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Detection of Rickettsia species with seroreactivity to Rickettsia tillamookensis and Rickettsia rickettsii subsp. californica in domestic dogs in Northern California.

Rickettsia species phylotype G022 (G022) and Rickettsia tillamookensis both maintain a low infection prevalence in Ixodes pacificus ticks an … ned for antibodies against Rickettsia spp. and tested for seroreactivity against R. tillamookensis, Rickettsia rickettsii subsp. californica, and Rickettsia rhipicephali. Because G022 has not yet been isolated, this Rickettsia species was omitted from the serological survey. Of the 175 dogs tested, three (1.71%; 95% CI: 0.58%-4.90%) were seropositive for Rickettsia spp …

Experimental infection with Rickettsia rickettsii in an Amblyomma dubitatum tick colony, naturally infected by Rickettsia bellii.

Amblyomma dubitatum engorged females, naturally infected by Rickettsia bellii, were used to establish a laboratory colony. Larvae, nymphs, and adults were exposed to two strains of Rickettsia rickettsii by feeding on needle-inoculated guinea pigs, and thereafter reared on uninfected guinea pigs. After acquisition feeding, engorged larvae and nymphs molted to nymphs and adults, respectively, which were shown to be infected (confirming transstadial perpetuation), and were able to transmit both strains of R. rickettsii to uninfected animals, as demonstrated by clinical, serological, and molecular…

Biological properties of rabbit antibodies to a surface antigen of Rickettsia rickettsii.

Because of the potential significance of external components of the obligate intracellular parasite Rickettsia rickettsii in host-parasite interactions, we have begun the first phase of a study to isolate and characterize surface antigens of this organism. An antiserum to a rickettsial surface component was obtained from rabbits inoculated with immune precipitates prepared by crossed immunoelectrophoresis of Triton X-100 extracts of R. rickettsii strain R. This antiserum (i) protected guinea pigs inoculated with 10,000 guinea pig 50% infectious doses of R. rickettsii against fever, (ii) preven…

Experimental infection of the cotton rat Sigmodon hispidus with Rickettsia rickettsii.

Studies of experimental infection of the cotton rat, Sigmodon hispidus, with the virulent Sheila Smith (R type) and the avirulent Si 7 (U type) strains of Rickettsia rickettsii were undertaken to evaluate the role of this native wild mammal in the ecology of Rocky Mountain spotted fever. The Sheila Smith strain, which was highly lethal for guinea pigs, was nonpathogenic for cotton rats. Serial passage of the R-type strain in the cotton rat did not alter the virulence of the agent for cotton rats or guinea pigs. The U-type strain, which was originally recovered from a wild cotton rat, could not…

Evaluation of a PCR assay for quantitation of Rickettsia rickettsii and closely related spotted fever group rickettsiae.

A spotted fever rickettsia quantitative PCR assay (SQ-PCR) was developed for the detection and enumeration of Rickettsia rickettsii and other closely related spotted fever group rickettsiae. The assay is based on fluorescence detection of SYBR Green dye intercalation in a 154-bp fragment of the rOmpA gene during amplification by PCR. As few as 5 copies of the rOmpA gene of R. rickettsii can be detected. SQ-PCR is suitable for quantitation of R. rickettsii and 10 other genotypes of spotted fever group rickettsiae but not for R. akari, R. australis, R. bellii, or typhus group rickettsiae. The se…

Comparative susceptibility to mouse interferons of Rickettsia tsutsugamushi strains with different virulence in mice and of Rickettsia rickettsii.

Three strains of Rickettsia tsutsugamushi (Karp, Gilliam, and TA716, representing three virulence types in mice) were examined for their sensitivity to the inhibitory effects of recombinant gamma interferon (IFN-gamma) and purified IFN-alpha/beta in two cultured mouse fibroblast cell lines. The susceptibilities of another species, Rickettsia rickettsii, and of encephalomyocarditis virus (EMCV) were also tested for comparative purposes. IFN-gamma inhibited rickettsial replication in only one of the six combinations of R. tsutsugamushi strains and mouse cells (strain Gilliam and the BALB/c mouse…

Isolation of Rickettsia rickettsii in Rocky Mountain Spotted Fever Outbreak, Panama.

We report new cases of Rocky Mountain spotted fever in patients from Kinkantu, Ngäbe-Bugle indigenous comarca, Panama. We isolated Rickettsia rickettsii in cell culture after intraperitoneal inoculation of guinea pigs with tissues from a deceased patient. Our results indicate that Rocky Mountain spotted fever is emerging in this region.

Lethal effect of Rickettsia rickettsii on its tick vector (Dermacentor andersoni).

Rickettsia rickettsii, the causative agent of Rocky Mountain spotted fever, was lethal for the majority of experimentally and transovarially infected Rocky Mountain wood ticks (Dermacentor andersoni). Overall, 94.1% of nymphs infected as larvae by feeding on rickettsemic guinea pigs died during the molt into adults and 88. 3% of adult female ticks infected as nymphs died prior to feeding. In contrast, only 2.8% of uninfected larvae failed to develop into adults over two generations. Infected female ticks incubated at 4 degreesC had a lower mortality (80.9%) than did those held at 21 degreesC (…

Development of inducible promoter and CRISPRi plasmids functional in Rickettsia rickettsii.

UNLABELLED: Rickettsia rickettsii is an obligate intracellular, tick-borne bacterium that causes Rocky Mountain spotted fever. The demanding nature of cultivating these bacteria within host cells and the labor involved in obtaining clonal isolates have severely limited progress regarding the development of compatible genetic tools to study this pathogen. Conditional expression of genes that might be toxic or have an otherwise undesirable effect is the next logical goal to expand upon the constitutive expression plasmids generated thus far. We describe the construction of an inducible promoter …

Сообщение о скульптуме Амблиоммы в доме в районе циркуляции Рикетсии.

Amblyomma sculptum — это клещ, имеющий медицинское и ветеринарное значение, так как в Бразилии он является главным вектором Рикитсии рикеттси, болезни, затрагивающей людей. Присутствие клещей было замечено вне резиденции в пригородном районе Атлантического леса в Бразилии, а также на двух собаках, которые там жили. Восемнадцать взрослых скульптумов были замечены на цементированном столбе у крыльца дома и в укрытии внутри трещин столба; в то же время на собаках были найдены только сингуанные клещи Ripicephalus sanguineus sensu lato. Согласно гипотезе, по мере распространения собак в лесных райо

Совпадение в аннотации оригинала
Amblyomma sculptum is a tick that has medical and veterinary importance as, in Brazil, it is the main vector of Rickettsia rickettsii, a disease affecting humans. The presence of ticks was observed outside a residence in a peri-urban area of the Atlantic Forest region in Brazil, as well as on two dogs that lived there. Eighteen A. sculptum adults were seen w…

Prevalence of Rickettsia rickettsii in Ticks: Systematic Review and Meta-Analysis.

Background and Objectives:Rickettsia rickettsii is a pathogen that is known to cause spotted fever, a zoonosis that is endemic in several regions of the Americas. However, no systematic review and meta-analysis has been conducted to estimate the prevalence of this rickettsial disease in the Americas. Therefore, the objective of this study was to estimate the prevalence of R. rickettsii in ticks in the Americas. Methods: The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed and data were retrieved from four electronic databases: MEDLINE/PubMed,…

Detection of Bartonella spp. in dogs after infection with Rickettsia rickettsii.

BACKGROUND: Dynamics of infection by Bartonella and Rickettsia species, which are epidemiologically associated in dogs, have not been explored in a controlled setting. OBJECTIVES: Describe an outbreak investigation of occult Bartonella spp. infection among a group of dogs, discovered after experimentally induced Rickettsia rickettsii (Rr) infection. ANIMALS: Six apparently healthy purpose-bred Beagles obtained from a commercial vendor. METHODS: Retrospective and prospective study. Dogs were serially tested for Bartonella spp. and Rr using serology, culture, and PCR, over 3 study phases: 3 m…

[Severe spotted fever by Rickettsia rickettsii, in tourist in the Argentine Northwest].

On the fifth day after leaving the Parque Nacional El Rey, province of Salta, Argentina, where she made rural tourism, a woman of Italian origin, aged 47, developed an acute fever followed by a petechial and purpuric rash that progressed rapidly to multiorgan failure. She died on the sixth day after hospitalization. There were references to tick bites and a skin lesion similar to tache noire was found. The autopsy showed generalized vasculitis, ascites, pulmonary edema, acute tubular necrosis and portal centrilobular necrosis. Spleen and liver tissue were processed for PCR Rickettsia spp, base

Comparative genome sequencing of Rickettsia rickettsii strains that differ in virulence.

Rickettsia rickettsii is an obligate intracellular pathogen that is the causative agent of Rocky Mountain spotted fever. Strains of R. rickettsii differ dramatically in virulence. In a guinea pig model of infection, the severity of disease as assessed by fever response varies from the most virulent, Sheila Smith, to Iowa, which causes no fever. To identify potential determinants of virulence in R. rickettsii, the genomes of two additional strains were sequenced for comparison to known sequences (comparative genome sequencing [CGS]). R. rickettsii Morgan and R strains were compared to the aviru…

Ultrastructure of Rickettsia rickettsii actin tails and localization of cytoskeletal proteins.

Actin-based motility (ABM) is a mechanism for intercellular spread that is utilized by vaccinia virus and the invasive bacteria within the genera Rickettsia, Listeria, and Shigella. Within the Rickettsia, ABM is confined to members of the spotted fever group (SFG), such as Rickettsia rickettsii, the agent of Rocky Mountain spotted fever. Infection by each agent induces the polymerization of host cell actin to form the typical F (filamentous)-actin comet tail. Assembly of the actin tail propels the pathogen through the host cytosol and into cell membrane protrusions that can be engulfed by neig…

Adherence of platelets to human endothelial cells infected by Rickettsia rickettsii.

Rickettsia rickettsii, the etiologic agent of Rocky Mountain spotted fever, causes widespread vasculitis due to extensive injury of endothelial cells lining small blood vessels. Injury to these cells can lead to denudation of the endothelial lining and exposure of the thrombogenic subendothelium. Modification of the cell surface, either through minor trauma or as a result of altered cell surface biochemistry, could induce changes reflected in increased platelet reactivity. Because membrane modification is likely when R. rickettsii enters endothelial cells, the possibility that infection by thi…

Reactivation of Rickettsia rickettsii in Dermacentor andersoni ticks: an ultrastructural analysis.

Virulent Rickettsia in Dermacentor andersoni lose their pathogenicity and virulence for guinea pigs when subjected to physiological stresses, such as starvation (overwintering), of its tick vector. However, incubation of infected ticks at an elevated temperature (37 degrees C) for 24 to 48 h or feeding for a time (usually greater than 10 h) induces R. rickettsii to revert to a virulent state, a phenomenon defined as "reactivation." Electron microscopy reveals that the microcapsular and slime layers of R. rickettsii undergo changes dependent upon the physiological conditions within the tick vec

Demonstration of Rickettsia rickettsii in the rhesus monkey by immune fluorescence microscopy.

Indirect immune fluorescence was used to detect rickettsiae in the tissues of a primate inoculated subcutaneously with Rickettsia rickettsii. Rickettsiae were identified by indirect immuno fluorescence predominantly in skin, skeletal muscle, scrotum, testicles, nares, heart, kidney, liver, brain, spleen, pancreas, and larynx. Cell culture assay confirmed the presence of infectious organisms in those specimens.

Разрушение рикетсайского автотранспортера " Рикетсия " (Rickettsia rickettsii Sca2) препятствует функционированию мочевого аппарата.

Рикеттсий Рикеттси, этиологический агент Рокки Маунтин (Rickettsii rickettsii), обнаруживает лихорадку, воспроизводит внутри цитозола инфицированных клеток и использует живую силу для межклеточного и внутриклеточного распространения. Несмотря на то, что ультраструктура связанных с ней белков и белков-актинов отличается от белков Листерии или Сигеллы, относительно мало известно о рикетсиальных белках, участвующих в ее организации. Здесь мы использовали случайный транспозон мутагенез Р. Ррикеттсии для создания маленького мутатата, который несовершенен в силу действия мольбы и не распространяется

Rickettsia rickettsii-induced cellular injury of human vascular endothelium in vitro.

The endothelial cell is the putative primary target cell in humans infected with Rickettsia rickettsii, the etiological agent of Rocky Mountain spotted fever. Although the clinical manifestations of infection by this organism are well documented, the mechanism of injury to the endothelial cell is not understood. The ability to culture human endothelial cells in vitro provides a unique system with which to study this host-parasite interaction directly. Human vascular endothelial cells derived from the umbilical vein, when infected by R. rickettsii, became severely damaged within a few days post…