Increased Encapsulation and Virulence of Francisella Tularensis Live Vaccine Strain (LVS) by Subculturing on Synthetic Medium

Vaccine. 1994 Jul;12(9):773-5. doi: 10.1016/0264-410x(94)90284-4.


Francisella tularensis live vaccine strain (LVS), taken directly from lyophilized vials, did not appear to have a capsule and had low virulence for Balb/c mice. When this strain was subcultured on Chamberlain's synthetic medium (pH 6.5), it became extensively capsulated (1-5 micron in diameter) and its virulence for Balb/c mice increased about 1000-fold. We conclude that the virulence of the attenuated vaccine strain, F. tularensis LVS, may still be influenced by growth conditions.

MeSH terms

  • Amino Acids / chemistry
  • Animals
  • Bacterial Capsules / immunology
  • Bacterial Capsules / ultrastructure
  • Bacterial Vaccines / immunology*
  • Buffers
  • Culture Media
  • Francisella tularensis / cytology
  • Francisella tularensis / immunology*
  • Francisella tularensis / pathogenicity
  • Freeze Drying
  • Hydrogen-Ion Concentration
  • Mice
  • Mice, Inbred BALB C
  • Microscopy, Electron
  • Tularemia / prevention & control
  • Vaccines, Attenuated / immunology
  • Virulence / immunology


  • Amino Acids
  • Bacterial Vaccines
  • Buffers
  • Culture Media
  • Vaccines, Attenuated