Interferon receptor-deficient mice are susceptible to eschar-associated rickettsiosis.

Arthropod-borne rickettsial pathogens cause mild and severe human disease worldwide. The tick-borne pathogen Rickettsia parkeri elicits skin lesions (eschars) and disseminated disease in humans; however, inbred mice are generally resistant to infection. We report that intradermal infection of mice lacking both interferon receptors (Ifnar1-/-;Ifngr1-/-) with as few as 10 R. parkeri elicits eschar formation and disseminated, lethal disease. Similar to human infection, eschars exhibited necrosis and inflammation, with bacteria primarily found in leukocytes. Using this model, we find that the actin-based motility factor Sca2 is required for dissemination from the skin to internal organs, and the outer membrane protein OmpB contributes to eschar formation. Immunizing Ifnar1-/-;Ifngr1-/- mice with sca2 and ompB mutant R. parkeri protects against rechallenge, revealing live-attenuated vaccine candidates. Thus, Ifnar1-/-;Ifngr1-/- mice are a tractable model to investigate rickettsiosis, virulence factors, and immunity. Our results further suggest that discrepancies between mouse and human susceptibility may be due to differences in interferon signaling.

Tick bites allow disease-causing microbes, including multiple species of Rickettsia bacteria, to pass from arthropods to humans. Being exposed to Rickettsia parkeri, for example, can cause a scab at the bite site, fever, headache and fatigue. To date, no vaccine is available against any of the severe diseases caused by Rickettsia species. Modelling human infections in animals could help to understand and combat these illnesses. R. parkeri is a good candidate for such studies, as it can give insight into more severe Rickettsia infections while being comparatively safer to handle. However, laboratory mice are resistant to this species of bacteria, limiting their use as models. To explore why this is the case, Burke et al. probed whether an immune mechanism known as interferon signalling protects laboratory rodents against R. parkeri. During infection, the immune system releases molecules called interferons that stick to 'receptors' at the surface of cells, triggering defense mechanisms that help to fight off an invader. Burke et al. injected R. parkeri into the skin of mice that had or lacked certain interferon receptors, showing that animals without two specific receptors developed scabs and saw the disease spread through their body. Further investigation showed that two R. parkeri proteins, known as OmpB or Sca2, were essential for the bacteria to cause skin lesions and damage internal organs. Burke et al. then used R. parkeri that lacked OmpB or Sca2 to test whether these modified, inoffensive microbes could act as 'vaccines'. And indeed, vulnerable laboratory mice which were first exposed to the mutant bacteria were then able to survive the 'normal' version of the microbe. Together, this work reveals that interferon signalling protects laboratory mice against R. parkeri infections. It also creates an animal model that can be used to study disease and vaccination.

Ultrastructure of intracytoplasmic Rickettsia-like infection of the gills of the teleost Archosargus probatocephalus (Sparidae) in northeastern Brazil.

A histopathological survey was conducted to investigate the presence of microparasites in fish Archosargus probatocephalus in a river near Maceió, Brazil. Light microscope observations of fragments of gill showed the presence of small cysts containing numerous myxospores that were morphologically identified as Henneguya. Transmission electron microscopy observations further revealed several gill cells containing groups of prokaryotic cells within large cytoplasmic vacuoles. Each infected host cell displayed a single vacuole containing a variable number of Rickettsia-like cells (up to 11), some of which presented the dumbbell shape characteristic of binary fission. The Rickettsia-like cells were pleomorphic, without a nucleus and with chromatin dispersed in the cytoplasm. They had a thin electron-dense wall of Gram-negative type. The morphology of these prokaryotic was similar to those of the order Rickettsiales and was described as a Rickettsia-like organism. Histopathological evaluation showed that several vacuole membranes had a lysed appearance. Some had ruptured, thus allowing direct contact between the Rickettsia-like organism and the cytoplasm of the host cell. The rupturing of the branchial epithelium may have contributed towards reduction of the surface area of the gills, but it is not possible to say that this was the cause of the host's death.

Ultrastructure of intracytoplasmic Rickettsia-like infection of the gills of the teleost Archosargus probatocephalus (Sparidae) in northeastern Brazil / Ultraestrutura de Rickettsia intracitoplasmática infectando as brânquias do teleósteo Archosargus probatocephalus (Sparidae) no Nordeste do Brasil

Abstract A histopathological survey was conducted to investigate the presence of microparasites in fish Archosargus probatocephalus in a river near Maceió, Brazil. Light microscope observations of fragments of gill showed the presence of small cysts containing numerous myxospores that were morphologically identified as Henneguya. Transmission electron microscopy observations further revealed several gill cells containing groups of prokaryotic cells within large cytoplasmic vacuoles. Each infected host cell displayed a single vacuole containing a variable number of Rickettsia-like cells (up to 11), some of which presented the dumbbell shape characteristic of binary fission. The Rickettsia-like cells were pleomorphic, without a nucleus and with chromatin dispersed in the cytoplasm. They had a thin electron-dense wall of Gram-negative type. The morphology of these prokaryotic was similar to those of the order Rickettsiales and was described as a Rickettsia-like organism. Histopathological evaluation showed that several vacuole membranes had a lysed appearance. Some had ruptured, thus allowing direct contact between the Rickettsia-like organism and the cytoplasm of the host cell. The rupturing of the branchial epithelium may have contributed towards reduction of the surface area of the gills, but it is not possible to say that this was the cause of the host's death.

Resumo Um levantamento histopatológico foi realizado para pesquisar a presença de microparasitas, no peixe Archosargus probatocephalus, em um rio próximo a Maceió, Brasil. Observações ao microscópio óptico de fragmentos de brânquias mostraram a presença de pequenos cistos contendo numerosos mixósporos, identificados morfologicamente como Henneguya. Ocasionalmente, na microscopia eletrônica de transmissão, foram observados vários corpos citoplasmáticos de inclusão, grupo aparentemente de células procarióticas que vivem dentro de um grande vacúolo citoplasmático de algumas células branquiais. As células hospedeiras infectadas tinham um único vacúolo contendo um número variável de células do tipo Rickettsia, até 11, algumas das quais em forma do haltere, característica da fissão binária. Essas células eram pleomórficas sem núcleo, tendo a cromatina dispersa no citoplasma e possuíam uma parede densa de elétrons finos do tipo Gram-negativo. A morfologia dessas células procarióticas foi semelhante àquelas da ordem Rickettsiales e foram descritas como organismos tipo Rickettsiae. A histopatologia mostra várias membranas de vacúolos circundantes com aspetos lisados, enquanto outras apresentam rupturas que mostram contato direto do organismos tipo Rickettsiae com o citoplasma da célula hospedeira. A ruptura do epitélio branquial pode ter contribuído para a redução da superfície das brânquias, mas não é possível afirmar que foi a causa da morte do hospedeiro.

Cellulitis of the face associated with SENLAT caused by Rickettsia slovaca detected by qPCR on scalp eschar swab sample: An unusual case report and review of literature.

BACKGROUND: Tick-borne rickettsioses are infectious diseases caused by obligate intracellular Gram-negative bacteria belonging to the spotted fever groupof Rickettsia. METHODS: We describe an unusual case of SENLAT (Scalp eschar and neck lymphadenopathy after tick bite), caused byRickettsia slovaca, associated with a cellulitis of the face in a 70-year-old woman, and diagnosed using qPCR on a scalp eschar swab. We review the literature regarding cases of SENLAT-associated-cellulitis and case of SENLAT diagnosed by qPCR on scalp eschar swabs. RESULTS: We found only one previous report of SENLAT associated with a cellulitis of the face. It was a nine-year-old French girl diagnosed by seroconversion for Rickettsia sp. Our review of the literature showed that qPCR on eschar swab samples is a less invasive method than performing cutaneous biopsy of the eschar and has good sensitivity and specificity (90% and 100%, respectively). CONCLUSIONS: We report the second case of cellulitis of the face associated with the SENLAT syndrome. Detection of Rickettsia by qPCR on swab sample of the scalp eschar is a simple, noninvasive technique allowing rapid diagnosis and treatment when SENLAT is suspected.

Rickettsia infection could be the missing piece of the Buerger's disease puzzle.

BACKGROUND: Rickettsia was suggested as a possible etiology of Buerger's disease (BD) in the 1980s but this suggestion was never ruled out or proven. Recently, we found evidence of Rickettsia by polymerase chain reaction in 3 out of 25 biopsy samples from the amputated limb of a young man diagnosed with BD. The aim of this paper was to investigate the presence of anti-rickettsial antibodies in the sera of BD patients. METHODS: To detect the IgG class antibody against Rickettsia rickettsii, which has cross reactions with the spotted fever group (RSFG), and Rickettsia typhi, which has cross reactions with typhus fever group, the sera of patients and controls were diluted to 1:64 and analyzed by indirect micro fluorescence immunoassay (MIF). RESULTS: The MIF study showed that 26 of the 28 patients were positive for Rickettsia rickettsii antibodies and MIF had the same appearance as the positive control, which was provided with the kit. In all members of the healthy control group, Rickettsia rickettsii was negative and had the appearance of the negative control. Rickettsia typhi was negative for all patients and members of the control group. CONCLUSIONS: A species of Rickettsia associated with the RSFG, which might not be pathogenic for the entire population, may induce BD in the context of a specific genetic or environmental background. RSFG infection could explain key questions about BD, including its gender and geographical distribution, clinical manifestation, angiography pattern, and pathological findings. Evaluating antibodies against RSFG in BD patients from different countries is now highly recommended.

[Rickettsiosis - Early skin biopsy is essential because of latency in serological findings]. / Rickettsiose.

BACKGROUND: Global travel increasis practitioner's confrontation with very special infectious diseases, like hemorrhagic viral diseases that are traditionally rare in European countries. Prompt diagnosis and subsequent induction of therapy are essential to prevent high rates of severe and lethal complications. ANAMNESIS: A 59-year-old man complained deterioration of general health after a 3-week vacation to South Africa. He presented fever and hemorrhagic erythema with pustula surrounded by necrotic margin on the right calf. COURSE AND THERAPY: On the second day of inpatient treatment, a papulovesiculous, partly hemorrhagic exanthema appeared. With a tentative diagnosis of Rickettsiosis, we performed specific diagnostics by serology and biopsy. Therapy was initiated with doxycycline (200 mg/d) for 7 days. Under this regimen clinical symptoms healed without consequences. Rickettsioses are ubiquitious zoonoses that are caused by various Rickettsia subtypes. The stay in endemic regions together with signs of fever, reduced general health, eschar and exanthema are suspicious for this disease. Therapy should be initiated immediately in cases of clinical suspicion with a characteristic case history. The seroconversion, which appears later in course, should not give reason for avoiding early skin biopsy due to the potentially fatal course of the disease. Biopsy enables early histological proof of a dermal vasculitic inflammation pattern and PCR analysis before subsequent serological controls and proofs.

Cutaneous manifestations of spotted fever rickettsial infections in the Central Province of Sri Lanka: a descriptive study.

BACKGROUND: Characteristic skin lesions play a key role in clinical diagnosis of spotted fever group rickettsioses and this study describes these cutaneous manifestations along with basic histological features. METHODS AND FINDINGS: Study was conducted at Medical Unit, Teaching Hospital, Peradeniya, from November 2009 to October 2011, where a prospective data base of all rickettsial infections is maintained. Confirmation of diagnosis was made when IgM and IgG immunofluorescent antibody titre of 1/32 and >1/256 respectively. Of the 210 clinical cases, 134 had cutoff antibody titers for Rickettsia conorii antigen for confirmation. All these 134 patients had fever and skin rash, and of them 132(98%) had discrete maculopapular rash while eight (6%) had fern leaf type skin necrosis. Eight patients (6%) had healed tick bite marks. Average size of a skin lesion was 5 mm and rash involved 52% of body surface, distributed mainly in limbs and back of the chest. Generally the facial and leg skin was slightly oedematous particularly in old aged patients. Sixteen patients (12%) had pain and swelling of ankle joints where swelling extended to feet and leg. Biopsies from skin rash of six patients showed evidence of cutaneous vasculitis and of them, 247 bp region of the 17-kDa spotted fever group specific protein antigen was amplified using PCR. CONCLUSIONS: A discrete maculopapular rash and occasional variations such as fern leaf shape necrosis and arthritis are found in spotted fever group. Histology found vasculitis as the pathology of these lesions.

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.

Significantly higher cytokine and chemokine levels in patients with Japanese spotted fever than in those with Tsutsugamushi disease.

Tetracyclines are administered to cure Japanese spotted fever (JSF) and tsutsugamushi disease (TD). It is generally said that the clinical course of JSF is worse than that of TD despite antibiotic treatment. The precise mechanism underlying the more severe clinical course of JSF is not fully understood. We therefore examined whether the differential cytokine profile between these two infectious diseases contributes to the difference in clinical severity. The serum concentrations of various cytokines (tumor necrosis factor alpha [TNF-α], interleukin-6 [IL-6], and gamma interferon [IFN-γ]) and chemokines (IL-8, interferon-inducible protein 10 [IP-10], monocyte chemoattractant protein 1 [MCP-1], macrophage inflammatory protein 1α [MIP-1α], MIP-1ß, and eotaxin) were measured in 32 TD and 21 JSF patients. The results showed that serum levels of TNF-α in the acute phases of TD and JSF were significantly increased, with a higher concentration of TNF-α in patients with JSF (mean, 39.9 pg/ml) than in those with TD (mean, 13.8 pg/ml). Comparatively higher levels of other cytokines and chemokines (IL-6, IFN-γ, IL-8, IP-10, MCP-1, MIP-1α, and MIP-1ß) were also observed in the acute phase of JSF. The clinical severity score (3.67 ± 1.71) of JSF patients was higher than that of TD patients (1.47 ± 0.77). Our findings revealed that the cytokine and chemokine levels in the acute phase of JSF were significantly higher than those in the acute phase of TD. The differential cytokine levels may be related to the difference in clinical severity between JSF and TD.

[Update on SENLAT syndrome: scalp eschar and neck lymph adenopathy after a tick bite]. / Les nouveautés sur le syndrome SENLAT : Scalp Eschar and Neck LymphAdenopathy after Tick bite.

SENLAT syndrome, also known as TIBOLA/DEBONEL, is an emerging disease in France. The major symptoms are necrotic eschar on the scalp associated with painful cervical lymphadenopathy. It occurs mainly in women and children during the cold seasons after a bite by a Dermacentor tick, responsible for transmitting Rickettsia slovaca or Rickettsia raoultii. Cutaneous swabs are safe, easy and reliable tools that should be used routinely by physicians to confirm diagnosis. In this particular disease, they should be preferred to serology, which is less sensitive. Doxycycline is the antibiotic of choice for this syndrome.

Exploratory study on pathogenesis of far-eastern spotted fever.

Far-eastern spotted fever is an emerging disease caused by Rickettsia heilongjiangensis, a tick-borne obligate intracellular bacterium. In this study, R. heilongjiangensis was used to infect BALB/c mice by inoculation of retro-orbital venous plexus to imitate a blood infection caused by tick biting. We found that R. heilongjiangensis rapidly entered the circulation for systemic dissemination and the pathogen existed in liver, spleen, lungs, and brain of the mice at least 9 days post-infection (p.i.). Severe pathological lesions were observed in liver, lungs, and brain at Day 6 p.i. In addition, the elevated levels of inflammatory cytokines, including interferon-γ, tumor necrosis factor, and CC chemokine, were detected in the infected organs at Day 3 p.i. Our results reveal that R. heilongjiangensis may cause an infection in BALB/c mice and the pathological lesions in the infected mice are associated with host inflammatory response induced by R. heilongjiangensis.

A patient from Argentina infected with Rickettsia massiliae.

The first confirmed case of Rickettsia massiliae infection in the New World (Buenos Aires, Argentina) is described. To date, only two cases of human infection had been reported in Europe. The patient, a woman, had a fever, a palpable purpuric rash on the upper and lower extremities, and a skin lesion (eschar) on the right leg compatible with tache noire. When interviewed, she reported having had contact with dog ticks. After treatment with doxycycline for 12 days, her symptoms resolved. Rickettsia massiliae infection was diagnosed by molecular-based detection of the microorganism in a biopsy specimen of the eschar.

Tick-borne lymphadenopathy: a new infectious disease in children.

OBJECTIVE: To describe the epidemiologic and clinical aspects of patients with tick-borne lymphadenopathy (TIBOLA). PATIENTS AND METHODS: The study included all patients treated in our hospital who presented characteristic clinical signs of TIBOLA consisting in the presence of an inoculation lesion after a tick bite with regional lymphadenopathies. The study was carried out at the "Corporació Parc Taulí" hospital in the city of Sabadell, Barcelona, Spain. The inclusion period was from April 2000 to April 2006. Serology tests were performed for Rickettsia conorii, R. slovaca, and Borrelia burgdorferi. The presence of Rickettsia was assessed by means of polymerase chain reaction (PCR)-restriction fragment length polymorphism (PCR-RFLP) and linear-after-the exponential-PCR in blood, skin biopsy, and ticks from the patients. RESULTS: Thirty-six patients fulfilled the inclusion criteria. Twenty-eight patients were children. In most cases, infection occurred between the months of October and April. In 34 patients the tick bite was on the scalp. A necrotic eschar surrounded by a perilesional erythematous halo was observed in 29 cases. All patients had painful regional lymphadenopathies. Serology for R. conorii was positive in 8 cases and for R. slovaca in 2. PCR was negative. The tick, identified as Dermacentor marginatus, was studied in 7 patients. Four of the 7 D. marginatus were positive for sequences compatible with R. slovoca as determined by RFLP or DNA sequencing. Thirty-three patients received antibiotic treatment. Progress was satisfactory in all cases. CONCLUSIONS: TIBOLA is present in Catalonia (Northeastern Spain) mainly in children. Although clinical and epidemiologic manifestations are very specific microbiologic confirmation is difficult.

Prospective evaluation of rickettsioses in the Trakya (European) region of Turkey and atypic presentations of Rickettsia conorii.

In 2004 between the months of May-November, 11 patients with spotted fever group (SFG) rickettsioses were admitted to the Trakya University Hospital in Edirne, Turkey. SFG rickettsioses were diagnosed clinically. Before treatment, punch biopsy from skin lesions, especially from the eschar, was performed. Serum specimens were tested by IFA using a panel of nine rickettsial antigens, including SFG rickettsiae and R. typhi. Western blotting and standard PCR were also performed. The average age of the 11 patients (4 male and 7 female) was 51 years. All the patients had high fever; 10 (91%) had maculopapular rash; 8 (73%) had rash in the palms or on the soles. Five patients had a unique eschar; two had double eschars (64%). Two patients presented with multiple organ failure and one of them died. All the patients had significant antibody titers against SFG rickettsiae. PCR experiments of skin biopsies were positive in six (60%) of 10 skin biopsy samples and DNA sequencing of the positive PCR products gave 100% homology with Rickettsia conorii Malish 7 for opmA and gltA. Trakya Region in an endemic area for rickettsioses. In this series, three patients presented with life-threatening diseases and one of them died. This patient was the first fatal case (2.8%). Atypic and serous life-threatening presentations of rickettsioses must be kept in mind for the differential diagnosis of febrile disease in Turkey.

Histologic features and immunodetection of African tick-bite fever eschar.

African tick-bite fever (ATBF) is a rickettsiosis caused by Rickettsia africae. We describe histologic features and immunodetection of R. africae in cutaneous inoculation eschars from 8 patients with ATBF, which was diagnosed by culture or association of positive PCR detection and positive serologic results. We used quantitative image analysis to compare the pattern of inflammation of these eschars with those from Mediterranean spotted fever. We evaluated the diagnostic value of immunohistochemical techniques by using a monoclonal antibody to R. africae. ATBF eschars were histologically characterized by inflammation of vessels composed mainly of significantly more polymorphonuclear leukocytes than are found in cases of Mediterranean spotted fever (p < 0.05). Small amounts R. africae antigens were demonstrated by immunohistochemical examination in 6 of 8 patients with ATBF. Neutrophils in ATBF are a notable component of the host reaction, perhaps because ATBF is a milder disease than the other rickettsioses. Immunohistochemical detection of rickettsial antigens may be useful in diagnosing ATBF.

African tick bite fever: a not-so-uncommon illness in international travelers.

BACKGROUND: African tick bite fever is a rickettsial illness that has recently emerged as a significant disease among international travelers. The vector is the Amblyomma tick, which is endemic to sub-Saharan Africa and parts of the eastern Caribbean. OBSERVATIONS: We describe a middle-aged woman who returned from a mission trip to Zimbabwe with an influenzalike illness and inoculation eschar; she also had a history of travel to a game farm. Biopsy revealed a histopathologic pattern consistent with an infectious pathogenesis. Immunohistochemical staining confirmed the presence of rickettsial organisms. In light of the patient's history, the clinical constellation of signs and symptoms, and the results of ancillary laboratory testing, a diagnosis of African tick bite fever was made. The patient was treated with doxycycline hydrochloride and had an uncomplicated course. CONCLUSIONS: This report further highlights the epidemiological and clinical features of African tick bite fever. With the increase in international travel, it is important to recognize the illness in those who have been to endemic countries and to counsel patients regarding preventive measures for planned travel.

Astrakhan scrub typhus: time course of infectious process according to electron microscopy findings.

Structural changes in the liver and spleen of albino mice with Astrakhan scrub typhus were studied by electron microscopy. Rickettsia invasion and formation of granulomas induced structural (destructive) and metabolic changes in hepatocytes. Rickettsia were degraded in cytophagosomes and cytolysophagosomes of hepatic macrophages (Kupffer cells) and blood capillary endotheliocytes. In the spleen rickettsia were seen in the extracellular spaces and in various cell populations.

Tick-borne typhus fever of northern Asia: some characteristics of the pathogenesis.

Morphological changes in the viscera of albino mice were studied over the course of North Asia typhus fever. In general, the microcirculatory bed in the studied organs (brain, liver, spleen, peritoneum, and testicle) corresponded to angioparalytical capillary and venular hyperemia. Macrophagic reaction (proliferation of stellate macrophages) transformed into granulomatous reaction in the course of the experiment. Macrophagic reaction of the spleen was characterized by blurred follicular pattern. In the testes a tendency to the loss of normal spermatogenesis was observed.