Five-Biomarker Definition for Hypervirulent Klebsiella pneumoniae Bloodstream Infection and Abscess Complications, Japan, 2022-2024.

Hypervirulent Klebsiella pneumoniae (hvKp) is an emerging cause of invasive infection, but clinical relevance of a 5-biomarker genotypic definition remains unclear. We analyzed 207 episodes of K. pneumoniae bloodstream infection at a tertiary hospital in Japan during 2022-2024. We defined hvKp by PCR detection of all 5 biomarkers: rmpA, rmpA2, iucA, iroB, and peg-344. Overall, hvKp accounted for 14% (28/207) of episodes. Abscess complications occurred in 61% (17/28) of hvKp episodes and 13% (23/179) of classical K. pneumoniae episodes. hvKp case-patients had longer median hospitalization (28 vs. 14 days) and duration of antimicrobial drug treatment (43 vs. 14 days) than those with classical K. pneumoniae. Most (9/10) sequence type 23 hvKp episodes involved abscesses. Short-read whole-genome sequencing detected CTX-M-type extended-spectrum β-lactamase genes in 11% (3/28) of hvKp isolates, representing 1.4% (3/207) of all K. pneumoniae episodes. The 5-biomarker definition delineated a clinically distinct subgroup, demonstrating its value for genomic surveillance of emerging hvKp.