engleski

Intracellular survival of Francisella tularensis in Acanthamoeba spp.

Francisella tularensis is a gram-negative facultative intracellular bacterium that can cause a fatal disease, tularemia, in human and animals. This organism has been isolated from over 250 wildlife species, including fish, birds, amphibians, rabbits, squirrels, hares, voles, ticks, and flies. It resists harsh environments, and has been shown to survive in water and mud for more than a year. The natural reservoirs in water are protozoa including many species of amoeba. Pathogenic Acanthamoeba are known to infect the CNS, resulting in fatal granulomatous encephalitis. The mechanisms associated with the pathogenesis remain unclear as well as the symptoms of the disease in combination with F. tularensis infections. Previous results have shown survival and growth of F. tularensis LVS strain in Acanthamoeba palestinensis. There are no evidence of intracellular survival and growth of F. tularensis subsp. novicida in Acanthamoeba spp. In addition, the role of iglD and iglC genes of Francisella tularensis in Acanthamoeba survival and growth are unknown. Our results showed that F. tularensis survive and replicates in Acanthamoeba spp. with the peak of replication at 24 h post infection. In contrast, the iglD and iglC mutant strains of F. tularensis subsp. novicida were completely defective in intrcelullural replication, and cleared from the Acanthamoeba cells within 12 h post infection. We can conclude that F. tularensis subsp. novicida is also connected with natural water system and that Acanthamoeba spp. plays an important role in survival of the bacteria in nature. For the first time we showed that iglD and iglC genes of F. tularensis subsp. novicida are crucial for their survival and intracellular replication in Acanthamoeba spp.

Francisella; Acanthamoeba; survival

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