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Open AccessArticle

Increased Sensitivity of Amoeba-Grown Francisella Species to Disinfectants

Department of Microbiology and Parasitology, University of Rijeka, Faculty of Medicine, 51000 Rijeka, Croatia
Department of Histology and Embryology, Faculty of Medicine, University of Zagreb, 10000 Zagreb, Croatia
Department of Microbiology and Immunology, College of Medicine, University of Louisville, Louisville, KY 40202, USA
Center for Predictive Medicine, College of Medicine, University of Louisville, Louisville, KY 40202, USA
Author to whom correspondence should be addressed.
Microorganisms 2020, 8(9), 1260;
Received: 21 July 2020 / Revised: 11 August 2020 / Accepted: 18 August 2020 / Published: 20 August 2020
(This article belongs to the Special Issue Tularemia: Pathogenesis, Diagnostic, Prevention, and Treatment)
Francisella tularensis is a highly infectious, intracellular bacterium and it is the causative agent of tularemia. The bacterium has been isolated from more than 250 species, including protozoa. Previous studies have shown that the growth of Legionella pneumophila within the amoeba results in a dramatic increase in the resistance to disinfectants. Since Francisella persists in the environment for years, this study investigates whether Acanthamoeba castellanii-grown F. novicida exhibits an alteration in the resistance to disinfectants. The disinfectants used are didecyldimethylammonium chloride (DDAC) combined with isopropyl alcohol (D1), benzalkonium chloride combined with DDAC and formic acid (D2), and polyhexamethylene biguanide (PHMB, D3). The effect of disinfectants on the bacterial viability is determined by a colony-forming unit (CFU), by transmission electron microscopy (TEM), by fluorescence microscopy, and the damage of the bacterial membrane. Our data has shown that only a one-log10 loss in bacterial viability is exhibited upon treatment of agar-grown Francisella, while in amoeba-grown Francisella there was a three-log10 difference with D3. The D1 disinfectant sterilized the bacteria within 10 s. The treatment of agar-grown F. novicida with D2 reduces bacterial viability by seven-log10 within 10 s and 15 min, respectively. Surprisingly, the treatment of amoeba-grown F. novicida with D2 results in a total loss of bacterial viability. In conclusion, A. castellanii-grown F. novicida is more susceptible to many disinfectants. View Full-Text
Keywords: Acanthamoeba; Francisella; disinfectant; sensitivity Acanthamoeba; Francisella; disinfectant; sensitivity
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MDPI and ACS Style

Knežević, M.; Marečić, V.; Ožanič, M.; Špoljarić, N.; Kelava, I.; Ćurlin, M.; Kwaik, Y.A.; Mihelčić, M.; Šantić, M. Increased Sensitivity of Amoeba-Grown Francisella Species to Disinfectants. Microorganisms 2020, 8, 1260.

AMA Style

Knežević M, Marečić V, Ožanič M, Špoljarić N, Kelava I, Ćurlin M, Kwaik YA, Mihelčić M, Šantić M. Increased Sensitivity of Amoeba-Grown Francisella Species to Disinfectants. Microorganisms. 2020; 8(9):1260.

Chicago/Turabian Style

Knežević, Maša; Marečić, Valentina; Ožanič, Mateja; Špoljarić, Nikolina; Kelava, Ina; Ćurlin, Marija; Kwaik, Yousef A.; Mihelčić, Mirna; Šantić, Marina. 2020. "Increased Sensitivity of Amoeba-Grown Francisella Species to Disinfectants" Microorganisms 8, no. 9: 1260.

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