Hypervirulent (Hypermucoviscous) Klebsiella Pneumoniae: A New and Dangerous Breed

Virulence. 2013 Feb 15;4(2):107-18. doi: 10.4161/viru.22718. Epub 2013 Jan 9.


A new hypervirulent (hypermucoviscous) variant of Klebsiella pneumoniae has emerged. First described in the Asian Pacific Rim, it now increasingly recognized in Western countries. Defining clinical features are the ability to cause serious, life-threatening community-acquired infection in younger healthy hosts, including liver abscess, pneumonia, meningitis and endophthalmitis and the ability to metastatically spread, an unusual feature for enteric Gram-negative bacilli in the non-immunocompromised. Despite infecting a healthier population, significant morbidity and mortality occurs. Although epidemiologic features are still being defined, colonization, particularly intestinal colonization, appears to be a critical step leading to infection. However the route of entry remains unclear. The majority of cases described to date are in Asians, raising the issue of a genetic predisposition vs. geospecific strain acquisition. The traits that enhance its virulence when compared with "classical" K. pneumoniae are the ability to more efficiently acquire iron and perhaps an increase in capsule production, which confers the hypermucoviscous phenotype. An objective diagnostic test suitable for routine use in the clinical microbiology laboratory is needed. If/when these strains become increasingly resistant to antimicrobials, we will be faced with a frightening clinical scenario.

Keywords: Klebsiella pneumoniae; diagnosis; epidemiology; hypermucoviscous; hypervirulent; infection; pathogenesis; treatment; virulence factors.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Review

MeSH terms

  • Age Factors
  • Bacterial Capsules / metabolism
  • Community-Acquired Infections / epidemiology
  • Community-Acquired Infections / microbiology
  • Community-Acquired Infections / mortality
  • Community-Acquired Infections / pathology
  • Endophthalmitis / microbiology
  • Endophthalmitis / pathology
  • Genetic Predisposition to Disease
  • Global Health
  • Humans
  • Iron / metabolism
  • Klebsiella Infections / epidemiology
  • Klebsiella Infections / microbiology*
  • Klebsiella Infections / mortality
  • Klebsiella Infections / pathology*
  • Klebsiella pneumoniae / pathogenicity*
  • Liver Abscess / microbiology
  • Liver Abscess / pathology
  • Meningitis, Bacterial / microbiology
  • Meningitis, Bacterial / pathology
  • Pneumonia, Bacterial / microbiology
  • Pneumonia, Bacterial / pathology
  • Virulence
  • Virulence Factors / metabolism


  • Virulence Factors
  • Iron