Fifteen hypermucoviscous isolates (13 bla_NDM-1-positive) obtained from 11 oncology patients were analyzed by whole genome sequencing, and selected isolates were assessed in a murine model of sepsis. ST395/K2 isolates harboring rmpA, rmpA2, peg-344, aerobactin, enterobactin, yersiniabactin, type I fimbriae, etc. displayed maximal virulence in the mouse lethality assay (LD₅₀ = 10² CFU). ST147/K20 isolates lacking yersiniabactins were relatively less virulent (LD₅₀ = 10⁴ CFU), ST395/K2 isolates lacking rmpA, rmpA2, peg-344, and aerobactin, but harboring yersiniabactin demonstrated minimal virulence (LD₅₀ = 10⁵ CFU). Isolates represent various paths and stages of evolution directed towards convergence of multidrugresistant classical Klebsiella pneumoniae and hypervirulent K. pneumoniae.