Identification of Klebsiella pneumoniae virulence determinants using an intranasal infection model

Mol Microbiol. 2005 Nov;58(4):1054-73. doi: 10.1111/j.1365-2958.2005.04918.x.


Klebsiella pneumoniae is a Gram-negative enterobacterium that has historically been, and currently remains, a significant cause of human disease. It is a frequent cause of urinary tract infections and pneumonia, and subsequent systemic infections can have mortality rates as high as 60%. Despite its clinical significance, few virulence factors of K. pneumoniae have been identified or characterized. In this study we present a mouse model of acute K. pneumoniae respiratory infection using an intranasal inoculation method, and examine the progression of both pulmonary and systemic disease. Wild-type infection recapitulates many aspects of clinical disease, including significant bacterial growth in both the trachea and lungs, an inflammatory immune response characterized by dramatic neutrophil influx, and a steady progression to systemic disease with ensuing mortality. These observations are contrasted with an infection by an isogenic capsule-deficient strain that shows an inability to cause disease in either pulmonary or systemic tissues. The consistency and clinical accuracy of the intranasal mouse model proved to be a useful tool as we conducted a genetic screen to identify novel virulence factors of K. pneumoniae. A total of 4800 independent insertional mutants were evaluated using a signature-tagged mutagenesis protocol. A total of 106 independent mutants failed to be recovered from either the lungs or spleens of infected mice. Small scale independent infections proved to be helpful as a secondary screening method, as opposed to the more traditional competitive index assay. Those mutants showing verified attenuation contained insertions in loci with a variety of putative functions, including a large number of hypothetical open reading frames. Subsequent experiments support the premise that the central mechanism of K. pneumoniae pathogenesis is the production of a polysaccharide-rich cell surface that provides protection from the inflammatory response.

Publication types

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

MeSH terms

  • Animals
  • Bacteremia / microbiology
  • Bacteremia / pathology
  • Bacterial Capsules / immunology
  • Colony Count, Microbial
  • Disease Models, Animal
  • Female
  • Genes, Bacterial
  • Klebsiella Infections / microbiology*
  • Klebsiella Infections / pathology
  • Klebsiella pneumoniae / genetics
  • Klebsiella pneumoniae / pathogenicity*
  • Lung / microbiology
  • Lung / pathology
  • Mice
  • Mutagenesis, Insertional
  • Open Reading Frames / genetics
  • Pneumonia, Bacterial / microbiology
  • Pneumonia, Bacterial / pathology
  • Respiratory Tract Infections / microbiology*
  • Respiratory Tract Infections / pathology
  • Spleen / microbiology
  • Trachea / microbiology
  • Trachea / pathology
  • Uronic Acids / analysis
  • Virulence Factors / analysis*


  • Uronic Acids
  • Virulence Factors