Proteomic analysis of Rickettsia akari proposes a 44 kDa-OMP as a potential biomarker for Rickettsialpox diagnosis.

BACKGROUND: Rickettsialpox is a febrile illness caused by the mite-borne pathogen Rickettsia akari. Several cases of this disease are reported worldwide annually. Nevertheless, the relationship between the immunogenicity of R. akari and disease development is still poorly understood. Thus, misdiagnosis is frequent. Our study is aiming to identify immunogenic proteins that may improve disease recognition and enhance subsequent treatment. To achieve this goal, two proteomics methodologies were applied, followed by immunoblot confirmation. RESULTS: Three hundred and sixteen unique proteins were identified in the whole-cell extract of R. akari. The most represented protein groups were found to be those involved in translation, post-translational modifications, energy production, and cell wall development. A significant number of proteins belonged to amino acid transport and intracellular trafficking. Also, some proteins affecting the virulence were detected. In silico analysis of membrane enriched proteins revealed 25 putative outer membrane proteins containing beta-barrel structure and 11 proteins having a secretion signal peptide sequence. Using rabbit and human sera, various immunoreactive proteins were identified from which the 44 kDa uncharacterized protein (A8GP63) has demonstrated a unique detection capability. It positively distinguished the sera of patients with Rickettsialpox from other rickettsiae positive human sera. CONCLUSION: Our proteomic analysis certainly contributed to the lack of knowledge of R. akari pathogenesis. The result obtained may also serve as a guideline for a more accurate diagnosis of rickettsial diseases. The identified 44 kDa uncharacterized protein can be certainly used as a unique marker of rickettsialpox or as a target molecule for the development of more effective treatment.

Investigating the histopathological findings and immunolocalization of rickettsialpox infection in skin biopsies: A case series and review of the literature.

BACKGROUND: Recognition of rickettsialpox infection on skin biopsy can be challenging. The histopathology is non-specific and inconsistently described. We assess classic histopathologic features in confirmed cases and review the literature. METHODS: We searched for cases of "rickettsialpox" diagnosed between 2006 and 2018 with positive immunostaining for Spotted Fever Group Rickettsia species. Original slides were evaluated for vacuolar alterations, granulomatous inflammation, vasculitis, necrosis, fibrin thrombi, microvesiculation, papillary dermal edema, and extravasated red blood cells. All biopsies were stained for CD3, CD20, CD68, and myeloperoxidase. RESULTS: Six biopsy specimens were compiled, three of which were sampled from vesiculopapules, one from a maculopapule, and two from eschars. Vacuolar alterations and vasculitis were present in all specimens (6/6; 100%). Granulomatous inflammation was present in five specimens (5/6; 83.3%). Fibrin thrombi and red blood cells were seen in 3/6 (50%) of specimens. The eschars showed necrosis of the epidermis and superficial dermis (2/6, 33.3%). Only one specimen showed intraepidermal vesiculation and papillary dermal edema (1/6; 16.7%). All six specimens showed perivascular infiltration with CD3+ T-cells, and low amounts of CD20+ B-cells and neutrophils. Five of the six specimens (83.3%) showed significant levels of CD68+ histiocytes. CONCLUSION: The histopathology of rickettsialpox infection is septic lymphocytic and granulomatous vasculitis.

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 polymerase chain reaction (PCR) assays generally target large gene segments that may be difficult or impossible to obtain from formalin-fixed tissues. METHODS: This work describes the development and evaluation of a multiplex real-time PCR assay for the detection of these 3 Rickettsia species from formalin-fixed, paraffin-embedded (FFPE) skin biopsy specimens. RESULTS: The multiplex PCR assay was specific at discriminating each species from FFPE controls of unrelated bacterial, viral, protozoan, and fungal pathogens that cause skin lesions, as well as other closely related spotted fever group Rickettsia species. CONCLUSIONS: This multiplex real-time PCR demonstrates greater sensitivity than nested PCR assays in FFPE tissues and provides an effective method to specifically identify cases of Rocky Mountain spotted fever, rickettsialpox, and R. parkeri rickettsiosis by using skin biopsy specimens.

A case of rickettsialpox in Northern Europe.

We report the first case of rickettsialpox caused by Rickettsia akari in the Netherlands. The diagnosis was suspected based on clinical grounds and was confirmed by Western blot analysis with cross-adsorption. Because the arthropod vector (Liponyssoides sanguineus) is ubiquitous, we suspect that the disease is under-diagnosed in non-endemic areas.

Rickettsiosis Variceliforme o Viruela Rickettsiósica / Varicelliform Rickettsiosis or Rickettsial pox

El género de las Rickettsias tiene como característica ser bacterias gramnegativas intracelulares que precisan de un vector para su transmisión. Las fiebres exantemáticas producidas por Rickettsias son endémicas en nuestra región (Albacete), sobre todo en áreas rurales. Se presenta el caso de un paciente con una variedad inusual de enfermedad producida por Rickettsias, caracterizada por lesiones papulovesiculosas (AU)

Rickettsia is a genus of intracellular, gram-negative bacteria that requires a vector for transmission. Spotted fever caused by Rickettsia is endemic in our region (Albacete), especially in rural areas. We present a patient with an unusual variety of Rickettsial disease, characterised by papulovesicular lesions (AU)

Involvement of TLR2 and TLR4 in cell responses to Rickettsia akari.

A better understanding of the pathogenesis of rickettsial disease requires elucidation of mechanisms governing host defense during infection. TLRs are primary sensors of microbial pathogens that activate innate immune cells, as well as initiate and orchestrate adaptive immune responses. However, the role of TLRs in rickettsia recognition and cell activation remains poorly understood. In this study, we examined the involvement of TLR2 and TLR4 in recognition of Rickettsia akari, a causative agent of rickettsialpox. Transfection-based complementation of TLR2/4-negative HEK293T cells with human TLR2 or TLR4 coexpressed with CD14 and MD-2 enabled IκB-α degradation, NF-κB reporter activation, and IL-8 expression in response to heat-killed (HK) R. akari. The presence of the R753Q TLR2 or D299G TLR4 polymorphisms significantly impaired the capacities of the respective TLRs to signal HK R. akari-mediated NF-κB reporter activation in HEK293T transfectants. Blocking Ab against TLR2 or TLR4 markedly inhibited TNF-α release from human monocytes stimulated with HK R. akari, and TNF-α secretion elicited by infection with live R. akari was reduced significantly only upon blocking of TLR2 and TLR4. Live and HK R. akari exerted phosphorylation of IRAK1 and p38 MAPK in 293/TLR4/MD-2 or 293/TLR2 stable cell lines, whereas only live bacteria elicited responses in TLR2/4-negative HEK293T cells. These data demonstrate that HK R. akari triggers cell activation via TLR2 or TLR4 and suggest use of additional TLRs and/or NLRs by live R. akari.

A dog naturally infected with Rickettsia akari in Yucatan, México.

Rickettsia akari is the causative agent of rickettsialpox, a primarily urban mite-borne rickettsiosis that is encountered in the United States and in a few countries around the world. Its vector is the mite Liponyssoides sanguineus, which is found on rats and mice, which serve as reservoirs for the disease. In this work we report a severe animal case of R. akari infection with two unusual features: R. akari was found in a dog, and its potential vector was a tick.

[Contribution of all-USSR (Russian) Center of Rickettsioses and Collaboration Centre of WHO to the study of rickettsioses of tick-borne spotted fever group].

The manuscript presents the results of studies of rickettsioses of spotted fever group in the territories of USSR (Russia) and ChSSR (Slovakia). Authors review data about isolation of strains of rickettsiae of spotted fever group, improvement of isolation techniques, diagnostics and diagnostic preparations.

Hepatitis in association with rickettsialpox.

Rickettsialpox is an acute, self-limited, febrile illness caused by Rickettsia akari and transmitted by Liponyssoides sanguineus, a mite that infests the common house mouse, Mus musculus. Liver involvement in rickettsialpox has received little attention, although hepatitis has been reported in several other rickettsial infections. In this report, we describe two patients with rickettsialpox who had acute hepatitis that resolved completely. In the appropriate clinical setting, rickettsialpox should be considered in the differential diagnosis of hepatitis.

Serologic evidence of a Rickettsia akari-like infection among wild-caught rodents in Orange County and humans in Los Angeles County, California.

We detected antibodies reactive with Rickettsia akari, the etiologic agent of rickettsialpox in humans and in 83 of 359 (23%) rodents belonging to several species, collected in Orange County, CA. Reciprocal antibody titers >1:16 to R. akari were detected in native mice and rats (Peromyscus maniculatus, P. eremicus, and Neotoma fuscipes) and in Old World mice and rats (Mus musculus, Rattus rattus, and R. norvegicus), representing the first time that antibodies reactive with this agent have been detected in four of these species and the first report of these antibodies in rodents and humans west of the Mississippi River. We then tested serum samples from individuals who used a free clinic in downtown Los Angeles and found that 25 of 299 (8%) of these individuals had antibody titers >1:64 to R. akari. Serologic evidence suggested that R. akari or a closely related rickettsia is prevalent among several rodent species at these localities and that infection spills over into certain segments of the human population. Isolation or molecular confirmation of the agent is needed to conclusively state that R. akari is the etiologic agent infecting these rodents.

Isolation of Rickettsia akari from eschars of patients with rickettsialpox.

Rickettsialpox is a cosmopolitan, mite-borne, spotted fever rickettsiosis caused by Rickettsia akari. The disease is characterized by a primary eschar, fever, and a papulovesicular rash. Rickettsialpox was first identified in New York City in 1946 and the preponderance of recognized cases in the United States continues to originate from this large metropolitan center. The most recently isolated U.S. strain of R. akari was obtained more than a half century ago. We describe the culture and initial characterization of five contemporaneous isolates of R. akari obtained from eschar biopsy specimens from New York City patients with rickettsialpox. This work emphasizes the importance and utility of culture-and molecular-based methods for the diagnosis of rickettsialpox and other eschar-associated illnesses.

[Rickettsialpox: report of two cases imported from South Africa]. / Rickettsialpox: descrizione di due casi clinici importati dal Sud Africa.

Rickettsialpox is a rickettsiosis characterized clinically by an escar, fever and papulovescicular eruption. The author reports two cases imported from South Africa.

Increased detection of rickettsialpox in a New York City hospital following the anthrax outbreak of 2001: use of immunohistochemistry for the rapid confirmation of cases in an era of bioterrorism.

BACKGROUND: Rickettsialpox is a self-limited febrile illness with skin lesions that may be mistaken for signs of potentially more serious diseases, such as cutaneous anthrax or chickenpox. The cluster of cutaneous anthrax cases from bioterrorism in October 2001 likely heightened awareness of and concern for cutaneous eschars. OBJECTIVES: To apply an immunohistochemical technique on paraffin-embedded skin biopsy specimens for diagnosing rickettsialpox, and to compare the reported incidence of rickettsialpox before, during, and after the cluster of cutaneous anthrax cases. DESIGN: Case series. SETTING: Dermatology department in a large tertiary care hospital in New York City. PATIENTS: Eighteen consecutive patients with the clinical diagnosis of rickettsialpox from February 23, 2001, through October 31, 2002. MAIN OUTCOME MEASURES: Results of immunohistochemical testing of skin biopsy specimens and of serological testing. RESULTS: Immunohistochemical testing revealed spotted fever group rickettsiae in all 16 eschars and in 5 of the 9 papulovesicles tested. A 4-fold or greater increase in IgG antibody titers reactive with Rickettsia akari was observed in all 9 patients for whom acute and convalescent phase samples were available; 6 patients had single titers indicative of rickettsialpox infection (> or =1:64). Of the 18 patients, 9 (50%) presented in the 5 months following the bioterrorism attacks. CONCLUSIONS: Rickettsialpox remains endemic in New York City, and the bioterrorism attacks of October 2001 may have led to increased awareness and detection of this disease. Because rickettsialpox may be confused with more serious diseases, such as cutaneous anthrax or chickenpox, clinicians should be familiar with its clinical presentation and diagnostic features. Immunohistochemical staining of skin biopsy specimens, particularly from eschars, is a sensitive technique for confirming the clinical diagnosis.

Rickettsialpox in New York City: a persistent urban zoonosis.

Rickettsialpox, a spotted fever rickettsiosis, was first identified in New York City (NYC) in 1946. During the next five years, approximately 540 additional cases were identified in NYC. However, during the subsequent five decades, rickettsialpox received relatively little attention from clinicians and public health professionals, and reporting of the disease diminished markedly. During February 2001 through August 2002, 34 cases of rickettsialpox in NYC were confirmed at CDC from cutaneous biopsy specimens tested by using immunohistochemical (IHC) staining, PCR analysis, and isolation of Rickettsia akari in cell culture, as well as an indirect immunofluorescence assay of serum specimens. Samples were collected from patients with febrile illnesses accompanied by an eschar, a papulovesicular rash, or both. Patients originated predominantly from two boroughs (Manhattan and the Bronx). Only 8 (24%) of the cases were identified prior to the reports of bioterrorism-associated anthrax in the United States during October 2001, and lesions of several patients evaluated during and subsequent to this episode were suspected initially to be cutaneous anthrax. IHC staining of biopsy specimens of eschars and papular lesions were positive for spotted fever group rickettsiae for 32 patients. Of the eleven patients for whom paired serum samples were obtained, all demonstrated fourfold or greater increases in antibody titers reactive with R. akari. The 17-kDa protein gene sequence of R. akari was amplified from eschars of five patients. Four isolates of R. akari were obtained from cutaneous lesions. Possible factors responsible for the increase in clinical samples evaluated for rickettsialpox during this interval include renewed clinical interest in the disease, improved diagnostic methods, epizootiological influences, and factors associated with the recent specter of bioterrorism.