Brucella neotomae Infection in Humans, Costa Rica

Several species of Brucella are known to be zoonotic, but B. neotomae infection has been thought to be limited to wood rats. In 2008 and 2011, however, B. neotomae was isolated from cerebrospinal fluid of 2 men with neurobrucellosis. The nonzoonotic status of B. neotomae should be reassessed

The two-component system BvrR/BvrS essential for Brucella abortus virulence regulates the expression of outer membrane proteins with counterparts in members of the Rhizobiaceae

The Brucella BvrR/BvrS two-component regulatory system is homologous to the ChvI/ChvG systems of Sinorhizobium meliloti and Agrobacterium tumefaciens necessary for endosymbiosis and pathogenicity in plants. BvrR/BvrS controls cell invasion and intracellular survival. Probing the surface of bvrR and bvrS transposon mutants with monoclonal antibodies showed all described major outer membrane proteins (Omps) but Omp25, a protein known to be involved in Brucella virulence. Absence of Omp25 expression was confirmed by two-dimensional electrophoresis of envelope fractions and by gene reporter studies. The electrophoretic analysis also revealed reduction or absence in the mutants of a second set of protein spots that by matrix-assisted laser desorption ionization MS and peptide mass mapping were identified as a non-previously described Omp (Omp3b). Because bvrR and bvrS mutants are also altered in cell-surface hydrophobicity, permeability, and sensitivity to surf ace-targeted bactericidal peptides, it is proposed that BvrR/BvrS controls cell envelope changes necessary to transit between extracellular and intracellular environments. A genomic search revealed that Omp25 (Omp3a) and Omp3b belong to a family of Omps of plant and animal cell-associated alpha-Proteobacteria, which includes Rhizobium leguminosarum RopB and A. tumefaciens AopB. Previous work has shown that RopB is not expressed in bacteroids, that AopB is involved in tumorigenesis, and that dysfunction of A. tumetaciens ChvI/ChvG alters surface properties. It is thus proposed that the BvrR/BvrS and Omp3 homologues of the cell-associated a-Proteobacteria play a role in bacterial surface control and host cell interactions

Applying One Health to understand brucellosis biology

Ponencia presentada en el Congreso de la Sociedad de Microbiología del Reino Unido, el 9 de abril del 2019Members of the Brucella genus, are facultative extracellular intracellular zoonotic bacteria that cause reproductive disease in animals. The different species show strong host preference in spite of sharing 96-98% similarity at genome level. An integrated effort to understand brucellosis is taking place in Costa Rica, a tropical country of 51 000 km2 located in Central America. A total of 545 277 bovines were sampled between 2012-2016 from 8 672 herds. Sheep, goats, pigs, water buffaloes, horses and stranded cetaceans were also sampled between 1999-2016. Human and dog reported cases were documented. Seroprevalence data and the implications for the control of the disease will be presented. WGS and MLVA analysis of Brucella abortus isolated from bovines and humans indicated the presence of several clusters, some in specific areas and others widely distributed in the country. Interestingly, the human isolates constituted an unique cluster. The first two human cases worldwide of Brucella neotomae were also reported. By the same means, elements of genetic variation were described, and in Brucella from marine mammals worldwide, they are related to oceanic distribution and preferred host. Extensive pseudogenization was found in these isolates as compared to terrestrial ones. In B. ceti isolates from wildlife dolphins further degradation of specific metabolic pathways was observed. Thus, gene loss through pseudogenization is a source of genetic variation in Brucella that relates to host preference. These findings are important to understand the natural history of brucellosis, its zoonotic potential and the impact of human interventions such as vaccination and domestication.Los miembros del género Brucella son bacterias zoonóticas intracelulares extracelulares facultativas que causan enfermedades reproductivas en animales. Las diferentes especies muestran una fuerte preferencia por el huésped a pesar de compartir una similitud del 96-98% a nivel del genoma. Se está realizando un esfuerzo integrado para comprender la brucelosis en Costa Rica, un país tropical de 51 000 km2 ubicado en América Central. Un total de 545 277 bovinos fueron muestreados entre 2012-2016 de 8 672 rebaños. Ovejas, cabras, cerdos, búfalos de agua, caballos y cetáceos varados también fueron muestreados entre 1999-2016. Se documentaron casos reportados en humanos y perros. Se presentarán los datos de seroprevalencia y las implicaciones para el control de la enfermedad. El análisis de WGS y MLVA de Brucella abortus aislado de bovinos y humanos indicó la presencia de varios grupos, algunos en áreas específicas y otros ampliamente distribuidos en el país. Curiosamente, los aislados humanos constituyeron un grupo único. También se informaron los primeros dos casos en humanos de Brucella neotomae en todo el mundo. Del mismo modo, se describieron elementos de variación genética, y en Brucella de mamíferos marinos de todo el mundo, están relacionados con la distribución oceánica y el huésped preferido. Se encontró una pseudogenización extensa en estos aislamientos en comparación con los terrestres. En aislamientos de B. ceti de delfines silvestres se observó una mayor degradación de las rutas metabólicas específicas. Por lo tanto, la pérdida de genes por pseudogenización es una fuente de variación genética en Brucella que se relaciona con la preferencia del huésped. Estos hallazgos son importantes para comprender la historia natural de la brucelosis, su potencial zoonótico y el impacto de las intervenciones en humanos, como la vacunación y la domesticación.Universidad Nacional, Costa Rica Microbiology Society FEES FID

Virulence mechanisms of two gram negative bacteria : Studies on Escherichia coli hemolysin HlyA and on the interaction of Brucella abortus with non-phagocytic cells

Virulence factors may be classified in two general groups: those that cause damage to the host and those that promote bacterial colonization and invasion. In this study, the tissue damaging Escherichia coli hemolysin HlyA and the mechanism of internalization of the intracellular parasite Brucella abortus were investigated. HIyA is a pore-forming toxin belonging to the family of Gram negative exo-proteins known as RTX (from Repeat in Toxins). HIyA is activated by fatty acylation of two internal lysine residues, by a mechanism requiring acyl carrier protein and HlyC. Site directed mutagenesis studies of hlyC identified amino acid residues essential for HlyC acyl transferase activity as well as other residues that generated simultaneous secretion of bi-, mono- and non-acylated HIyA molecules. HlyC was not detected by Western blot in an E. coli strain encoding hlyC and hIyA, while four different isoforms were found in a strain encoding hlyC alone. As similar hlyC mRNA levels were found in both strains, it was concluded that HlyC was probably degraded by a HlyA dependent mechanism. Degradation of HlyC was performed by multiple protease systems such as Clp, FtsH and Lon. Internalization of B. abortus was studied by fluorescence and transmission electron microscopy. Brucella did not induce major cytoskeletal rearrangements in HeLa cells despite the fact that both, the actin and microtubule networks were needed for its uptake. Treatment of HeLa cells with different bacterial toxins specific for small GTPases together with mutant studies demonstrated that Rho, Rac and Cdc42 were involved in Brucella internalization. Moreover, immunoprecipitation of active Rho, Rac and Cdc42 demonstrated that Brucella is capable of activating Cdc42 during entry to HeLa cells. Analysis by two-dimensional gel electrophoresis of wild type and non virulent B. abortus BvrR-BvrS two component system mutants revealed differences in various protein groups in outer membrane fragments. Two protein groups were chosen for further studies. Western Blot and protein sequencing showed that one group of protein spots, absent in the mutant strains, corresponded to the outer membrane protein Omp3A (Omp25). beta-galactosidase reporter analysis indicated transcriptional regulation of omp3A under the control of BvrR-BvrS. A second family of protein spots had the same sequence and was shown to be an unknown protein, similar to membrane proteins RopA and RopB from Rhizobium melliloti. We also detected variations in the lipid A acylation level in the mutant strains as compared to the wild type strain. Intoxication of HeLa cells with cytotoxic necrotizing factor (CNF) from E. coli increased B. abortus internalization up to 10 fold as compared to non-treated cells, without altering the intracellular replication of wild type and bvrS mutant strains. Entry however was affected, since B. abortus penetrated HeLa cells by membrane ruffles induced by the toxin. It was also established that B. abortus infection does not interfere with the cytokinesis and mitosis processes of its host cell. The use of CNF will help to further elucidate the Brucella internalization process

Brucella genomics: macro and micro evolution

Se seleccionó la licencia Creative Commons para este envío. El documento trae lo siguiente: © 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). (En caso de duda consultar a Meilyn Garro).Brucella organisms are responsible for one of the most widespread bacterial zoonoses, named brucellosis. The disease affects several species of animals, including humans. One of the most intriguing aspects of the brucellae is that the various species show a ~97% similarity at the genome level. Still, the distinct Brucella species display different host preferences, zoonotic risk, and virulence. After 133 years of research, there are many aspects of the Brucella biology that remain poorly understood, such as host adaptation and virulence mechanisms. A strategy to understand these characteristics focuses on the relationship between the genomic diversity and host preference of the various Brucella species. Pseudogenization, genome reduction, single nucleotide polymorphism variation, number of tandem repeats, and mobile genetic elements are unveiled markers for host adaptation and virulence. Understanding the mechanisms of genome variability in the Brucella genus is relevant to comprehend the emergence of pathogens.Los organismos de Brucella son responsables de una de las zoonosis bacterianas más extendidas denominada brucelosis. La enfermedad afecta a varias especies de animales, incluido el ser humano. Uno de los aspectos aspectos más intrigantes de las brucelas es que las distintas especies muestran una similitud del ~97% a nivel del genoma. Aun así, las distintas especies de Brucella muestran diferentes preferencias de huésped, riesgo zoonótico y virulencia. Después de 133 años de investigación, hay muchos aspectos de la biología de Brucella que siguen siendo de la biología de Brucella, como la adaptación al huésped y los mecanismos de virulencia. Una estrategia para entender Una estrategia para comprender estas características se centra en la relación entre la diversidad genómica y la preferencia por el huésped de las distintas especies de Brucella. La pseudogenización, la reducción del genoma, el polimorfismo de un solo nucleótido de polimorfismo de un solo nucleótido, el número de repeticiones en tándem y los elementos genéticos móviles son marcadores revelados de la adaptación al huésped y la virulencia. adaptación al huésped y la virulencia. Comprender los mecanismos de variabilidad del genoma en el género Brucella es relevante para comprender la aparición de patógenos.Universidad Nacional, Costa RicaUniversidad de Costa Rica, Costa RicaEscuela de Medicina Veterinari

Estandardização de um protocolo de caraterização molecular para a identificação de espécie de cepas terrestres do gênero brucella

La brucelosis es la enfermedad zoonótica más extendida en el mundo que afecta diversos animales, incluyendo especies domésticas y de vida silvestre. Es causada por una bacteria perteneciente al género Brucella, el cual incluye nueve especies distintas e infectantes de mamíferos terrestres y marinos. Cada especie de Brucella presenta variaciones en la secuencia de ADN que afectan a los nucleótidos en una posición específica del genoma. A estas variaciones se les llama polimorfismo. El polimorfismo de las especies de Brucella localizado en los genes que codifican para las proteínas glk, omp25ytrpE, se utilizó para desarrollar un ensayo múltiple basado en la extensión de cebadores, el cual permite identificar un aislamiento como miembro de una de las nueve especies reconocidas. Los métodos tradicionales para la identificación de Brucella a nivel de especie consumen mucho tiempo y ponen en riesgo al personal laboratorial. Es por ello que la finalidad de este trabajo es evitar la ambigüedad, agilizar el procedimiento, disminuir el tiempo de respuesta y generar una herramienta laboratorial más efectiva para mejorar la vigilancia epidemiológica, el diagnóstico y el abordaje de la brucelosis en Costa Rica. El siguiente trabajo presenta la estandarización del protocolo para la extracción de ADN de Brucella, así como de una serie de amplificaciones de fragmentos de genes de interés por medio de la reacción en cadena de la polimerasa (PCR) y la estandarización de la reacción de extensión de cebadores.Brucellosis is the most widespread zoonotic disease worldwide that affects various animals, including domestic species and wildlife. It is caused by bacteria belonging to the genus Brucella, which includes nine different species and infective terrestrial and marine mammals. Each species of Brucella has variations in DNA sequence involving nucleotides in a specific position in the genome. These variations are called polymorphisms The polymorphism of Brucella species located in the genes coding for proteins glk, omp25, and trpE was used to develop a multiplex assay based on primer extension, with which it can identify an isolate as a member of nine recognized species. Traditional methods for identification of Brucella at the species level, time consuming and endanger laboratory staff. That is why the aim of this work is to avoid ambiguity, to streamline the procedure, reduce the response time and generate a more effective laboratory tool for improving epidemiological surveillance, diagnosis and approach of brucellosis in Costa Rica. This paper presents the standardization of the protocol for DNA extraction of Brucella, the standardization of a series of amplifications of fragments of genes of interest through the chain reaction (PCR) and standardization of the extension reaction primers.Brucelose é a doença zoonótica mais distribuída por todo o mundo e que afeta várias espécies animais incluindo espécies domésticas e selvagens. É causada por uma bactéria pertencente ao género Brucella que inclui nove espécies diferentes e é infectante para mamíferos terrestres e marinhos. Cada espécie de Brucella tem variações na sequência de DNA envolvendo os nucleótidos de uma posição especifica do genoma. Estas variações são chamadas polimorfismos. O polimorfismo das espécies de Brucella localizado no código genético para proteínas glk, omp25 e trpE foi utilizado para desenvolver um ensaio múltiplo baseado na primeira extensão, com a qual se pode identificar e isolar como membro de uma das 9 espécies. Os métodos tradicionais para identificação de Brucella ao nível da espécie, consomem muito tempo e põe em risco o pessoal de laboratório. É por isso que o objectivo deste trabalho é evitar a ambiguidade, agilizar o procedimento, reduzir o tempo de resposta e gerar uma ferramenta laboratorial mais efectiva para melhorar a vigilância epidemiológica, diagnostico e aproximação à brucelose na Costa Rica. Este artigo, apresenta a estandardização do protocolo para extracção de DNA de Brucella, estandardização de uma série de amplificações de fragementos genéticos de interesse através da reacção de polimerase em cadeia (PCR) e estandardização da reacção dos primers de extensão.Universidad Nacional, Costa RicaEscuela de Medicina Veterinari

In vivo proteolytic degradation of the Escherichia coli acyltransferase HlyC

Escherichia coli hemolysin (HlyA) is the prototype toxin of a major family of exoproteins produced by Gram-negative bacteria known as “repeats in toxins.” Only fatty acid-acylated HlyA molecules at residues Lys564 and Lys690 are able to damage the target cell membrane. Fatty acylation of pro-HlyA is dependent on the co-synthesized acyltransferase HlyC and the acylated form of acyl-carrier protein. By using a collection of hlyA and hlyC mutant strains, the processing of HlyC was investigated. HlyC was not detected by Western blot in an E. coli strain encoding hlyC and hlyA, but it was present in a strain encoding only hlyC. The hlyC mRNA pattern, however, was similar in both strains indicating that the turnover of HlyC does not occur at the transcriptional level. HlyC was detected in Western blots of cell lysates from an E. coli strain encoding HlyC and a HlyA derivative where both acylation sites were substituted. Similar results were obtained when HlyC was expressed in a hlyA mutant strain lacking part of a putative HlyC binding domain, indicating that this particular HlyA region affects HlyC stability. We did not detect HlyC in cell lysates from hlyC mutants with different abilities to acylate pro-HlyA, suggesting that the degradation of HlyC is not related to the HlyA acylation process. The protease systems ClpAP, ClpXP, and FtsH were found to be responsible for the HlyA-dependent processing of HlyC.La hemolisina de Escherichia coli (HlyA) es el prototipo de una importante familia de exoproteínas producidas por Bacterias Gram-negativas conocidas como "repeticiones en las toxinas". Sólo las moléculas de HlyA con ácidos grasos en los residuos Lys564 y Lys690 son capaces de dañar la célula objetivo membrana. La acilación grasa de pro-HlyA depende de la HlyC de la aciltransferasa co-sintetizada y la forma aciliada de la proteína portadora de acil. Al utilizar una colección de cepas mutantes de HlyA y HlyC, el procesamiento de HlyC fue investigado. El HlyC no fue detectado por Western blot en una cepa de E. coli que codifica hlyC y hlyA, pero fue presente en una cepa que sólo codifica el HlyC. El ARNm de hlyC Sin embargo, la pauta fue similar en ambas cepas, lo que indica que que la rotación de HlyC no se produce a nivel de transcripción. El HlyC fue detectado en manchas occidentales de lisados celulares de una cepa de E. coli que codifica HlyC y un Derivado de HlyA en el que se sustituyeron ambos sitios de acilación. Se obtuvieron resultados similares cuando HlyC fue expresada en una cepa mutante de HlyA que carece de parte de un supuesto dominio vinculante de HlyC, lo que indica que esta región particular de HlyA afecta a la estabilidad de HlyC. No detectamos HlyC en los lisados celulares de los mutantes de HlyC con diferentes habilidades para aciliar pro-HlyA, lo que sugiere que la degradación de HlyC no está relacionada con el proceso de acylación de HlyA. Los sistemas de proteasa ClpAP, ClpXP y se encontró que FtsH era responsable del procesamiento dependiente de HlyA de HlyC.Universidad Nacional, Costa RicaEscuela de Medicina Veterinari

Analysis of the association between density of Helicobacter spp and gastric lesions in dogs

OBJECTIVE To evaluate the correlation between the density of native gastric Helicobacter spp and the presence of gastric lesions in dogs. ANIMALS 80 dogs of various breeds, sexes, and ages. PROCEDURES Gastroscopic and histologic examinations were performed for all dogs. Helicobacter spp were detected by combining evaluation of urease activity and results of bacteriologic culture, microscopic observation, and a 16S rRNA PCR assay. The density of Helicobacter-like organisms was evaluated with light microscopy by use of Warthin-Starry modified stain. Correlations were evaluated by use of the Spearman correlation analysis. RESULTS Gastritis was found in 55 of 80 dogs and classified as mild (n = 31), moderate (16), or severe (8). Of these 55 dogs, only 8 had clinical signs. Histologic examination revealed some degree of lymphocytic-plasmacytic infiltrate, mild eosinophilia, and neutrophilic inflammation in the lamina propria. Seventy-six dogs had positive results for Helicobacter spp. Helicobacter pylori DNA was not detected. Low density and homogeneous distribution of Helicobacter spp were observed in all gastric zones. CONCLUSIONS AND CLINICAL RELEVANCE A significant correlation between density of Helicobacter spp and gastroscopic or histologic lesions was not detected. These findings supported the contention that there is no correlation between general Helicobacter spp density or numbers and gastritis in dogs.OBJETIVO Evaluar la correlación entre la densidad del Helicobacter gástrico nativo spp. y la presencia de lesiones gástricas en perros. ANIMALES 80 perros de varias razas, sexos y edades. PROCEDIMIENTOS Se realizaron exámenes gastroscópicos e histológicos a todos los perros. Se detectaron Helicobacter spp combinando la evaluación de la actividad de la ureasa y los resultados del cultivo bacteriológico, la observación microscópica y un ensayo PCR de ARNr 16S. La densidad de organismos similares a Helicobacter fue evaluada con microscopía de luz mediante el uso de la tinción modificada Warthin-Starry. Las correlaciones se evaluaron mediante el análisis de correlación de Spearman. RESULTADOS La gastritis se encontró en 55 de 80 perros y se clasificó como leve (n = 31), moderada (16) o severa (8). De estos 55 perros, sólo 8 tenían signos clínicos. El examen histológico reveló algún grado de infiltrado linfocítico-plasmacítico, eosinofilia leve e inflamación neutrófila en la lámina propia. Setenta y seis perros tuvieron resultados positivos para el ADN de Helicobacter spp. Helicobacter pylori no fue detectado. Se observó una baja densidad y una distribución homogénea de Helicobacter spp. en todas las zonas gástricas. CONCLUSIONES Y RELEVANCIA CLÍNICA No se detectó una correlación significativa entre la densidad de Helicobacter spp y las lesiones gastroscópicas o histológicas. Estos hallazgos apoyaron el argumento de que no hay correlación entre la densidad o el número general de Helicobacter spp y la gastritis en los perros.Universidad Nacional, Costa RicaEscuela de Medicina Veterinari

R-Ras Glucosylation and Transient RhoA Activation Determine the Cytopathic Effect Produced by Toxin B Variants from Toxin A-negative Strains of Clostridium difficile

Clostridium difficile induces antibiotic-associated di-arrhea through the production of toxin A and toxin B;the former toxin has been assumed to be responsible forthe symptoms of the disease. Several toxin A-negativestrains fromC. difficilehave recently been isolated fromclinical cases and have been reported to produce toxin Bvariants eliciting an atypical cytopathic effect. Ultra-structural analysis indicated these toxins induce arounding cytopathic effect and filopodia-like structures.Toxin B variants glucosylated R-Ras, and transfectionwith a constitutively active mutant of this GTPase pro-tected cells against their cytopathic effect. Treatment ofcells with toxin B variants induced detachment from theextracellular matrix and blockade of the epidermalgrowth factor-mediated phosphorylation of extracellu-lar-regulated protein kinases, demonstrating a deleteri-ous effect on the R-Ras-controlled avidity of integrins.Treatment with toxin B variants also induced a tran-sient activation of RhoA probably because of inactiva-tion of Rac1. Altogether, these data indicate that thecytopathic effect induced by toxin B variants is becauseof cell rounding and detachment mediated by R-Ras glu-cosylation, and the induction of filopodia-like struc-tures is mediated by RhoA activation. Implications forthe pathophysiology ofC. difficile-induced diarrhea arediscussed.El Clostridium difficile induce la diarrea asociada a los antibióticos mediante la producción de la toxina A y la toxina B; se ha asumido que la primera toxina es la responsable de los síntomas de la enfermedad. Recientemente se han aislado varias cepas de la toxina A de C. difficile en casos clínicos y se ha informado de que producen variantes de la toxina B que producen un efecto citopático atípico. Los análisis ultraestructurales indicaron que estas toxinas inducen un efecto citopático circundante y estructuras similares a las filopodias. Las variantes de la toxina B glucosilada R-Ras, y la transfección con un mutante constitutivamente activo de esta GTPasa protegieron a las células contra su efecto citopático. El tratamiento de las células con variantes de la toxina B indujo el desprendimiento de la matriz extracelular y el bloqueo de la fosforilación mediada por el factor de crecimiento epidérmico de las proteínas cinasas reguladas por el extracto de lúpulo, lo que demostró un efecto deletéreo en la avidez de integrinas controlada por la R-Ras. El tratamiento con variantes de la toxina B también indujo una activación transitoria de la RhoA, probablemente debido a la inactivación de la Rac1. En conjunto, estos datos indican que el efecto citopático inducido por las variantes de la toxina B se debe al redondeo y desprendimiento de las células mediado por la cosilación de los glúcidos de R-Ras, y la inducción de estructuras similares a filopodios está mediada por la activación de RhoA. Se discuten las implicaciones para la fisiopatología de la diarrea inducida por C. difficile.Escuela de Medicina Veterinari

Regulation of Brucella virulence by the two-component system BvrR/BvrS

The Brucella BvrR/BvrS two-component regulatory system is highly similar to the regulatory and sensory proteins of Sinorhizobium and Agrobacterium necessary for endosymbiosis and pathogenicity in plants, and very similar to a putative system present in the animal pathogen Bartonella. Mutations in the bvrR or bvrS genes hamper the penetration of B. abortus in non-phagocytic cells and impairs intracellular trafficking and virulence. In contrast to virulent Brucella, BvrR/BvrS mutants do not recruit small GTPases of the Rho subfamily required for actin polymerization and penetration to cells. Dysfunction of the BvrR/BvrS system alters the outer membrane permeability, the expression of several group 3 outer membrane proteins and the pattern of lipid A acylation. Constructs of virulent B. abortus chimeras containing heterologous LPS from the bvrS− mutant demonstrated an altered permeability to cationic peptides similar to that of the BvrR/BvrS mutants. We hypothesize that the Brucella BvrR/BvrS is a system devoted to the homeostasis of the outer membrane and, therefore in the interface for cell invasion and mounting the required structures for intracellular parasitism.l sistema regulador de dos componentes Brucella BvrR / BvrS es muy similar a las proteínas reguladoras y sensoriales de Sinorhizobium y Agrobacterium necesarias para la endosimbiosis y patogenicidad en plantas, y muy similar a un sistema putativo presente en el patógeno animal Bartonella . Las mutaciones en los genes bvrR o bvrS dificultan la penetración de B. abortus en células no fagocíticas y altera el tráfico intracelular y la virulencia. En contraste con la virulenta Brucella, Los mutantes BvrR / BvrS no reclutan pequeñas GTPasas de la subfamilia Rho requeridas para la polimerización de actina y la penetración en las células. La disfunción del sistema BvrR / BvrS altera la permeabilidad de la membrana externa, la expresión de varias proteínas de la membrana externa del grupo 3 y el patrón de acilación del lípido A. Las construcciones de virulenta B. abortus quimeras que contienen LPS heterólogos a partir de los BVRS - mutantes demostraron una permeabilidad alterada a péptidos catiónicos similares a la de los / BVRS mutantes BvrR. Nuestra hipótesis es que Brucella BvrR / BvrS es un sistema dedicado a la homeostasis de la membrana externa y, por lo tanto, en la interfaz para la invasión celular y el montaje de las estructuras necesarias para el parasitismo intracelular.Universidad Nacional, Costa RicaEscuela de Medicina Veterinari