Molecular insight into hypervirulent Klebsiella pneumoniae from North India

Hypervirulent Klebsiella pneumoniae (hvKp) is an emerging pathotype capable of causing tissue-invasive, community- acquired infections in healthy individuals across all age groups. This strain is characterized by hypermucoviscosity and the presence of specific virulence biomarker genes, which contribute to its enhanced pathogenicity compared to classical Klebsiella pneumoniae (cKp). For better patient care and epidemiological research, we need a reliable test to find hvKp strains. Therefore, it is of interest to differentiate between cKp and hvKp strains by assessing hypermucoviscosity using the string test (≥5 mm string length) and detecting virulence biomarkers via PCR assay. Among 100 isolates, 37 (37%) tested positive for the string test and molecular analysis identified 28 (28%) as hvKp. Of the 28% hvKp strains, 13 (46.4%) exhibited hypermucoviscosity and hypervirulence. All hvKp strains 28 (100%) carried at least one siderophore biosynthesis gene (iucA, iucB and iroB), 23 (82.1%) were positive for mucoid phenotype genes (rmpA, rmpA2), and 11 (39.2%) harbored the peg344 gene encoding a putative metabolite transporter. Notably, 5 (17.9%) hvKp strains possessed all six major virulence genes (rmpA, rmpA2, iucA, iucB, iroB and peg344). Thus, we show that virulence biomarkers such as siderophore biosynthesis and mucoid phenotype genes are critical for identifying hvKp strains. The integration of hypermucoviscosity and hypervirulence underscores the necessity for focused research and heightened clinical vigilance to combat this emerging threat.