Enhanced survival but not amplification of Francisella spp. in the presence of free-living amoebae

Buse, Helen Y. and Schaefer III, Frank W. and Rice, Eugene W. (2016) Enhanced survival but not amplification of Francisella spp. in the presence of free-living amoebae. Acta Microbiologica et Immunologica Hungarica, 64 (1). pp. 17-36. ISSN 1217-8950


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Transmission of Francisella tularensis, the etiologic agent of tularemia, has been associated with various water sources. Survival of many waterborne pathogens within free-living amoeba (FLA) is well documented; however, the role of amoebae in the environmental persistence of F. tularensis is unclear. In this study, axenic FLA cultures of Acanthamoeba castellanii, Acanthamoeba polyphaga, and Vermamoeba vermiformis were each inoculated with virulent strains of F. tularensis (Types A and B), the attenuated live vaccine strain, and Francisella novicida. Experimental parameters included low and high multiplicity of infection and incubation temperatures of 25 and 30 °C for 0–10 days. Francisella spp. survival was enhanced by the presence of FLA; however, bacterial growth and protozoa infectivity were not observed. In contrast, co-infections of A. polyphaga and Legionella pneumophila, used as an amoeba pathogen control, resulted in bacterial proliferation, cytopathic effects, and amoebal lysis. Collectively, even though short-term incubation with FLA was beneficial, the long-term effects on Francisella survival are unknown, especially given the expenditure of available amoebal derived nutrients and the fastidious nature of Francisella spp. These factors have clear implications for the role of FLA in Francisella environmental persistence.

Item Type: Article
Subjects: Q Science / természettudomány > QR Microbiology / mikrobiológia
Depositing User: Ágnes Sallai
Date Deposited: 03 Apr 2017 08:15
Last Modified: 30 Nov 2017 00:15

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