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Vector competence and transovarial transmission of Rickettsia rickettsii in Rickettsia bellii-infected and -uninfected Amblyomma dubitatum ticks.

Brazilian spotted fever (BSF) is endemic in southeastern Brazil, where Amblyomma sculptum is the main vector incriminated in the transmission of R. rickettsii to humans. In many BSF-endemic areas capybaras are the main hosts for A. sculptum and also efficient amplifiers of R. rickettsii for this tick species. Capybaras are also primary hosts for Amblyomma dubitatum, a tick species frequently found infected by Rickettsia bellii but with no records of natural infection by R. rickettsii. The present study aimed to evaluate transovarial transmission and vector competence for R. rickettsii in A. du

Detection of Rickettsia rickettsii, Rickettsia parkeri, and Rickettsia akari in skin biopsy specimens using a multiplex real-time polymerase chain reaction assay.

BACKGROUND: Rickettsia rickettsii, Rickettsia parkeri, and Rickettsia akari are the most common causes of spotted fever group rickettsioses indigenous to the United States. Infected patients characteristically present with a maculopapular rash, often accompanied by an inoculation eschar. Skin biopsy specimens are often obtained from these lesions for diagnostic evaluation. However, a species-specific diagnosis is achieved infrequently from pathologic specimens because immunohistochemical stains do not differentiate among the causative agents of spotted fever group rickettsiae, and existing pol…

A rapid isothermal RPA-CRISPR/Cas12a assay for detection of Rickettsia rickettsii.

INTRODUCTION: Rocky Mountain spotted fever (RMSF) resulting from the tick-borne Rickettsia rickettsii infections is a potentially fatal tick-borne disease affecting humans and dogs in the Americas. It is difficult to confirm the diagnosis early in the laboratory on account of low-level and inconsistent rickettsemia in whole blood. METHODS: Here we established a fast, fully isothermal RPA-CRISPR/Cas12a assay that targeted the vitamin uptake transporter (vut) gene of R. rickettsii. Two independent crRNA primer sets (104 bp and 92 bp) were developed to independently amplify the gene target to en…

Proteolytic Cleavage of the Immunodominant Outer Membrane Protein rOmpA in Rickettsia rickettsii.

Rickettsia rickettsii, the causative agent of Rocky Mountain spotted fever, contains two immunodominant proteins, rOmpA and rOmpB, in the outer membrane. Both rOmpA and rOmpB are conserved throughout spotted fever group rickettsiae as members of a family of autotransporter proteins. Previously, it was demonstrated that rOmpB is proteolytically processed, with the cleavage site residing near the autotransporter domain at the carboxy-terminal end of the protein, cleaving the 168-kDa precursor into apparent 120-kDa and 32-kDa fragments. The 120- and 32-kDa fragments remain noncovalently associate…

Molecular characterization of Rickettsia rickettsii infecting dogs and people in North Carolina.

Rocky Mountain spotted fever (RMST) is an important cause of morbidity and mortality in people and dogs in the United States. Disease manifestations are strikingly similar in both species, and illness in dogs can precede illness in people. R. rickettsii has been identified as a Select Agent by the CDC as a Category C priority pathogen by the National Institute of Allergic and Infectious Diseases because it is amenable to use as a bioterror agent. The clinical and temporal relationship of naturally occurring diseases in dogs and people suggests that dogs could serve as sentinels for natural inf

Role of phospholipase-associated penetration mechanism in cell injury by Rickettsia rickettsii.

The cholesterol receptor-binding drugs amphotericin B and digitonin reduced rickettsial plaque formation, presumably by blocking rickettsial attachment, even when added to the plaque model on day 4 post-inoculation when infected foci were well established. The phospholipase inhibitor phentermine reduced plaque formation, presumably by inhibiting the phospholipase-associated entry step of penetration.

Domestic dogs as amplifying hosts of Rickettsia rickettsii for Amblyomma aureolatum ticks.

Brazilian spotted fever (BSF) is an acute infectious disease caused by the bacterium Rickettsia rickettsii, which is transmitted by different tick species. Due to deleterious effects caused on ticks, the horizontal transmission of R. rickettsii through amplifying hosts is crucial for its maintenance in tick populations among BSF-endemic areas. The tick Amblyomma aureolatum is the main vector of R. rickettsii in the São Paulo metropolitan area; nevertheless, it is not known which vertebrate could act as an amplifying host for this tick species. Herein, we evaluated the potential of domestic dog…

Phylogeography of Rickettsia rickettsii genotypes associated with fatal Rocky Mountain spotted fever.

Rocky Mountain spotted fever (RMSF), a tick-borne zoonosis caused by Rickettsia rickettsii, is among the deadliest of all infectious diseases. To identify the distribution of various genotypes of R. rickettsii associated with fatal RMSF, we applied molecular typing methods to samples of DNA extracted from formalin-fixed, paraffin-embedded tissue specimens obtained at autopsy from 103 case-patients from seven countries who died of RMSF. Complete sequences of one or more intergenic regions were amplified from tissues of 30 (29%) case-patients and revealed a distribution of genotypes consisting o…

Evaluation of immunoperoxidase techniques to detect Rickettsia rickettsii in fixed tissue sections.

Standard immunoperoxidase techniques were evaluated in the diagnosis of Rocky Mountain spotted fever (RMSF). Formalin-fixed, paraffin-embedded tissue was tested to detect Rickettsia rickettsii using the same antibody provided by the Centers for Disease Control and Prevention that is used for direct immunofluorescence (DIF). Tissues from 23 patients with suspected RMSF were divided: some were snap-frozen for DIF; the remainder were fixed in formalin, processed routinely, and embedded in paraffin for immunoperoxidase and hematoxylin and eosin staining. Ten patients were ultimately determined to …

Идентификация Рикитсии рикетси в формализованных тканях с парафинами по иммунной флюоресценции.

С небольшим модификацией методов пищеварения трипсина Рикетсиа рикеттсии была продемонстрирована конкретно иммунофлюоресцентной пятнистостью в пятнах тканей, покрытых формальным слоем парафина, от человека, резусной обезьяны и подопытной свиньи с пятнами Рокки Маунтин и в инфицированных мембранах из куриного эмбриона. Ткани были вырезаны на 4 микрона и, используя гелтен в качестве клейки для тканей, были обработаны в обычном порядке. После этого секции переваривались в рефрижераторный 0,1% трипсина в течение 16 часов, промывались и пятна специально для R. rickettsii в результате прямой или кос

Совпадение в аннотации оригинала
With slight modification of a trypsin digestion technique, Rickettsia rickettsii were demonstrated specifically by immunofluorescence staining in Formalin-fixed, paraffin-embedded tissue sections from a human, rhesus monkey, and guinea pig with Rocky Mountain spotted fever and in infected membranes from a chicken embryo. Tissues were cut at 4 micron and, usi…

Rickettsia rickettsii infection as an unusual cause of pediatric retinitis: A case report.

PURPOSE: To report a case of infectious pediatric retinitis attributed to Rocky Mountain spotted fever which is rarely reported in the Unite … humans by infected ticks. Rickettsial infections, including Rocky Mountain spotted fever caused by Rickettsia rickettsii, are a cause of infectious retinitis, and atypical and zoonotic infections should remain on the differential diagnosis for patients presenting with rash, systemic illness, and visual complaints, even if the patient's travel or exposure history do no …

Immunoperoxidase and immunofluorescent staining of Rickettsia rickettsii in skin biopsies. A comparative study.

OBJECTIVE: To compare immunofluorescent and immunoperoxidase staining of Rickettsia rickettsii in skin biopsies of patients suspected of having Rocky Mountain spotted fever (RMSF). DESIGN: Immunofluorescent staining results for R rickettsii from skin biopsies of patients suspected of having RMSF were obtained by computer and chart review. Immunoperoxidase staining for R rickettsii was performed on formalin-fixed, paraffin-embedded skin biopsies from the same patient population. PATIENTS: Twenty-six patients who were clinically suspected of having RMSF were included in this study. Skin biopsi…

A cluster of Rickettsia rickettsii infection at an animal shelter in an urban area of Brazil.

Rickettsia rickettsii infection is being increasingly recognized as an important cause of fatal acute illness in Brazil, where this tick-borne disease is designated Brazilian spotted fever (BSF). In this study we report five fatal cases of BSF in employees of an animal shelter in an urban area in the municipality of Rio de Janeiro in southeast Brazil after a natural disaster on 11 January 2011. Four of the cases occurred from 27 January to 11 April 2011, while the fifth fatal case was identified in April 2012. Three cases were confirmed by molecular analysis and two by epidemiological linkage.…

Rickettsia rickettsii outer membrane protein YbgF induces protective immunity in C3H/HeN mice.

Rickettsia rickettsii is the etiological agent of Rocky Mountain spotted fever (RMSF). YbgF and TolC are outer membrane-associated proteins of R. rickettsii that play important roles in its interaction with host cells. We investigated the immunogenicity of YbgF and TolC for protection against RMSF. We immunized C3H/HeN mice with recombinant R. rickettsii YbgF (rYbgF) or TolC (rTolC). Rickettsial burden and impairment in the lungs, spleens, and livers of rYbgF-immunized mice were significantly lower than in rTolC-immunized mice. The ratio of IgG2a to IgG1 in rYbgF-immunized mice continued to in…

Detection of Rickettsia rickettsii and Bartonella henselae in Rhipicephalus sanguineus ticks from California.

Sixty-two questing adult Rhipicephalus sanguineus (Latreille) ticks were collected by direct removal from blades of turfgrass and adjacent c … DNAs were detected using nested PCR for their 16S rRNA genes. These findings extend the area where Rickettsia rickettsii may be vectored by Rh. sanguineus. Rh. sanguineus also may be infected with Bartonella henselae, a human pathogen that is typically associated with fleas and causes cat scratch disease.

First finding of Rickettsia rickettsii in Haemaphysalis longicornis (Acari: Ixodidae) in North America.

Rocky Mountain spotted fever (RMSF) is a tick-borne infection caused by Rickettsia rickettsii Brumpt, which is included in the spotted fever group (SFG) rickettsioses. In the United States, RMSF is transmitted primarily by ticks in the genus Dermacentor and in parts of Arizona and northern Mexico, by Rhipicephalus sanguineus Latreille. SFG rickettsiosis cases have been reported throughout the United States, but between 2018 and 2022, 5 states (Alabama, Arkansas, Missouri, North Carolina, and Tennessee) accounted for over 50% of SFG rickettsiosis cases. The most virulent of the spotted fever gr…

TRIM56-mediated production of type I interferon inhibits intracellular replication of Rickettsia rickettsii.

UNLABELLED: Rickettsia rickettsii (R. rickettsii), the causative agent of Rocky Mountain spotted fever (RMSF), is the most pathogenic member among Rickettsia spp. Previous studies have shown that tripartite motif-containing 56 (TRIM56) E3 ligase-induced ubiquitination of STING is important for cytosolic DNA sensing and type I interferon production to induce anti-DNA viral immunity, but whether it affects intracellular replication of R. rickettsii remains uncharacterized. Here, we investigated the effect of TRIM56 on HeLa and THP-1 cells infected with R. rickettsii. We found that the expression…

A protective protein antigen of Rickettsia rickettsii has tandemly repeated, near-identical sequences.

The nucleotide sequence of a Rickettsia rickettsii gene that encodes a high-molecular-mass surface antigen (190 kilodaltons), which elicits protective immunity, was determined. The 6,747-nucleotide gene coded for a 2,249-amino-acid protein with a calculated molecular weight of 224,321. A 3.8-kilobase PstI fragment proximal to the 5' end of the gene was found to consist of 13 highly related tandem repeats which constituted over 40% of the coding region. The repeated sequences could be divided into either a 225-nucleotide, 75-amino-acid unit (type I) or a 216-nucleotide, 72-amino-acid unit (type…

Extraction of protective components of Rickettsia rickettsii with n-octyl-beta-D-glucopyranoside.

Two Rickettsia rickettsii proteins, with apparent molecular masses of 120 and 155 kilodaltons, have been implicated as important antigens in immunity to Rocky Mountain spotted fever. An n-octyl-beta-D-glucopyranoside-soluble fraction of R. rickettsii was found to be enriched for these proteins along with others. Vaccination of mice with the detergent-soluble fraction protected them against death caused by R. rickettsii and protected guinea pigs from developing Rocky Mountain spotted fever after being challenged with viable R. rickettsii.