Frecuencia de anticuerpos y seroconversión frente a Rickettsia spp. en pacientes atendidos en instituciones de salud del departamento de Caldas, Colombia, 2016-2019 / Frequency of antibodies and seroconversion against Rickettsia spp in patients consulting health institutions in the department of Caldas, Colombia, 2016-2019

Resumen | Introducción. Las rickettsiosis son enfermedades zoonóticas transmitidas por artrópodos que cumplen el papel de vectores y reservorios, y cuyos síntomas son inespecíficos, por lo que su diagnóstico clínico es difícil. La inmunofluorescencia indirecta (IFI) es el método de referencia para el diagnóstico. En Colombia, ha resurgido el interés por su estudio por los casos de rickettsiosis detectados en el norte del departamento de Caldas a partir del 2001. Objetivo. Establecer la frecuencia de anticuerpos y la seroconversión contra Rickettsia spp. en pacientes atendidos en instituciones de salud del departamento de Caldas, Colombia, entre 2016 y 2019. Materiales y métodos. Se hizo un estudio de diseño cuantitativo, observacional y descriptivo, con una muestra no probabilística de 175 pacientes atendidos en diferentes municipios de Caldas, a quienes se les realizó IFI para la detección de anticuerpos en fase aguda y convaleciente contra Rickettsia rickettsii, R. typhi y R. felis. Resultados. El promedio de edad de los pacientes fue de 31 años. Los municipios con mayor proporción de seropositivos fueron Belalcázar, Chinchiná, Filadelfia, La Dorada, La Merced y Manizales. El 66 % tenía mascotas y el 12 % reportó picaduras por artrópodos. Los signos y síntomas más frecuentes fueron cefalea (69,7 %), artromialgia (60 %), y fiebre (58,2 %). La seroprevalencia por IgG fue de 60 % para R. rickettsii, 47,9 % para R. typhi y 24 % para R. felis. Ocho pacientes presentaron seroconversión. Conclusión. Se encontró evidencia de la circulación de rickettsias del grupo de las fiebres manchadas y del grupo del tifus asociada con casos humanos en el departamento de Caldas.

Abstract | Introduction: Rickettsioses are zoonotic diseases transmitted by arthropods acting as vectors and reservoirs. Disease symptoms are nonspecific and, therefore, their clinical diagnosis is difficult. Indirect immunofluorescence (IFA) is the gold standard assay for diagnosis. The interest for conducting studies on these pathologies has resurfaced in Colombia since 2001; besides, previous studies have evidenced cases of rickettsiosis in the north of the department of Caldas. Objective: To establish the frequency of antibodies and seroconversion against Rickettsia spp. In patients consulting health institutions in Caldas, Colombia, from 2016 to 2019. Materials and methods: We conducted a quantitative, observational, and descriptive study on a non-probabilistic sample of 175 patients with symptoms compatible with rickettsiosis who consulted in different municipalities of Caldas, Colombia; IFA was performed to detect antibodies in the acute and convalescent phases against Rickettsia rickettsii, Rickettsia typhi, and Rickettsia felis. Results: The average age of the patients was 31 years. The municipalities with the highest proportion of seropositive cases were Belalcázar, Chinchiná, Filadelfia, La Dorada, La Merced, and Manizales; 66% of patients owned pets and 12% reported arthropod bites. The most frequent signs and symptoms were headache (69.7%), arthromyalgia (60%), and fever (58.2%). IgG seroprevalence was 60% for R. rickettsii, 47.9% for R. typhi, and, and 24% for R. felis. Eight patients presented seroconversion. Conclusion: We found evidence of the circulation of Rickettsia species from the spotted fever group and the typhus group associated with human cases in Caldas.

Murine Typhus Presenting With Mucosal Involvement.

Lipschutz ulcers (LU) present as painful genital ulcers in nonsexually active females. Associated infections include Epstein Barr virus, Mycoplasma pneumoniae, Cytomegalovirus, and influenza. To our knowledge, this is the first report of LU occurring with murine typhus. Murine typhus is caused by Rickettsia typhi, a Gram-negative, obligate intracellular organism. Rat fleas (Xenopsylla cheopis) are the classic vector, although cat fleas (Ctenocephalides felis) found on cats, dogs, and opossums have been implicated in maintaining the life cycle of R. typhi in suburban areas. Murine typhus can have a nonspecific presentation making a strong index of suspicion crucial to its diagnosis. The most common presenting signs include fever, poor appetite, malaise, and headache. Laboratory abnormalities may include elevated C-reactive protein, elevated erythrocyte sedimentation rate, hypoalbuminemia, elevated transaminases, elevated neutrophil band count, and thrombocytopenia. The treatment of choice for R. typhi is doxycycline.

Fatal murine typhus with hemophagocytic lymphohistiocytosis in a child.

Hemophagocytic lymphohistiocytosis is a rare complication in Rickettsia typhi infections. We report the case of a 2-year-old boy with sudden night-onset fever, pallor, neck adenopathy and erythematous macular rash on the thorax, thighs and buttocks. During admission, he developed hyponatremia, hypoalbuminemia, anemia, thrombocytopenia, leukopenia, neutropenia, liver damage, hemorrhages and persistent fever. No hematological improvement was observed after the initial management, neoplastic diseases were discarded by bone marrow aspiration and lymph node biopsy; hemophagocytic lymphohistiocytosis was diagnosed. By immunohistochemistry and indirect immunofluorescence, murine typhus was also diagnosed and doxycycline was started with transitory recovery. Later, the child developed kidney failure and distributive shock that evolved to cardiac arrest and death. This is the first case report in Mexico on a fatal murine typhus associated with hemophagocytic lymphohistiocytosis in which the etiology was evidenced by histopathology.

Detección de Rickettsia typhi en Rhipicephalus sanguineus s.l. y Amblyomma mixtum en el sur de México / Detection of Rickettsia typhi in Rhipicephalus sanguineus s.l. and Amblyomma mixtum in South Mexico

Resumen: Objetivo: Determinar la presencia de Rickettsia typhi en Rhipicephalus sanguineus s.l. y Amblyomma mixtum, en el sur de México. Material y métodos: Las garrapatas fueron colectadas en humanos y animales domésticos. Se determinó la presencia de Rickettsia por reacción en cadena de la polimerasa (PCR, por sus siglas en inglés) y secuenciación. Resultados: 10/39 viales de trabajo amplificaron fragmentos de los genes gltA, htrA y ompB, en 7/10 proveniente de Rh. sanguineus s.l. colectadas de perros y en 3/10 de A. mixtum colectadas de caballo y humano. La secuenciación indicó R. typhi en Rh. sanguineus y A. mixtum con homología de 100% (LS992663.1), para una región del gen de htrA, y de 99% (LS992663.1), con las regiones de los genes de gltA y OmpB. La tasa mínima de infección (TMI) para R. typhi fue de 3.88. Conclusiones: Las garrapatas Rhipicephalus sanguineus s.l. y Amblyomma mixtum están infectadas naturalmente con R. typhi en el sur de México.

Abstract: Objective: To determine the presence of Rickettsia typhi in Rhipicephalus sanguineuss.l. and Amblyomma mixtum in southern Mexico. Materials and methods: Ticks were collected in humans and domestic animals. The presence of Rickettsia was determined by PCR and sequencing. Results: 10/39 work vials amplified fragments of the gltA,htrA and ompB genes. On 7/10 from Rh. sanguineus s.l collected from dogs and in 3/10 of A. mixtum collected from horse and human. Sequencing indicated R. typhi in Rh. Sanguineus and A. mixtum with 100% homology (LS992663.1) for a region of the htrA gene and 99% (LS992663.1) with the regions of the gltA and OmpB genes. The minimum infection rate (TMI) for R. typhi was 3.88. Conclusions: Rhipicephalus sanguineuss.l. and Amblyomma mixtum are naturally infected with R. typhi in Southern Mexico.

Serum C-reactive protein and procalcitonin values in acute Q fever, scrub typhus, and murine typhus.

BACKGROUND: Although C-reactive protein (CRP) and procalcitonin (PCT) are widely used inflammatory markers for infectious diseases, their role and potential application for rickettsioses were rarely studied. METHODS: A retrospective chart review and serological study were conducted in patients with rickettsioses. The clinical presentations, characteristics, laboratory data, and treatment responses were recorded and their associations with CRP and PCT values were analyzed. RESULTS: A total of 189 cases of rickettsioses, including 115 cases of acute Q fever (60.8%), 55 cases of scrub typhus (29.1%), and 19 cases of murine typhus (10.1%) were investigated. Both CRP and PCT values increased in the acute phase and declined in the convalescent phase. In the acute phase, mean CRP and PCT values were 78.2 ± 63.7 mg/L and 1.05 ± 1.40 ng/mL, respectively. Percentages of patients falling under different cut-off values of CRP and PCT were calculated systematically. Only 10.8% of CRP was > 150 mg/L and 14.2% of PCT was > 2.0 ng/mL. Patients with delayed responses to doxycycline treatment (> 3 days from treatment to defervescence) had significantly higher CRP values (102.7 ± 77.1 vs. 72.2 ± 58.2 mg/L, p = 0.041) and more PCT > 1.0 ng/ml (48.4% vs. 26.0%, p = 0.019) in the acute phase; higher CRP values (19.1 ± 37.4 vs. 3.6 ± 13.1 mg/L, p = 0.049) and more PCT > 0.5 ng/ml (19.2% vs. 1.4%, p = 0.005) in the convalescent phase. Correlation analysis was conducted for patients with acute Q fever. CRP and PCT values were positively correlated to each other, and both markers also had a positive correlation with serum aspartate transaminase values. Both CRP and PCT values and white blood cell counts were positively correlated to the days needed from doxycycline treatment to defervescence. CONCLUSION: CRP and PCT values might be useful in clinical investigations for patients with suspected rickettsioses and in predicting the response to doxycycline treatment for rickettsioses.

First description of a clinical case of murine typhus in Campeche, Mexico

Abstract Murine typhus is a flea-borne disease caused by Rickettsia typhi, which was first detected in Mexico in 1927. It was not until 1996 that the first systematized study involving this pathogen was conducted in two coastal states of Mexico. We now report the first confirmed case of murine typhus in the state of Campeche, which occurred in a male patient who exhibited fever, thrombocytopenia, hyperbilirubinemia, and a rash. Furthermore, the patient reported having had previous contact with Rickettsia reservoirs.

The Cat Flea (Ctenocephalides felis) Immune Deficiency Signaling Pathway Regulates Rickettsia typhi Infection.

Rickettsia species are obligate intracellular bacteria with both conserved and lineage-specific strategies for invading and surviving within eukaryotic cells. One variable component of Rickettsia biology involves arthropod vectors: for instance, typhus group rickettsiae are principally vectored by insects (i.e., lice and fleas), whereas spotted fever group rickettsiae are exclusively vectored by ticks. For flea-borne Rickettsia typhi, the etiological agent of murine typhus, research on vertebrate host biology is facilitated using cell lines and animal models. However, due to the lack of any stable flea cell line or a published flea genome sequence, little is known regarding R. typhi biology in flea vectors that, importantly, do not suffer lethality due to R. typhi infection. To address if fleas combat rickettsial infection, we characterized the cat flea (Ctenocephalides felis) innate immune response to R. typhi Initially, we determined that R. typhi infects Drosophila cells and increases antimicrobial peptide (AMP) gene expression, indicating immune pathway activation. While bioinformatics analysis of the C. felis transcriptome identified homologs to all of the Drosophila immune deficiency (IMD) and Toll pathway components, an AMP gene expression profile in Drosophila cells indicated IMD pathway activation upon rickettsial infection. Accordingly, we assessed R. typhi-mediated flea IMD pathway activation in vivo using small interfering RNA (siRNA)-mediated knockdown. Knockdown of Relish and Imd increased R. typhi infection levels, implicating the IMD pathway as a critical regulator of R. typhi burden in C. felis These data suggest that targeting the IMD pathway could minimize the spread of R. typhi, and potentially other human pathogens, vectored by fleas.

Respuesta a la carta de Faccini et al / Reply to Faccini et al

Sr. Editor, Agradecemos los aportes en relación con nuestra publicación. El objetivo del artículo "Enfoque clínico del síndrome febril agudo en Colombia" fue el de considerar los posibles diagnósticos etiológicos que se enmarquen dentro de la definición de la duración de la fiebre en el tiempo, definiendo como aguda aquella que tiene una duración de hasta 7 días. Sin embargo, el cuadro de Chagas agudo incluye en su definición de caso probable "Fiebre continua o prolongada mayor de 7 días, acompañado o no de alguno de los siguientes síntomas. . .". Este criterio ha sido utilizado en los estudios de brotes referenciados en Colombia. Por esta razón, no fue incluido como parte de la revisión

Mr. Editor, We appreciate the contributions in relation to our publication. The aim of the article "Clinical approach to acute febrile syndrome in Colombia" was to consider the possible etiological diagnoses that fall within the definition of the duration of fever over time, defining as acute that which has a duration of up to 7 days. However, acute Chagas disease includes in its probable case definition "Continuous or prolonged fever greater than 7 days, accompanied or not by any of the following symptoms . . .". This criterion has been used in outbreak studies referenced in Colombia. For this reason, it was not included as part of the review.

GFPuv-Expressing Recombinant Rickettsia typhi: a Useful Tool for the Study of Pathogenesis and CD8+ T Cell Immunology in R. typhi Infection.

Rickettsia typhi is the causative agent of endemic typhus, a disease with increasing incidence worldwide that can be fatal. Because of its obligate intracellular life style, genetic manipulation of the pathogen is difficult. Nonetheless, in recent years, genetic manipulation tools have been successfully applied to rickettsiae. We describe here for the first time the transformation of R. typhi with the pRAM18dRGA plasmid that originally derives from Rickettsia amblyommatis and encodes the expression of GFPuv (green fluorescent protein with maximal fluorescence when excited by UV light). Transformed R. typhi (R. typhiGFPuv) bacteria are viable, replicate with kinetics similar to those of wild-type R. typhi in cell culture, and stably maintain the plasmid and GFPuv expression under antibiotic treatment in vitro and in vivo during infection of mice. CB17 SCID mice infected with R. typhiGFPuv succumb to the infection with kinetics similar to those for animals infected with wild-type R. typhi and develop comparable pathology and bacterial loads in the organs, demonstrating that the plasmid does not influence pathogenicity. In the spleen and liver of infected CB17 SCID mice, the bacteria are detectable by immunofluorescence microscopy in neutrophils and macrophages by histological staining. Finally, we show for the first time that transformed rickettsiae can be used for the detection of CD8+ T cell responses. GFP-specific restimulation of spleen cells from R. typhiGFPuv-infected BALB/c mice elicits gamma interferon (IFN-γ), tumor necrosis factor alpha (TNF-α), and interleukin 2 (IL-2) secretion by CD8+ T cells. Thus, R. typhiGFPuv bacteria are a novel, potent tool to study infection with the pathogen in vitro and in vivo and the immune response to these bacteria.

CD4+ T Cells Are as Protective as CD8+ T Cells against Rickettsia typhi Infection by Activating Macrophage Bactericidal Activity.

Rickettsia typhi is an intracellular bacterium that causes endemic typhus, a febrile disease that can be fatal due to complications including pneumonia, hepatitis and meningoencephalitis, the latter being a regular outcome in T and B cell-deficient C57BL/6 RAG1-/- mice upon Rickettsia typhi infection. Here, we show that CD4+ TH1 cells that are generated in C57BL/6 mice upon R. typhi infection are as protective as cytotoxic CD8+ T cells. CD4+- as well as CD8+-deficient C57BL/6 survived the infection without showing symptoms of disease at any point in time. Moreover, adoptively transferred CD8+ and CD4+ immune T cells entered the CNS of C57BL/6 RAG1-/- mice with advanced infection and both eradicated the bacteria. However, immune CD4+ T cells protected only approximately 60% of the animals from death. They induced the expression of iNOS in infiltrating macrophages as well as in resident microglia in the CNS which can contribute to bacterial killing but also accelerate pathology. In vitro immune CD4+ T cells inhibited bacterial growth in infected macrophages which was in part mediated by the release of IFNγ. Collectively, our data demonstrate that CD4+ T cells are as protective as CD8+ T cells against R. typhi, provided that CD4+ TH1 effector cells are present in time to support bactericidal activity of phagocytes via the release of IFNγ and other factors. With regard to vaccination against TG Rickettsiae, our findings suggest that the induction of CD4+ TH1 effector cells is sufficient for protection.

Liver Necrosis and Lethal Systemic Inflammation in a Murine Model of Rickettsia typhi Infection: Role of Neutrophils, Macrophages and NK Cells.

Rickettsia (R.) typhi is the causative agent of endemic typhus, an emerging febrile disease that is associated with complications such as pneumonia, encephalitis and liver dysfunction. To elucidate how innate immune mechanisms contribute to defense and pathology we here analyzed R. typhi infection of CB17 SCID mice that are congenic to BALB/c mice but lack adaptive immunity. CB17 SCID mice succumbed to R. typhi infection within 21 days and showed high bacterial load in spleen, brain, lung, and liver. Most evident pathological changes in R. typhi-infected CB17 SCID mice were massive liver necrosis and splenomegaly due to the disproportionate accumulation of neutrophils and macrophages (MΦ). Both neutrophils and MΦ infiltrated the liver and harbored R. typhi. Both cell populations expressed iNOS and produced reactive oxygen species (ROS) and, thus, exhibited an inflammatory and bactericidal phenotype. Surprisingly, depletion of neutrophils completely prevented liver necrosis but neither altered bacterial load nor protected CB17 SCID mice from death. Furthermore, the absence of neutrophils had no impact on the overwhelming systemic inflammatory response in these mice. This response was predominantly driven by activated MΦ and NK cells both of which expressed IFNγ and is considered as the reason of death. Finally, we observed that iNOS expression by MΦ and neutrophils did not correlate with R. typhi uptake in vivo. Moreover, we demonstrate that MΦ hardly respond to R. typhi in vitro. These findings indicate that R. typhi enters MΦ and also neutrophils unrecognized and that activation of these cells is mediated by other mechanisms in the context of tissue damage in vivo.

Structural Insights into Substrate Recognition and Catalysis in Outer Membrane Protein B (OmpB) by Protein-lysine Methyltransferases from Rickettsia.

Rickettsia belong to a family of Gram-negative obligate intracellular infectious bacteria that are the causative agents of typhus and spotted fever. Outer membrane protein B (OmpB) occurs in all rickettsial species, serves as a protective envelope, mediates host cell adhesion and invasion, and is a major immunodominant antigen. OmpBs from virulent strains contain multiple trimethylated lysine residues, whereas the avirulent strain contains mainly monomethyllysine. Two protein-lysine methyltransferases (PKMTs) that catalyze methylation of recombinant OmpB at multiple sites with varying sequences have been identified and overexpressed. PKMT1 catalyzes predominantly monomethylation, whereas PKMT2 catalyzes mainly trimethylation. Rickettsial PKMT1 and PKMT2 are unusual in that their primary substrate appears to be limited to OmpB, and both are capable of methylating multiple lysyl residues with broad sequence specificity. Here we report the crystal structures of PKMT1 from Rickettsia prowazekii and PKMT2 from Rickettsia typhi, both the apo form and in complex with its cofactor S-adenosylmethionine or S-adenosylhomocysteine. The structure of PKMT1 in complex with S-adenosylhomocysteine is solved to a resolution of 1.9 Å. Both enzymes are dimeric with each monomer containing an S-adenosylmethionine binding domain with a core Rossmann fold, a dimerization domain, a middle domain, a C-terminal domain, and a centrally located open cavity. Based on the crystal structures, residues involved in catalysis, cofactor binding, and substrate interactions were examined using site-directed mutagenesis followed by steady state kinetic analysis to ascertain their catalytic functions in solution. Together, our data reveal new structural and mechanistic insights into how rickettsial methyltransferases catalyze OmpB methylation.

Caso probable de tifus murino con falla ventilatoria en una adolescente del área urbana de Cali, Colombia / Probable case of murine typhus with respiratory failure in an adolescent from the urban area of Cali, Colombia

El tifus murino es una enfermedad infecciosa de carácter zoonótico causada por Rickettsia typhi . Se presenta el caso de una paciente femenina de 13 años edad, procedente del área urbana de la ciudad de Cali, quien presentó un cuadro febril asociado a taquipnea y exantema maculopapular generalizado en tronco y extremidades. Durante las primeras 48 h en la UCI pediátrica desarrolló rápido deterioro clínico, fiebre persistente, aumento de reactantes de fase aguda, presencia de infiltrados pulmonares intersticiales bilaterales y derrame pleural, requiriendo ventilación mecánica no invasiva. Se inició tratamiento con doxiciclina frente a la sospecha de una posible infección por agentes rickettsiales. Veinticuatro horas más tarde la paciente presentó mejoría clínica, resolución del exantema y retiro de la ventilación no invasiva. Por medio de la prueba de inmunofluorescencia indirecta se evidenciaron títulos de 1:512 frente al grupo del tifus, constatando el diagnóstico probable de tifus murino.

Murine typhus is a zoonotic infectious disease caused by Rickettsia typhi . We report a case of a 13-year old female patient from the urban area of the city of Cali, who presented with fever, associated with tachypnoea and generalised maculopapular exanthema on the trunk and limbs. During the first 48 h in the paediatric ICU, she rapidly deteriorated, with persistent fever, increased acute phase reactants, bilateral interstitial pulmonary infiltrates and pleural effusion requiring noninvasive ventilation. Treatment with doxycycline was initiated due to a suspected infection by rickettsial agents. Twenty-four hours later the patient presented clinical improvement and resolution of the exanthema, thus the non-invasive ventilation was withdrawn. By means of a indirect immunofluorescence test, titres of 1:512 were shown against the typhus group, leading to the probable diagnosis of murine typhus.

Detección molecular de Rickettsia typhi en perros de una comunidad rural de Yucatán, México / Molecular evidence of Rickettsia typhi infection in dogs from a rural community in Yucatán, México

Introducción. Rickettsia typhi es la bacteria causante del tifus múrido o endémico, el cual es transmitido al ser humano principalmente por medio de las heces infectadas de pulgas y en cuyo ciclo de infección se encuentran involucrados distintos animales sinantrópicos y domésticos. En la comunidad rural de Bolmay, Yucatán, México, se reportaron casos de tifus múrido en seres humanos durante el periodo 2007-2010. Objetivo. Identificar la presencia de R . typhi y estimar la frecuencia de infección en perros de Bolmay, México. Materiales y métodos. Se tomaron muestras de sangre completa de 128 perros, se les extrajo el ADN total y se analizaron mediante reacción en cadena de la polimerasa (PCR) para amplificar los fragmentos del gen de 17 kDa y omp B , y confirmar la presencia de Rickettsia spp. Los productos de las reacciones se enviaron a secuenciación y se les hizo un análisis de alineamiento con Basic Local Alignment Search Tool (BLAST). Resultados. Se encontró una frecuencia de infección de 5,5 % (7/128). El alineamiento demostró 99 % de homologación para el gen de 17 kDa y 100 % para el gen omp B en R . typhi . Conclusión. Se detectó la presencia de R . typhi pero una baja frecuencia de infección en perros de la comunidad de estudio; sin embargo, la especie podría representar un riesgo de transmisión para los seres humanos.

Introduction: Rickettsia typhi causes murine or endemic typhus, which is transmitted to humans primarily through flea bites contaminated with feces. Synanthropic and domestic animals also contribute to the infection cycle of R. typhi . Cases of murine typhus in humans were reported in the rural community of Bolmay, Yucatán, México, between 2007 and 2010. Objective: To identify the presence of R . typhi and estimate the frequency of infection in dogs from Bolmay, México, a locality with previous reports of murine typhus in humans. Materials and methods: Whole blood samples were taken from 128 dogs. Total DNA was extracted for use in the polymerase chain reaction (PCR) to amplify fragments of the 17 kDa and omp B genes and confirms the presence of Rickettsia spp. The reaction products were sequenced, and alignment analysis was performed using the BLAST tool. Results: The frequency of R. typhi infection in dogs was 5.5 % (7/128). The alignment identified 99% and 100% homology to the R . typhi 17 kDa and omp B genes, respectively. Conclusion: We confirmed the presence of R . typhi in dogs in the studied community but at a low frequency. However, there is potential risk of transmission to humans.

Rickettsia typhi IN RODENTS AND R. felis IN FLEAS IN YUCATÁN AS A POSSIBLE CAUSAL AGENT OF UNDEFINED FEBRILE CASES / Rickettsia typhi y R. felis en roedores y sus pulgas en Yucatán como posible agente causal de casos febriles indefinidos

Rickettsia typhi is the causal agent of murine typhus; a worldwide zoonotic and vector-borne infectious disease, commonly associated with the presence of domestic and wild rodents. Human cases of murine typhus in the state of Yucatán are frequent. However, there is no evidence of the presence of Rickettsia typhi in mammals or vectors in Yucatán. The presence of Rickettsia in rodents and their ectoparasites was evaluated in a small municipality of Yucatán using the conventional polymerase chain reaction technique and sequencing. The study only identified the presence of Rickettsia typhi in blood samples obtained from Rattus rattus and it reported, for the first time, the presence of R. felis in the flea Polygenis odiosus collected from Ototylomys phyllotis rodent. Additionally, Rickettsia felis was detected in the ectoparasite Ctenocephalides felis fleas parasitizing the wild rodent Peromyscus yucatanicus. This study’s results contributed to a better knowledge of Rickettsia epidemiology in Yucatán.

Rickettsia typhi es el agente causal del tifo murino; una enfermedad zoonótica transmitida por vector mundialmente distribuida, comúnmente asociada con la presencia de roedores domésticos y silvestres. Los casos humanos de tifo murino en el Estado de Yucatán son frecuentes. Sin embargo, no existe evidencia de la presencia de Rickettsia typhi en mamíferos o vectores en Yucatán. En la búsqueda de vectores y reservorios de Rickettsia typhi, evaluamos la presencia de bacterias del género Rickettsia en roedores y sus ectoparásitos de un pequeño municipio del estado de Yucatán por medio de técnicas de PCR convencional y secuenciación de ADN. Se identificó la presencia de Rickettsia typhi en muestras de sangre obtenidas de Rattus rattus y reportamos por primera vez la presencia de Rickettsia felis en la pulga Polygenis odiosus colectado de Ototylomys phyllotis. Complementariamente, Rickettsia felis fue detectado en la pulga Ctenocephalides felis parasitando al roedor Peromyscus yucatanicus. No se identificó especie de Rickettsia en las muestras de sangre de O. phyllotis y P. yucatanicus analizados. Nuestros resultados contribuyen también en el conocimiento de ciclo de vida biológico del género Rickettsia.

Murine Typhus: Clinical and epidemiological aspects / Tifo Murino: Aspectos clínicos y epidemiológicos

Rickettsia typhi is an intracellular bacteria who causes murine typhus. His importance is reflected in the high frequency founding specific antibodies against R. typhi in several worldwide seroepidemiological studies, the seroprevalence ranging between 3-36%. Natural reservoirs of Rickettsia typhi are rats (some species belonging the Rattus Genus) and fleas (Xenopsylla cheopis) are his vector. This infection is associated with overcrowding, pollution and poor hygiene. Typically presents fever, headache, rash on trunk and extremities, in some cases may occur organspecific complications, affecting liver, kidney, lung or brain. Initially the disease is very similar to other diseases, is very common to confuse the murine typhus with Dengue fever, therefore, ignorance of the disease is a factor related to complications or non-specific treatments for the resolution of this infection. This paper presents the most relevant information to consider about the rickettsiosis caused by Rickettsia typhi

Fibrin ring granulomas in Rickettsia typhi infection.

We describe a 71-year-old man hospitalized for fever and productive cough. Laboratory investigation showed anemia, thrombocytopenia, elevated transaminases, hyponatremia, and hypoalbuminemia. Computerized tomography of the abdomen, thorax, and sinuses, echocardiography, and a gallium scan did not reveal the source of the fever. The patient remained febrile despite courses of piperacillin-tazobactam/azithromycin and ceftriaxone/vancomycin. A bone marrow biopsy showed fibrin ring granulomas, and 2 rickettsial serologic panels were positive for Rickettsia typhi infection and negative for Q fever. The patient was given doxycycline, and the fever resolved within 48 h. We propose that fibrin ring granulomas also occur in murine typhus.

Characterization of Sec-translocon-dependent extracytoplasmic proteins of Rickettsia typhi.

As obligate intracellular, vector-borne bacteria, rickettsiae must adapt to both mammalian and arthropod host cell environments. Deciphering the molecular mechanisms of the interactions between rickettsiae and their host cells has largely been hindered by the genetic intractability of these organisms; however, research in other gram-negative pathogens has demonstrated that many bacterial determinants of attachment, entry, and pathogenesis are extracytoplasmic proteins. The annotations of several rickettsial genomes indicate the presence of homologs of the Sec translocon, the major route for bacterial protein secretion from the cytoplasm. For Rickettsia typhi, the etiologic agent of murine typhus, homologs of the Sec-translocon-associated proteins LepB, SecA, and LspA have been functionally characterized; therefore, the R. typhi Sec apparatus represents a mechanism for the secretion of rickettsial proteins, including virulence factors, into the extracytoplasmic environment. Our objective was to characterize such Sec-dependent R. typhi proteins in the context of a mammalian host cell infection. By using the web-based programs LipoP, SignalP, and Phobius, a total of 191 R. typhi proteins were predicted to contain signal peptides targeting them to the Sec translocon. Of these putative signal peptides, 102 were tested in an Escherichia coli-based alkaline phosphatase (PhoA) gene fusion system. Eighty-four of these candidates exhibited signal peptide activity in E. coli, and transcriptional analysis indicated that at least 54 of the R. typhi extracytoplasmic proteins undergo active gene expression during infections of HeLa cells. This work highlights a number of interesting proteins possibly involved in rickettsial growth and virulence in mammalian cells.

Rickettsial Seroepidemiology among farm workers, Tianjin, People's Republic of China.

High seroprevalence rates for Anaplasma phagocytophilum (8.8%), Coxiella burnetii (6.4%), Bartonella henselae (9.6%), and Rickettsia typhi (4.1%) in 365 farm workers near Tianjin, People's Republic of China, suggest that human infections with these zoonotic bacteria are frequent and largely unrecognized. Demographic features of seropositive persons suggest distinct epidemiology, ecology, and risks.