The Experts below are selected from a list of 21219 Experts worldwide ranked by ideXlab platform
Anders Sjostedt - One of the best experts on this subject based on the ideXlab platform.
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An In Vitro Co-culture Mouse Model Demonstrates Efficient Vaccine-Mediated Control of Francisella tularensis SCHU S4 and Identifies Nitric Oxide as a Predictor of Efficacy
Frontiers in cellular and infection microbiology, 2016Co-Authors: Igor Golovliov, Helena Lindgren, Wayne Conlan, Kjell Eneslätt, Amandine Mosnier, Thomas Henry, Anders SjostedtAbstract:Francisella tularensis is a highly virulent Intracellular Bacterium and cell-mediated immunity is critical for protection, but mechanisms of protection against highly virulent variants, such as the ...
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Roles of Reactive Oxygen Species-Degrading Enzymes of Francisella tularensis SCHU S4
Infection and immunity, 2015Co-Authors: Johan Binesse, Helena Lindgren, Lena Lindgren, Wayne Conlan, Anders SjostedtAbstract:Francisella tularensis is a facultative Intracellular Bacterium utilizing macrophages as its primary Intracellular habitat and is therefore highly capable of resisting the effects of reactive oxyge ...
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Intracellular survival mechanisms of Francisella tularensis, a stealth pathogen
Microbes and infection, 2005Co-Authors: Anders SjostedtAbstract:Research on the highly virulent and contagious, facultative Intracellular Bacterium Francisella tularensis has come into the limelight recently, but still little is known regarding its virulence mechanisms. This review summarizes recent studies on its intramacrophage survival mechanisms, some of which appear to be novel.
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Distinct roles of reactive nitrogen and oxygen species to control infection with the facultative Intracellular Bacterium Francisella tularensis.
Infection and immunity, 2004Co-Authors: Helena Lindgren, Stephan Stenmark, Wangxue Chen, Arne Tärnvik, Anders SjostedtAbstract:Reactive nitrogen species (RNS) and reactive oxygen species (ROS) are important mediators of the bactericidal host response. We investigated the contribution of these two mediators to the control of infection with the facultative Intracellular Bacterium Francisella tularensis. When intradermally infected with the live vaccine strain F. tularensis LVS, mice deficient in production of RNS (iNOS(-/-) mice) or in production of ROS by the phagocyte oxidase (p47(phox-/-) mice) showed compromised resistance to infection. The 50% lethal dose (LD(50)) for iNOS(-/-) mice was 500,000 CFU for wild-type mice. The iNOS(-/-) mice survived for 26.4 +/- 1.8 days, and the p47(phox-/-) mice survived for 10.1 +/- 1.3 days. During the course of infection, the serum levels of gamma interferon (IFN-gamma) and interleukin-6 were higher in iNOS(-/-) and p47(phox-/-) mice than in wild-type mice. Histological examination of livers of iNOS(-/-) mice revealed severe liver pathology. Splenocytes obtained 5 weeks after primary infection from antibiotic-treated iNOS(-/-) mice showed an in vitro recall response that was similar in magnitude and greater secretion of IFN-gamma compared to cells obtained from wild-type mice. In summary, mice lacking expression of RNS or ROS showed extreme susceptibility to infection with F. tularensis LVS. The roles of RNS and ROS seemed to be distinct since mice deficient in production of ROS showed dissemination of infection and died during the early phase of infection, whereas RNS deficiency led to severe liver pathology and a contracted course of infection.
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an attenuated strain of the facultative Intracellular Bacterium francisella tularensis can escape the phagosome of monocytic cells
Infection and Immunity, 2003Co-Authors: Igor Golovliov, Vladimir Baranov, Zuzana Krocova, Hana Kovarova, Anders SjostedtAbstract:The facultative Intracellular Bacterium Francisella tularensis is a highly virulent and contagious organism, and little is known about its Intracellular survival mechanisms. We studied the Intracellular localization of the attenuated human vaccine strain, F. tularensis LVS, in adherent mouse peritoneal cells, in mouse macrophage-like cell line J774A.1, and in human macrophage cell line THP-1. Confocal microscopy of infected J774A.1 cells indicated that during the first hour of infection the bacteria colocalized with the late endosomal-lysosomal glycoprotein LAMP-1, but within 3 h this colocalization decreased significantly from approximately 60% to 30%. Transmission electron microscopy revealed that >90% of bacteria were not enclosed by a phagosomal membrane after 2 h of infection, and some bacteria were in vacuoles that were only partially surrounded by a limiting membrane. Similar findings were obtained with all three host cell types. Immunoelectron microscopy performed with an F. tularensis LVS-specific polyclonal rabbit antiserum showed that the antiserum stained a thick, evenly distributed capsule-like material in bacteria grown in broth. In contrast, Intracellular F. tularensis LVS cells were only marginally stained with this antiserum. Instead, most of the immunoreactive material was diffusely localized in the phagosomes or was associated with the phagosomal membrane. Our findings indicate that F. tularensis LVS is able to escape from the phagosomes of macrophages via a mechanism that may involve degradation of the phagosomal membrane.
Karen D. Mccoy - One of the best experts on this subject based on the ideXlab platform.
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Diversity and global distribution of the Coxiella Intracellular Bacterium in seabird ticks.
Ticks and tick-borne diseases, 2014Co-Authors: Olivier Duron, Elsa Jourdain, Karen D. MccoyAbstract:The obligate Intracellular Bacterium Coxiella burnetii is the etiological agent of Q fever, a widespread zoonotic disease whose most common animal reservoirs are domestic ruminants. Recently, a variety of Coxiella-like organisms have also been reported from non-mammalian hosts, including pathogenic forms in birds and forms without known effects in ticks, raising questions about the potential importance of non-mammalian hosts as reservoirs of Coxiella in the wild. In the present study, we examined the potential role of globally-distributed seabird ticks as reservoirs of these bacteria. To this aim, we tested for Coxiella infection 11 geographically distinct populations of two tick species frequently found in seabird breeding colonies, the hard tick Ixodes uriae (Ixodidae) and soft ticks of the Ornithodoros (Carios) capensis group (Argasidae). We found Coxiella-like organisms in all O. capensis sensu lato specimens, but only in a few I. uriae specimens of one population. The sequencing of 16S rDNA and GroEL gene sequences further revealed an unexpected Coxiella diversity, with seven genetically distinct Coxiella-like organisms present in seabird tick populations. Phylogenetic analyses show that these Coxiella-like organisms originate from three divergent subclades within the Coxiella genus and that none of the Coxiella strains found in seabird ticks are genetically identical to the forms known to be associated with pathogenicity in vertebrates, including C. burnetii. Using this data set, we discuss the potential epidemiological significance of the presence of Coxiella in seabird ticks. Notably, we suggest that these organisms may not be pathogenic forms, but rather behave as endosymbionts engaged in intricate interactions with their tick hosts.
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Diversity and global distribution of the Coxiella Intracellular Bacterium in seabird ticks
Ticks and Tick-borne Diseases, 2014Co-Authors: Olivier Duron, Elsa Jourdain, Karen D. MccoyAbstract:The obligate Intracellular Bacterium Coxiella burnetii is the etiological agent of Q fever, a widespread zoonotic disease whose most common animal reservoirs are domestic ruminants. Recently, a variety of Coxiella-like organisms have also been reported from non-mammalian hosts, including pathogenic forms in birds and forms without known effects in ticks, raising questions about the potential importance of non-mammalian hosts as reservoirs of Coxiella in the wild. In the present study, we examined the potential role of globally-distributed seabird ticks as reservoirs of these bacteria. To this aim, we tested for Coxiella infection 11 geographically distinct populations of two tick species frequently found in seabird breeding colonies, the hard tick Ixodes uriae (Ixodidae) and soft ticks of the Ornithodoros (Carios) capensis group (Argasidae). We found Coxiella-like organisms in all O. capensis sensu lato specimens, but only in a few I. uriae specimens of one population. The sequencing of 16S rDNA and GroEL gene sequences further revealed an unexpected Coxiella diversity, with seven genetically distinct Coxiella-like organisms present in seabird tick populations. Phylogenetic analyses show that these Coxiella-like organisms originate from three divergent subclades within the Coxiella genus and that none of the Coxiella strains found in seabird ticks are genetically identical to the forms known to be associated with pathogenicity in vertebrates, including C burnetii. Using this data set, we discuss the potential epidemiological significance of the presence of Coxiella in seabird ticks. Notably, we suggest that these organisms may not be pathogenic forms, but rather behave as endosymbionts engaged in intricate interactions with their tick hosts. (C) 2014 Elsevier GmbH. All rights reserved.
Abdu F. Azad - One of the best experts on this subject based on the ideXlab platform.
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Current Protocols in Microbiology - Laboratory Maintenance of Rickettsia rickettsii
Current Protocols in Microbiology, 2008Co-Authors: Nicole C. Ammerman, Magda Beier-sexton, Abdu F. AzadAbstract:This unit includes protocols for the laboratory maintenance of the obligate Intracellular Bacterium Rickettsia rickettsii, including propagation in mammalian cell cultures, as well as isolation, counting, and storage procedures. Regulations for working with R. rickettsii in biosafety level 3 containment are also discussed.
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Laboratory maintenance of Rickettsia rickettsii.
Current protocols in microbiology, 2008Co-Authors: Nicole C. Ammerman, Magda Beier-sexton, Abdu F. AzadAbstract:This unit includes protocols for the laboratory maintenance of the obligate Intracellular Bacterium Rickettsia rickettsii, including propagation in mammalian cell cultures, as well as isolation, counting, and storage procedures. Regulations for working with R. rickettsii in biosafety level 3 containment are also discussed.
Ann M. Fallon - One of the best experts on this subject based on the ideXlab platform.
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Conditions facilitating infection of mosquito cell lines with Wolbachia, an obligate Intracellular Bacterium.
In vitro cellular & developmental biology. Animal, 2019Co-Authors: Ann M. FallonAbstract:Factors that influence establishment of Wolbachia, an obligate Intracellular Bacterium, in novel insect hosts or uninfected insect cell lines are poorly understood. Infectivity of Wolbachia strain wStr was correlated with flow cytometric profiles to define optimal conditions for harvesting an infectious inoculum. Wolbachia recovered from the cell culture supernatant after gentle pipetting of infected cells represented about 1% of the total bacterial population and were more infectious than Wolbachia that remained associated with intact cells and/or membranes after low-speed centrifugation. Optimal establishment of a robust infection in naive cells required 6 d, at a ratio of 80 to 160 bacteria per cell. Among Aedes albopictus mosquito cell lines, an aneuploid line with a 4n + 1 karyotype was more susceptible to infection than diploid lines. These findings contribute to the in vitro manipulation of Wolbachia, illustrate some of the many factors that influence infectivity, and identify areas for future investigation.
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Flow cytometric evaluation of the Intracellular Bacterium, Wolbachia pipientis, in mosquito cells
Journal of microbiological methods, 2014Co-Authors: Ann M. FallonAbstract:Conditions for flow cytometric evaluation of the Intracellular Bacterium, Wolbachia pipientis, in infected mosquito cells are described. This approach will streamline investigation of Wolbachia's interactions with host cells and facilitate identification of culture conditions that select for Wolbachia-infected cells.
C Bandi - One of the best experts on this subject based on the ideXlab platform.
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Taxonomic status of the Intracellular Bacterium Wolbachia pipientis.
International journal of systematic and evolutionary microbiology, 2007Co-Authors: C Paraskevopoulos, K Bourtzis, S L O'neill, J H Werren, S R Bordenstein, C BandiAbstract:Wolbachia pipientis is a maternally inherited, Intracellular Bacterium found in more than 20 % of all insects, as well as numerous other arthropods and filarial nematodes. It has been the subject of a growing number of studies in recent decades, because of the remarkable effects it has on its arthropod hosts, its potential as a tool for biological control of arthropods of agricultural and medical importance and its use as a target for treatment of filariasis. W. pipientis was originally discovered in cells of the mosquito Culex pipiens and is the only formally described member of the genus. Molecular sequence-based studies have revealed a number of phylogenetically diverse strains of W. pipientis. Owing to uncertainty about whether W. pipientis comprises more than one species, researchers in the field now commonly refer to W. pipientis simply as Wolbachia. In this note, we briefly review higher-level phylogenetic and recombination studies of W. pipientis and propose that all the Intracellular symbionts known to cluster closely with the type strain of W. pipientis, including those in the currently recognized supergroups (A-H), are officially given this name.
