Abstract
Francisella tularensis is a facultative intracellular bacterium that causes tularemia in humans and animals. Epidemiology of tularemia worldwide is often associated with water-borne transmission, which includes mosquitoes and amoebae as the potential host reservoirs of the bacteria in water environment. In vitro studies showed intracellular replication of F. tularensis within Acanthamoeba castellanii and Hartmanella vermiformis cells. While infection of amoeba by Legionella pneumophila has been shown to enhance infectivity of L. pneumophila the role of F. tularensis-infected protozoa in the pathogenesis of tularemia is not known. We used 6 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 or with F. novicida-infected A. castellanii. Surprisingly, infection with F. novicida-infected A. castellanii did not lead to bronchopneumonia in Balb/c mice, and Francisella did not disseminate into the liver and spleen. 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 numbers of neutrophils in the lungs of Balb/c mice were significantly lower in the infection of mice with F. novicida-infected A. castellanii in comparison to group of mice infected only with F. novicida. These results demonstrate that following inoculation of mice with F. novicida-infected A. castellanii, mice did not develop tularemia.
Highlights
Francisella tularensis is a gram negative bacterium and causative agent of zoonotic disease, tularemia
A/J mice were inoculated with L. pneumophila (105 cfu per mouse) and/or L. pneumophila-infected A. castellanii (MOI 10, 106 amoebae containing 105 bacteria, harvested after 6 h of coculture)
Our and other studies have shown that F. tularensis subsp. holarctica, tularensis, and F. novicida survive and replicate in A. castellanii while F. novicida is able to replicate in H. vermiformis as well (Abd et al, 2003; El-Etr et al, 2009; Santic et al, 2011)
Summary
Francisella tularensis is a gram negative bacterium and causative agent of zoonotic disease, tularemia. Five species of the genus Francisella has been recognized: F. tularensis, F. philomiragia, F. hispaniensis, F. noatunensis, and F. novicida (Sjödin et al, 2012; Kingry and Petersen, 2014). Tularemia in humans is mostly caused by two subspecies of F. tularensis, tularensis (Type A) and holarctica (Type B). F. novicida U112 is avirulent in immunocompetent humans but is very virulent in experimental mice, only few bacteria cause disease and death, similar to Francisella tularensis subsp. Tularensis (Sjödin et al, 2012). The most common way of transmission of the disease is by exposure to infected arthropod vectors, or by handling, ingesting, or inhaling infectious materials.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
