The role of K antigens as virulence factors in Klebsiella

J Med Microbiol. 1986 Mar;21(2):133-7. doi: 10.1099/00222615-21-2-133.


The importance of K antigen of Klebsiella as a virulence factor was studied in nine pairs of K+ and K- strains, each pair isogenic apart from the presence of K antigen. Loss of K antigen by nine K+ strains resulted in the reduced virulence of their K- variants in a mouse-skin model. This reduced virulence of K- strains for mice may be explained in all strains by a higher degree of phagocytosis as measured by chemiluminescence response of human polymorphonuclear leukocytes (PMNL) and in most strains by enhanced killing by either human PMNL or human serum or both. Although the protective role of the K antigen in serum-induced killing and killing by PMNL was generally evident, our results also suggested that other virulence factors were sometimes involved.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antigens, Bacterial*
  • Antigens, Surface*
  • Blood Bactericidal Activity
  • Klebsiella pneumoniae / genetics
  • Klebsiella pneumoniae / growth & development
  • Klebsiella pneumoniae / immunology
  • Klebsiella pneumoniae / pathogenicity*
  • Luminescent Measurements
  • Mice
  • Mutation
  • Neutrophils / immunology
  • Neutrophils / metabolism
  • Phagocytosis
  • Virulence


  • Antigens, Bacterial
  • Antigens, Surface
  • K antigens