engleski

Intra-vacuolar replication of F. novicida within A. castellanii-pathogenesis of tularemia on in vivo model

Francisella tularensis is a gram negative facultative intracellular bacterium that causes zoonotic disease tularemia. Free living amoeba are environmental host of several intracellular pathogens. It has been shown that F. tularensis utilize A. castellanii as a natural reservoir. For the first time we show that in contrast to mammalian cells, where bacteria replicate in the cytosol, F. novicida resides and replicates within membrane-bound vacuoles within the trophozoites of Acanthamoeba castellanii. In contrast to the transient residence of F. tularensis within acidic compartment within A. castellanii. Based on these studies we investigated the effect of inhaled amoeba on the pathogenesis of tularemia on in vivo model. Balb/c mice were infected intratracheally with F. novicida (106 bacteria per mouse) or were coinculated with F.novicida (106 per mouse) and A. castellanii (106 amoeba per mouse). Suprisingly, coinculation with A. castellanii did not enhanced intracellular replication of F. novicida in mice. Balb/c mice coinfected with A. castellanii develop only mild pneumonia in comparison to mice infected with F. novicida alone, which resulted in severe bronchopneumonia. These studies demonstrating that amoeba play an important reservoir of F. novicida in nature but have a minor role in pathogenesis ot tularemia.

Tularemia; Amoeba; Pathogenesis

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