Francisella tularensis and pathogenesis of tularemia

F. tularensis is a gram negative, highly infectious, facultative intracellular bacterium that causes fulminating disease tularemia. The genus Francisella includes four organisms: F. tularensis subsp. tularensis (type A), F. tularensis subsp. holarctica (type B), F. tularensis subsp. mediasiatica and Francisella subsp. novicida. The ability of F. tularensis to envade and proliferate within cells was shown to be of great relevance for the development of tularemia. F. tularensis is able to survive and replicate within various cell types but macrophages are the key cells in pathogenesis of tularemia.