Rickettsia conorii

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Didier Raoult - One of the best experts on this subject based on the ideXlab platform.

  • Rickettsia conorii is a potent complement activator in vivo and combined inhibition of complement and cd14 is required for attenuation of the cytokine response ex vivo
    Clinical Microbiology and Infection, 2016
    Co-Authors: Kari Otterdal, Didier Raoult, Aranzazu Portillo, Elisabeth Astrup, Judith K Ludviksen, Camilla Schjalm, Juan P Olano, Bente Halvorsen
    Abstract:

    Mediterranean spotted fever caused by Rickettsia conorii is a potentially lethal disease characterized by vascular inflammation affecting multiple organs. Studies of R. conorii so far have focused on activation of inflammatory cells and their release of inflammatory cytokines, but complement activation has not been investigated in R. conorii-infected patients. Here, we performed a comprehensive analysis of complement activation markers and the soluble cross-talking co-receptor CD14 (sCD14) in plasma from R. conorii-infected patients. The clinical data were supplemented with ex vivo experiments where the cytokine response was characterized in human whole blood stimulated with R. conorii. Complement activation markers at the level of C3 (C3bc, C3bBbP) and terminal pathway activation (sC5b-9), as well as sCD14, were markedly elevated (p <0.01 for all), and closely correlated (p <0.05 for all), in patients at admission compared with healthy matched controls. All tested markers were significantly reduced to baseline values at time of follow up. Rickettsia conorii incubated in human whole blood was shown to trigger complement activation accompanied by release of the inflammatory cytokines interleukin-1β (IL-1β), IL-6, IL-8 and tumour necrosis factor. Whereas inhibition of either C3 or CD14 had only a minor effect on released cytokines, combined inhibition of C3 and CD14 resulted in significant reduction, virtually to baseline levels, of the four cytokines (p <0.05 for all). Our data show that complement is markedly activated upon R. conorii infection and complement activation is, together with CD14, responsible for a major part of the cytokine response induced by R. conorii in human whole blood.

  • Rickettsia conorii israelensis in rhipicephalus sanguineus ticks sardinia italy
    Ticks and Tick-borne Diseases, 2014
    Co-Authors: Valentina Chisu, Didier Raoult, Cristina Socolovschi, Giovanna Masala, Cipriano Foxi, Philippe Parola
    Abstract:

    The presence of tick-borne Rickettsia spp. was examined by PCR using DNA samples extracted from 254 ticks collected from mammals originating from northern and eastern Sardinia, Italy. The spotted fever group Rickettsial agent Rickettsia conorii israelensis was detected in 3 Rhipicephalus sanguineus ticks from a dog for the first time in this geographical area. In addition, Ri. massiliae, Ri. slovaca, and Ri. aeschlimannii were detected in Rh. turanicus, Rh. sanguineus, Dermacentor marginatus, and Hyalomma marginatum marginatum ticks from dogs, goats, wild boar, and horse. Moreover, Candidatus Rickettsia barbariae was detected in 2 Rh. turanicus ticks from goats. The detection of Ri. conorii israelensis, an emergent agent which causes Israeli spotted fever, increases our knowledge on tick-borne rickettsioses in Sardinia.

  • genome sequence of Rickettsia conorii subsp israelensis the agent of israeli spotted fever
    Journal of Bacteriology, 2012
    Co-Authors: Erwin Sentausa, Didier Raoult, Khalid El Karkouri, Catherine Robert, Pierreedouard Fournier
    Abstract:

    Rickettsia conorii subsp. israelensis is the agent of Israeli spotted fever. The present study reports the draft genome of Rickettsia conorii subsp. israelensis strain ISTT CDC1, isolated from a Rhipicephalus sanguineus tick collected in Israel.

  • genome sequence of Rickettsia conorii subsp caspia the agent of astrakhan fever
    Journal of Bacteriology, 2012
    Co-Authors: Erwin Sentausa, Didier Raoult, Khalid El Karkouri, Catherine Robert, Pierreedouard Fournier
    Abstract:

    Rickettsia conorii subsp. caspia is the agent of Astrakhan fever, a spotted fever group rickettsiosis endemic to Astrakhan, Russia. The present study reports the draft genome of Rickettsia conorii subsp. caspia strain A-167.

  • why are there so few Rickettsia conorii conorii infected rhipicephalus sanguineus ticks in the wild
    PLOS Neglected Tropical Diseases, 2012
    Co-Authors: Cristina Socolovschi, Didier Raoult, Jean Gaudart, Idir Bitam, Thi Phong Huynh, Philippe Parola
    Abstract:

    Background: Rickettsia conorii conorii is the etiological agent of Mediterranean spotted fever, which is transmitted by the brown dog tick, Rhipicephalus sanguineus. The relationship between the Rickettsia and its tick vector are still poorly understood one century after the first description of this disease.

Pierreedouard Fournier - One of the best experts on this subject based on the ideXlab platform.

  • genome sequence of Rickettsia conorii subsp israelensis the agent of israeli spotted fever
    Journal of Bacteriology, 2012
    Co-Authors: Erwin Sentausa, Didier Raoult, Khalid El Karkouri, Catherine Robert, Pierreedouard Fournier
    Abstract:

    Rickettsia conorii subsp. israelensis is the agent of Israeli spotted fever. The present study reports the draft genome of Rickettsia conorii subsp. israelensis strain ISTT CDC1, isolated from a Rhipicephalus sanguineus tick collected in Israel.

  • genome sequence of Rickettsia conorii subsp caspia the agent of astrakhan fever
    Journal of Bacteriology, 2012
    Co-Authors: Erwin Sentausa, Didier Raoult, Khalid El Karkouri, Catherine Robert, Pierreedouard Fournier
    Abstract:

    Rickettsia conorii subsp. caspia is the agent of Astrakhan fever, a spotted fever group rickettsiosis endemic to Astrakhan, Russia. The present study reports the draft genome of Rickettsia conorii subsp. caspia strain A-167.

  • genome sequence of Rickettsia conorii subsp indica the agent of indian tick typhus
    Journal of Bacteriology, 2012
    Co-Authors: Erwin Sentausa, Didier Raoult, Khalid El Karkouri, Catherine Robert, Pierreedouard Fournier
    Abstract:

    Rickettsia conorii subsp. indica is the agent of Indian tick typhus. The present study reports the draft genome of Rickettsia conorii subsp. indica strain ITTR (ATCC VR-597).

  • Kinetics of Antibody Responses in Rickettsia africae and Rickettsia conorii Infections
    Clinical and Vaccine Immunology, 2002
    Co-Authors: Pierreedouard Fournier, Mogens Jensenius, Herman Laferl, Sirka Vene, Didier Raoult
    Abstract:

    African tick-bite fever, caused by Rickettsia africae, is the most common tick-borne rickettsiosis in subSaharan Africa. Mediterranean spotted fever due to Rickettsia conorii also occurs in the region but is more prevalent in Mediterranean countries. Using microimmunofluorescence, we compared the development of immunoglobulin G (IgG) and IgM titers in 48 patients with African tick-bite fever and 48 patients with Mediterranean spotted fever. Doxycycline treatment within 7 days from the onset of disease significantly prevented the development of antibodies to R. africae. In patients with African tick-bite fever, the median times to seroconversion with IgG and IgM were 28 and 25 days, respectively, after the onset of symptoms. These were significantly longer by a median of 6 days for IgG and 9 days for IgM than the times for seroconversion in patients with Mediterranean spotted fever (P

  • kinetics of antibody responses in Rickettsia africae and Rickettsia conorii infections
    Clinical and Vaccine Immunology, 2002
    Co-Authors: Pierreedouard Fournier, Mogens Jensenius, Herman Laferl, Sirka Vene, Didier Raoult
    Abstract:

    African tick-bite fever, caused by Rickettsia africae, is the most common tick-borne rickettsiosis in subSaharan Africa. Mediterranean spotted fever due to Rickettsia conorii also occurs in the region but is more prevalent in Mediterranean countries. Using microimmunofluorescence, we compared the development of immunoglobulin G (IgG) and IgM titers in 48 patients with African tick-bite fever and 48 patients with Mediterranean spotted fever. Doxycycline treatment within 7 days from the onset of disease significantly prevented the development of antibodies to R. africae. In patients with African tick-bite fever, the median times to seroconversion with IgG and IgM were 28 and 25 days, respectively, after the onset of symptoms. These were significantly longer by a median of 6 days for IgG and 9 days for IgM than the times for seroconversion in patients with Mediterranean spotted fever (P <1 0 2 ). We recommend that sera collected 4 weeks after the onset of signs of patients with suspected African tick-bite fever should be used for the definitive serological diagnosis of R. africae infections. Rickettsia africae is the agent of African tick-bite fever, a tick-transmitted disease which was long mistaken for Mediterranean spotted fever caused by Rickettsia conorii. African tickbite fever is a common disease in sub-Saharan Africa (7), where it occurs in people in rural areas when they come into contact with Amblyomma spp., ticks of cattle and game (4). Two cases of African tick-bite fever have also been reported from Guadeloupe (French West Indies) (6). In contrast to Rhipicephalus ticks, which transmit R. conorii and are very host specific, Amblyomma ticks feed readily on people who may frequently become infested with large numbers of these ticks. Consequently, African tick-bite fever often occurs in groups of people and is characterized by multiple inoculation eschars (2, 7). Mediterranean spotted fever, however, most often occurs as sporadic cases and patients present with a single eschar. R. africae also causes only mild clinical signs, and frequently there is no rash. When a rash is present, it is vesicular in half the patients and maculopapulous in the other half (7). Currently, the routine laboratory diagnosis of these diseases is based on serology, in particular microimmunofluorescence (MIF). The test is, however, limited by serological cross-reactivity between the spotted fever group Rickettsiae and, at times, the test may not be able to identify the species causing an antibody response. Recently, we reported 119 cases of R. africae infection, the largest series to date, which enabled us to validate serological methods for the diagnosis of African tick-bite fever (7). We demonstrated that a specific diagnosis could be made when the immunoglobulin G (IgG) and IgM titers to R. africae were fourfold higher than against other species. Specific antibody responses could also be demonstrated by using Western blotting or cross-adsorption of sera. We describe here the antibody responses to R. africae in 48 patients with African tick-bite fever and compare these to those against R. conorii in 48 patients with Mediterranean spotted fever. In addition, we estimated the influence of early doxycycline therapy on the development of anti-R. africae antibodies.

Philippe Parola - One of the best experts on this subject based on the ideXlab platform.

  • Rickettsia conorii israelensis in rhipicephalus sanguineus ticks sardinia italy
    Ticks and Tick-borne Diseases, 2014
    Co-Authors: Valentina Chisu, Didier Raoult, Cristina Socolovschi, Giovanna Masala, Cipriano Foxi, Philippe Parola
    Abstract:

    The presence of tick-borne Rickettsia spp. was examined by PCR using DNA samples extracted from 254 ticks collected from mammals originating from northern and eastern Sardinia, Italy. The spotted fever group Rickettsial agent Rickettsia conorii israelensis was detected in 3 Rhipicephalus sanguineus ticks from a dog for the first time in this geographical area. In addition, Ri. massiliae, Ri. slovaca, and Ri. aeschlimannii were detected in Rh. turanicus, Rh. sanguineus, Dermacentor marginatus, and Hyalomma marginatum marginatum ticks from dogs, goats, wild boar, and horse. Moreover, Candidatus Rickettsia barbariae was detected in 2 Rh. turanicus ticks from goats. The detection of Ri. conorii israelensis, an emergent agent which causes Israeli spotted fever, increases our knowledge on tick-borne rickettsioses in Sardinia.

  • why are there so few Rickettsia conorii conorii infected rhipicephalus sanguineus ticks in the wild
    PLOS Neglected Tropical Diseases, 2012
    Co-Authors: Cristina Socolovschi, Didier Raoult, Jean Gaudart, Idir Bitam, Thi Phong Huynh, Philippe Parola
    Abstract:

    Background: Rickettsia conorii conorii is the etiological agent of Mediterranean spotted fever, which is transmitted by the brown dog tick, Rhipicephalus sanguineus. The relationship between the Rickettsia and its tick vector are still poorly understood one century after the first description of this disease.

  • experimental infection of rhipicephalus sanguineus with Rickettsia conorii conorii
    Clinical Microbiology and Infection, 2009
    Co-Authors: Cristina Socolovschi, Didier Raoult, K Matsumoto, P Brouqui, Philippe Parola
    Abstract:

    Little is known about the relationships between Rickettsia conorii conorii, the agent of Mediterranean spotted fever (MSF), and its main vector, the brown dog tick Rhipicephalus sanguineus [1]. Matsumoto et al. recently reported a high mortality of Rh. sanguineus group ticks infected with R. conorii conorii by several methods including the use of a bacteraemic rabbit [2]. It had been speculated that reasons for this reduction in fitness might include the geographic origin of the ticks, which came from Thailand where R. conorii conorii has not been reported, or was associated with the pathogen load acquired during laboratory experiments. Here we present complementary experiments to test these hypotheses.

  • transmission of Rickettsia conorii conorii in naturally infected rhipicephalus sanguineus
    Clinical Microbiology and Infection, 2009
    Co-Authors: Cristina Socolovschi, Didier Raoult, Idir Bitam, Philippe Parola
    Abstract:

    Rickettsia conorii conorii is the causative agent of Mediterranean spotted fever (MSF) a life-threatening zoonosis that is endemic in Mediterranean countries [1]. In the early 1930s, Olmer supposed that the vector of disease was the brown dog tick, Rhipicephalus sanguineus. In 1932, Blanc and Caminopetros demonstrated that larvae, nymphs, adults, and over winter unfed males and females could act as vectors of MSF [2]. It was also shown that when eggs or larvae obtained from infected Rh. sanguineus females, were crushed and used to inoculate humans, the patients contracted MSF. These data suggest that transovarial transmission of the MSF agent occurs in ticks. However, we are unaware of any well-documented demonstration of transovarial transmission rate of R. conorii in Rh. sanguineus (TOT, the proportion of infected females giving rise to at least one positive egg or larva), or the filial infection rate (FIR, proportion of infected eggs or larvae obtained from an infected female). Although it is not known, infection with R. conorii is maintained over several generations of Rh. sanguineus. Furthermore, a high mortality of Rh. sanguineus group ticks infected with R. conorii by several methods has been recently reported [3,4]. Our aim was to examine the vertical transmission of R. conorii in naturally infected Rh. sanguineus ticks, to establish a colony of infected ticks and to study the maintenance of infection through several generations. MATERIAL AND METHODS

  • transcriptional response of Rickettsia conorii exposed to temperature variation and stress starvation
    Research in Microbiology, 2005
    Co-Authors: Clarisse Rovery, Patricia Renesto, Philippe Parola, K Matsumoto, Hiroyuki Ogata, Nicolas Crapoulet, Didier Raoult
    Abstract:

    Rickettsia conorii is an obligate intracellular bacterium transmitted to humans by Rhipicephalus sanguineusticks. The success of this microorganism at surviving in nature implicates the ability to efficiently adapt to different environments, including the arthropod vector and the mammalian host. Numerous bacterial species possess a highly evolved system for stress adaptation. This so-called stringent response is mediated by guanosine 3 � ,5 � -bispyrophosphate and guanosine 3 � -diphosphate 5 � -triphosphate which are under spoT control in some Gramnegative bacteria. Interestingly, annotation of the R. conorii genome evidenced 5 spoT paralogs. We hypothesized that these spoT genes play a role in adaptation to environmental changes specifically encountered by Rickettsiae during their different life cycles. Transcription of the spoT paralogs was examined by RT-PCR from infected Vero cells maintained in rich or deficient culture media, from infected C6/36 insect cells cultured at various temperatures and from infected ticks. Our results demonstrated that the 5 spoT genes can be transcribed. SpoT1 (RC0374) is only transcribed upon stringent response. Transcription of spoT3 (RC0888) was never observed in arthropod cells or ticks, but was specific to R. conorii RNA extracted from infected Vero cells. These results indicate that Rickettsial spoT paralogs are independently transcribed, depending on the different infected hosts and the adaptive capacity of the pathogen. Bioinformatics analysis of these possibly encoded proteins is also reported.  2004 Elsevier SAS. All rights reserved.

Erwin Sentausa - One of the best experts on this subject based on the ideXlab platform.

Marina E Eremeeva - One of the best experts on this subject based on the ideXlab platform.

  • effects of Rickettsia conorii infection on the survival of rhipicephalus sanguineus ticks
    Clinical Microbiology and Infection, 2009
    Co-Authors: Michael L Levin, Marina E Eremeeva, Lindsay F Killmaster, Gregory A Dasch
    Abstract:

    Rickettsia conorii conorii is the aetiologic agent of boutonneuse fever, also known as Mediterranean spotted fever or Marseilles fever in the Mediterranean area where it is endemic. The brown dog tick, Rhipicephalus sanguineus, is recognised as the principal vector of R. conorii [1,2]. Although a few experimental studies have suggested transovarial and transstadial transmission of R. conorii in Rh. sanguineus [3], there are practically no data available on the efficiency of such transmission or on this vector–pathogen interaction. One recent publication evaluated several methods for infecting Rh. sanguineus with R. conorii, but reported high mortality in infected ticks [4], which may have resulted from incompatibility between the particular Rickettsial isolate and the source of ticks used, or from the manipulation itself. In an effort to establish a laboratory colony of Rh. sanguineus persistently infected with R. conorii for studying agent transmission, we assessed the effects of R. conorii infection on the survival of Rh. sanguineus larvae.

  • fatal Rickettsia conorii subsp israelensis infection israel
    Emerging Infectious Diseases, 2008
    Co-Authors: Miriam Weinberger, Avi Keysary, Judith Sandbank, Ronit Zaidenstein, Avi Itzhaki, Carmela Strenger, M Leitner, Christopher D Paddock, Marina E Eremeeva
    Abstract:

    Underdiagnosis of fatal spotted fever may be attributed to nonspecific clinical features and insensitive acute-phase serologic studies. We describe the importance of molecular and immunohistochemical methods in establishing the postmortem diagnosis of locally acquired Israeli spotted fever due to Rickettsia conorii subsp. israelensis in a traveler returning to Israel from India.

  • proposal to create subspecies of Rickettsia conorii based on multi locus sequence typing and an emended description of Rickettsia conorii
    BMC Microbiology, 2005
    Co-Authors: Marina E Eremeeva
    Abstract:

    Background Rickettsiae closely related to the Malish strain, the reference Rickettsia conorii strain, include Indian tick typhus Rickettsia (ITTR), Israeli spotted fever Rickettsia (ISFR), and Astrakhan fever Rickettsia (AFR). Although closely related genotypically, they are distinct serotypically. Using multilocus sequence typing (MLST), we have recently found that distinct serotypes may not always represent distinct species within the Rickettsia genus. We investigated the possibility of classifying Rickettsiae closely related to R. conorii as R. conorii subspecies as proposed by the ad hoc committee on reconciliation of approaches to bacterial systematics. For this, we first estimated their genotypic variability by using MLST including the sequencing of 5 genes, of 31 Rickettsial isolates closely related to R. conorii strain Malish, 1 ITTR isolate, 2 isolates and 3 tick amplicons of AFR, and 2 ISFR isolates. Then, we selected a representative of each MLST genotype and used multi-spacer typing (MST) and mouse serotyping to estimate their degree of taxonomic relatedness.

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