Molecular Insights Into Hypervirulent Klebsiella pneumoniae: Identification and Correlation of Virulence Determinant

Klebsiella pneumoniae is an increasingly important opportunistic pathogen worldwide, particularly due to the emergence and spread of hypervirulent K. pneumoniae (hvKP), a clinically significant pathotype first identified in Taiwan. This study aimed to molecularly identify hvKP isolates screened for coexisting virulence determinants and evaluate the association between specific virulence genes and hypervirulence. Clinical specimens were collected from hospitalized patients, and K. pneumoniae isolates were identified phenotypically using microscopic culture characteristics and biochemical assays and genotypically confirmed by PCR targeting the khe gene. Hypermucoviscosity regulators prmpA and prmpA2, siderophore-encoding genes iucA and iroN, and other virulence-associated genes including wzi, magA, wzyK2, wabG, and peg-344 were investigated. Eighty-two capsulated non-motile K. pneumoniae isolates were confirmed with prmpA and prmpA2 detected in 42 and 29 isolates, respectively, whereas iucA was identified in 31 isolates and iroN in 6 isolates only. Based on the molecular criteria, 34 isolates were classified as hvKP and 48 as classical K. pneumoniae (cKP). A strong association was observed between the peg-344 gene and hypervirulence (p = 0.0001), whereas hypermucoviscosity showed a weaker correlation. However, low-speed sedimentation assay (LSSA) analysis demonstrated a significant relationship between the hypermucoviscous phenotype and genotypic hypervirulence (p = 0.041). These findings highlight the molecular determinants of hvKP and identify peg-344 as the gene most strongly associated with hypervirulence; however, its moderate sensitivity (58.8%) and absence in over 40% of hvKP isolates indicate that it is better suited as a supportive confirmatory marker than a standalone diagnostic biomarker for hvKP.