engleski

Coinculation of Acanthamoeba castellanii and Francisella novicida in a mice model

Epidemiology of F. tularensis in various parts of the world is associated with water-borne transmission, which includes mosquitoes and amoebae as the potential host reservoirs of the bacteria in water resources. In vitro studies showed intracellular replication of F. tularensis within A. castellanii and H. vermiformis cells. Whether ameba is a biological reservoir for Francisella in the environment and the role of F. tularensis-infected protozoa in the pathogenesis of human infection is not known. We used the 24 h coculture of A. castellanii and F. novicida for investigation of the effect of inhaled amoeba on the pathogenesis of tularemia on in vivo model. Balb/c mice were infected intratracheally with F. novicida (10 3 bacteria per mouse) or were coinculated with F. novicida (10 3 per mouse) and A. castellanii (10 4 amoeba per mouse). Surprisingly, coinculation with A. castellanii did not enhanced intracellular replication of F. novicida in mice. Balb/c mice injected with F. novicida-infected A. castellanii develop only mild pneumonia in comparison to mice infected with F. novicida alone, which resulted in severe bronchopneumonia. Upon inhalation, F. novicida infects a variety of host cells, though neutrophils are the predominant cells early during infection in the lung infiltrates of pulmonary tularemia. The F. novicida-infected A. castellanii was probably taken up by neutrophils more rapidly following inhalation, and this apparently occurs without significant recruitment of new neutrophils to the lung. Our result clearly demonstrates that F. novicida-infected amoebae are not infectious particles in a murine model of tularemia.

F. novicida; amoeba; mice

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