Valentina Marečić

University of Rijeka

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MŠ

Marina Šantić

University of Rijeka

Mateja Ožanić

University of Rijeka

Mirna Mihelčić

University of Rijeka

Ina Kelava

University of Rijeka

Yousef Abu Kwaik

University of Louisville

Maša Knežević

University of Rijeka

Olga Shevchuk

Essen University Hospital

Anders Sjöstedt

Umeå University

Michael Steinert

Technische Universität Braunschweig

MĆ

Marija Ćurlin

Catholic University of Croatia

Cooperative Institutions

University of Rijeka

Umeå University

University of Defence

University of Zagreb

University Hospital for Infectious Diseases "Dr Fran Mihaljevic"

Swedish Defence Research Agency

University of Defence

Croatian Veterinary Institute

University of Würzburg

Military Medical Academy

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Survival of Francisella novicida after exposure to drying and different growth conditions

Corina Kukurin Dario Matulja Ana Mihatović Mateja Ožanić Valentina Marečić

Francisella

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Evaluation of effectiveness of chemical disinfectants on the growth of Francisella novicida-growing amoebae

Nikolina Špoljarić Valentina Marečić Mateja Ožanić Marina Šantić

Francisella tularensis is a highly infectious, gram-negative intracellular bacterium and the causative agent of tularemia. The bacteria has been isolated from more than 250 wild species including protozoa cells. Our previous study have shown that infection of amoebae by F. novicida, surprisingly, did not enhance the infectivity of Francisella. Since the organisms is very virulent and persists in the environment for years it is important to determine the efficacy of disinfectants, when used to inactivate this biological agent. Our previous results have shown that disinfectants, 5 % of Asepsol has bactericide effect on F. novicida while 0.2% Bigvasan and 1% Descocid only reduce the number of bacterial colonies. In this study, we further investigated the effectiveness of three disinfectants (0.2%, 0.5% and 1.0% Bigvasan and Descocid as well as 1%, 2% and 5% Asepsol eko) on decontamination of F. novicida after growing of the bacterium in Acanthamoeba castellanii for 48 hours. Our results showed that Asepsol (1%, 2% and 5%) and 1% Descocid completely inhibited bacterial growth, regardless the time of exposure (10 sec, 5, 10 and 15 minutes). The efficacy of Bigvasan and Descocid was concentration and time of the exposure dependent, on the Francisella-growing amoebae. Surprisingly, in comparison to previous results, F. novicida in growing amoebae are more sensitive to decontamination by 1% of Descocid and 0.2 % of Bigvasan. We can conclude that among tested disinfectants, Asepsol eko, even at four time’s lower concentrations than manufacturer-recommended, exhibits the best bactericidal activity against F. novicida-growing amoeba.

Francisella

Tularemia

Disinfectant

Naegleria fowleri

Infectivity

Human decontamination

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Intracellular life of Francisella and Legionella within amoebae cells

Medicina : glasilo Hrvatskoga liječničkoga zbora, Podružnica Rijeka (2016)

Mateja Ožanić Valentina Marečić Ivana Gobin Marina Šantić

Free-living amoebae are present in the nature, feeding mainly with bacteria, fungi, and algae. Some microorganisms have evolved different mechanisms to resist the digestion by amoebae and they are called “amoeba-resistant microorganisms”. Some of the important human bacterial pathogens belong to this category including Cryptococcus neoformans, Chlamydophila pneumoniae, Mycobacterium avium, Listeria monocytogenes, Pseudomonas aeruginosa, Legionella spp., and Francisella tularensis. Francisella and Legionella are gram negative facultative intracellular bacteria. Although the diseases they cause are completely different, they share some of the unique features in intracellular lifestyle within amoeba cells.

Francisella

Legionella

Intracellular parasite

Fastidious organism

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Dictyostelium discoideum kao modelni organizam za proučavanje unutarstaničnog života Francisella novicida

Ina Kelava Valerija Nora Mateja Ožanić Valentina Marečić Marina Šantić

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Prevalence of Francisella tularensis among small rodents in continental Croatia

Mirna Mihelčić Josipa Habuš Marko Vucelja Valentina Marečić Petra Svoboda

Tularemia

Francisella

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The autophagy plays an important role in intracellular life of Francisella within Dictyostelium cells.

Mateja Ožanić Valerija Nora Valentina Marečić Mihelčić Marina Šantić

Autophagy or autophagocytosis is an evolutionally preserved catabolic process that involves the degradation of cytoplasmic components. During infection, various microorganisms regulate the autophagy process differently. Studies have shown that F. novicida in some cells stimulate autophagy, and in others suppress the autophagy process in favor of intracellular replication. Most of the studies were performed in mammalian cells, and very little is known about the autophagy process in the amoeba cell after infection with Francisella. It has been shown that in Dictyostelium, F. noatunensis subsp. noatunensis interacts with the autophagic machinery. There are no data about the role of autophagy of survival and replication of F. novicida and F. tularensis subsp. holarctica in Dictyostelium discoideum. In this study, we monitored the autophagy process in this social amoeba using different inducers and inhibitors of autophagy over infection with F. novicida and F. tularensis subsp. holarctica. The results have shown that treatment of cells with autophagy inhibitors, chloroquine and wortmannin has a negative effect on survival, replication and intracellular trafficking of both strains of Francisella. In contrast, induction of autophagy in amoebae cells results of high number of intracellular bacteria, successful replication in Francisella containing vacuole. We can conclude that the formation of an autophagic vacuole support the intracellular lifestyle of Francisella within Dictyostelium discoideum.

Intracellular parasite

Francisella

ATG8

BAG3

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Intracellular trafficking of Francisella tularensis subsp. novicida within Dictyostelium discoideum

Valentina Marečić Mateja Ožanić Olga Shevchuk Michael Steinert Marina Šantić

Francisella

Intracellular parasite

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Isolation of F. novicida-Containing Phagosome from Infected Human Monocyte Derived Macrophages

Frontiers in Cellular and Infection Microbiology (2017)

Valentina Marečić Olga Shevchuk Mateja Ožanić Mirna Mihelčić Michael Steinert

Francisella is a gram-negative bacterial pathogen, which causes tularemia in humans and animals. A crucial step of Francisella infection is its invasion of macrophage cells. Biogenesis of the Francisella-containing phagosome (FCP) is arrested for ~15 minutes at the endosomal stage, followed by gradual bacterial escape into the cytosol, where the microbe proliferates. The crucial step in pathogenesis of tularemia is short and transient presence of the bacterium within phagosome. Isolation of FCPs for further studies has been challenging due to the short period of time of bacterial residence in it and the characteristics of the FCP. Here, we will for the first time present the method for isolation of the FCPs from infected human monocytes-derived macrophages (hMDMs). For elimination of lysosomal compartment these organelles were pre-loaded with dextran coated colloidal iron particles prior infection and eliminated by magnetic separation of the post-nuclear supernatant (PNS). We encountered the challenge that mitochondria has similar density to the FCP. To separate the FCP in the PNS from mitochondria, we utilized iodophenylnitrophenyltetrazolium, which is converted by the mitochondrial succinate dehydrogenase into formazan, leading to increased density of the mitochondria and allowing separation by the discontinuous sucrose density gradient ultracentrifugation. The purity of the FCP preparation and its acquisition of early endosomal markers was confirmed by Western blots, confocal and transmission electron microscopy. Our strategy to isolate highly pure FCPs from macrophages should facilitate studies on the FCP and its biogenesis.

Francisella

Organelle

10.3389/fcimb.2017.00303

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Intracellular trafficking of pilo mutant within human macrophages and pathogenesis of tularemia in BALB/c mice

Mateja Ožanić Valentina Marečić Yousef Abu Kwaik Marina Šantić

Tularemia

Pathogenesis

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Epidemiologic and Epizootic Data of Tularemia in the Past and in the Recent History in Croatia

Microorganisms (2020)

Mirna Mihelčić Valentina Marečić Mateja Ožanić Ina Kelava Maša Knežević

Tularemia is a zoonotic disease caused by Francisella tularensis. A large number of recent studies have provided an update on the disease characteristics and the distribution across Europe. In Croatia, most of the clinical cases, as well as the reports of the disease in animals, date from the 20th century. In that period, epidemic and epizootic research had given detailed information about endemic regions and their characteristics, including suspected animal hosts and vectors. The region along the middle course of the Sava River, called Middle Posavina, is described as an endemic region, i.e., a "natural focus" of tularemia, in Croatia. In the 21st century, cases of human tularemia are being reported sporadically, with ulceloglandular, oropharyngeal and typhoid forms of disease. A majority of the described cases are linked with the consumption of contaminated food or water. The disease outbreaks still occur in areas along the course of the river Sava and in northwest Croatia. In this review article, we have summarized epidemiologic and epizootic data of tularemia in the past and in recent Croatian history.

Tularemia

Epizootic

Zoonotic disease

10.3390/microorganisms8050721

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