrkH, pgaA, ugd , and gndA that are associated with biofilm formation. Given its high virulence likely associated with the seven unique genes acquired via horizontal transfer and strong biofilm forming ability, this strain should be closely monitored to prevent wider spread in the clinic.