Disbiosis bacteriana y su efecto en enfermedades bucales: una revisión bibliográfica / Bacterial dysbiosis and its effect on oral diseases: a review bibliographic

Objetivo: actualizar la información sobre la disbiosis bacteriana oral y su efecto en enfermedades bucales. Material y métodos: se realizó una revisión bibliográfica detallada, donde la búsqueda de artículos comenzó desde el 2014 con trabajos de investigación relacionados con el tema. Se aplicaron palabras clave para facilitar y delimitar el tema. En los resultados obtenidos se observa información específica de disbiosis bacteriana y los problemas y enfermedades que causan en la cavidad bucal. Conclusión: la cavidad oral es un ecosistema muy complejo e interactivo donde se desarrollan variedades de hábitats que establecen relaciones entre los microorganismos en los distintos medios bucales. Por lo general, el cuerpo humano vive en simbiosis con dichas bacterias, esta relación hospedador-huésped es producto de años de evolución y convivencia para poder tolerar a dichas especies y por medio de años de investigación, determinar a los agentes patógenos y a los simbióticos, lo que permitirá en un futuro tener enfoques terapéuticos y científicos, para así solucionar, mejorar y evitar problemas relacionados con la salud (AU)

Objective: this review aimed to update the information on oral bacterial dysbiosis and its effect on oral diseases. Material and methods: a detailed literature review was performed, where the search for articles began in 2014 with research papers related to the topic. Keywords were applied to facilitate and delimit the topic. The results obtained show specific information on bacterial dysbiosis and the problems and diseases they cause in the oral cavity. Conclusion: the oral cavity is a very complex and interactive ecosystem where a variety of habitats develop and establish relationships between microorganisms in different oral environments. Generally, the human body lives in symbiosis with these bacteria, this host-guest relationship is the product of years of evolution and coexistence to be able to tolerate these species and through years of research to determine the pathogens and symbiotics, which will allow in the future to have therapeutic and scientific approaches, to solve, improve and avoid health-related problems (AU)

Endocarditis infecciosa por bacilos gram negativos no HACEK. Experiencia en un centro de alta complejidad de la República Argentina (1998-2016) / Infective endocarditis due to non-HACEK gram-negative bacilli in a Level III cardiovascular center in Argentina (1998-2016)

Los bacilos gram negativos (BGN) que no pertenecen al grupo HACEK son una causa infrecuente de endocarditis infecciosa. Los aspectos epidemiológicos, diagnósticos y pronósticos de esta entidad son poco conocidos y la experiencia aún es limitada. Nuestros objetivos fueron analizar las características clínicas y microbiológicas de las endocarditis infecciosas (EI) por BGN no HACEK diagnosticadas en un centro de alta complejidad de Argentina en el período 1998-2016 y conocer su evolución hospitalaria, a fin de compararlas con las EI debidas a otros microorganismos.

Non-HACEK Gram-negative bacilli are a rare cause of infective endocarditis. Epidemiological, diagnostic and prognostic aspects of this entity are little known, and there is limited experience. The aim of this study was to analyze the clinical, microbiological and in-hospital outcomes of non-HACEK Gram negative bacilli endocarditis and to compare them with those due to other microorganisms.

¿Cuál es el nivel de contaminación del cepillo de dientes almacenado en diferentes entornos sanitarios? / What is the level of toothbrush contamination stored in different sanitary settings?

Introducción: Los cepillos pueden albergar una amplia variedad de microorganismos, incluyendo bacterias hongos y virus, pudiendo así facilitar la translocación de especies en un mismo individuo y la transmisión de especies entre individuos. Métodos: Estudio de la contaminación bacteriana de los cepillos de dientes de cien voluntarios con la cumplimentación de un cuestionario (lugar de almacenamiento, tipo de cepillo, utilización de estuche de almacenamiento y meses de uso). Resultados: Se estudiaron un total de 100 muestras. El 33% guardaba el cepillo fuera del baño, un 20% lo guardaba en el cajón del baño y un 47% sobre el lavabo del baño. El 92% de las muestras estaban contaminadas como mínimo con un grupo de microorganismos Conclusión: El lugar de almacenamiento del cepillo de dientes es fundamental en la reducción de la contaminación. Se debe guardar en un lugar seco, lejos del inodoro y sin estuche

Introduction: Brushes can house a wide variety of microorganisms, including fungal bacteria and viruses, which can facilitate the translocation of species in the same individual and the transmission of species between individuals. Methods: Study of the bacterial contamination of toothbrushes of one hundred volunteers with the completion of a questionnaire (place of storage, type of brush, use of storage case and months of use). Results: A total of 100 samples were studied. 33% kept the brush outside the bathroom, 20% kept it in the bathroom drawer and 47% on the bathroom sink. 92% of the samples were contaminated with at least one group of microorganisms. Conclusion: The storage place of the toothbrush is fundamental in the reduction of contamination. It should be stored in a dry place, away from the toilet and without a box

Resistencia antimicrobiana en bacilos gramnegativos: una amenaza actual y global / Antimicrobial resistance in Gram-negative bacilli: a current and global threat

La resistencia a los antimicrobianos se ha incrementado de manera preocupante en los bacilos gramnegativos. La dispersión de clones de alto riesgo multirresistentes con determinantes genéticos responsables de la producción de betalactamasas de espectro extendido y, más recientemente, de carbapenemas ha reducido notablemente las alternativas terapéuticas. En España es preocupante la dispersión de las enterobacterias productoras de carbapenemasas de tipo OXA-48 y KPC. Se ha notificado el hallazgo de aislados de Klebsiella pneumoniae con KPC de clones similares a los descritos en Italia, con resistencia a la colistina por mutaciones en los sistemas que afectan a la estructura del lipopolisacárido. En Pseudomonas aeruginosa y Acinetobacter baumannii, las tasas de aislados multirresistentes son similares a las de los países de nuestro entorno y se han detectado clones de alto riesgo con carbapenemasas. Recientemente se ha descrito el gen mcr-1 en Escherichia coli y K. pneumoniae asociado a plásmidos que presentan genes de betalactamasas de espectro extendido y de carbapenemasas. También preocupa el posible incremento de la resistencia a la fosfomicina en E. coli, que se está produciendo asociado a genes tipo fosA ligados a plásmidos y que podrían limitar el uso futuro de este antimicrobiano. El llamamiento de la Organización de las Naciones Unidas a la lucha unificada de los distintos estados miembros frente a la resistencia debe impulsar el desarrollo de nuevos antimicrobianos y la puesta en marcha a nivel local de los planes de contención de la resistencia (AU)

Antimicrobial resistance has dramatically increased in gram-negative bacilli. The dispersion of multiresistant high-risk clones with genetic determinants responsible for the production of extended spectrum beta-lactamases (ESBL) and, more recently, carbapenemases has markedly reduced current therapeutic alternatives. In Spain, the dispersion of OXA-48 and KPC carbapenemase-producing enterobacteria (EPC) is worrisome. KPC producing Klebsiella pneumoniae clones with resistance to colistin similar to those described in Italy has been reported in our country. Resistance mechanisms include mutations affecting the lipopolysaccharide structure. In Pseudomonas aeruginosa and Acinetobacter baumannii the rates of multiresistant isolates are similar to those in surrounding countries and high-risk clones with carbapenemases within these organisms have been detected. Recently, the mcr-1 gene has been described in Escherichia coli and K. pneumoniae associated with plasmids presenting ESBL and carbapenemase genes. Moreover, there is also concern about the potential increase of fosfomycin resistance in E. coli. This resistance has been associated with plasmid-mediated fosA-like gene and might limit future use of this antimicrobial. The high-level meeting of the United Nations celebrated with the aim that all member states fight against antimicrobial resistance must include promotion of the development of new antimicrobials and the implementation of resistance containment plans at the local level (AU)

Rol de las formas cocoides de Helicobacter pylori en la infección y la recrudescencia / Role of Helicobacter pylori coccoid forms in infection and recrudescenc

Helicobacter pylori es un bacilo espiral gramnegativo que coloniza el estómago humano y desempeña un papel clave en la patogénesis de diferentes enfermedades gastroduodenales. Sin embargo, cuando se expone a condiciones de estrés ambientales, tales como el aumento de la tensión de oxígeno, la incubación prolongada o la exposición a antibióticos, Helicobacter pylori entra en un estado viable pero no cultivable, en el cual la bacteria modifica su morfología de una forma bacilar a una cocoide como manifestación de adaptación celular a estas condiciones adversas. En el tejido gástrico, las formas cocoides viables pueden permanecer latentes durante mucho tiempo y retener factores de virulencia, por lo que estas formas posiblemente puedan contribuir a los fracasos del tratamiento y la recurrencia de la infección y de las enfermedades gastroduodenales también. En esta revisión se discutirán varios aspectos de la adaptación celular y supervivencia de Helicobacter pylori, la susceptibilidad a los antibióticos y la virulencia de las formas cocoides y su participación en la recrudescencia

Helicobacter pylori is a spiral Gram-negative bacillus, which colonizes the human stomach and plays a key role in the pathogenesis of a number of gastroduodenal diseases. However, when expose to environmental stressed conditions, such as increased oxygen tension, extended incubation and exposure to antibiotics, Helicobacter pylori is able to entering the viable but nonculturable state, in which the bacterium modifies its morphology from a spiral to coccoid form, as a manifestation of cell adaptation to these adverse conditions. In gastric tissues, viable coccoid forms may remain latent for long time and retain virulence factors, so these forms possibly contribute to the treatment failures and recurrence of Helicobacter pylori infection and gastroduodenal diseases as well. In this review, we will discuss several aspects of cellular adaptation and survival of Helicobacter pylori, antibiotic susceptibility and virulence of coccoid forms and its involvement with recrudescence

¿Es la cuantificación del biofilm un elemento diferenciador en la patogenia de bacilos gramnegativos? / Biofilm score: is it a differential element within gram negative bacilli?

El objetivo del estudio fue investigar la formación de biofilms en bacterias gramnegativas y cuantificar la producción de biofilm mediante la aplicación de una técnica que permitiese una comparación de los resultados de la formación de biofilm entre las diferentes especies de gramnegativos. Se estudiaron un total de 153 cepas de bacilos gramnegativos correspondientes a 12 especies bacterianas por el método de la densidad óptica aplicando una modificación de la técnica descrita por Stepanovic et al. Los valores obtenidos mediante el análisis de la densidad óptica permiten clasificar a los microorganismos en formadores fuertes, moderados, débiles y no formadores. Los resultados obtenidos se han expresado de dos maneras, ambas utilizando el mismo método estadístico: sin estandarizar, donde los controles fueron diferentes dependiendo de los días en los que se realizaron las medidas; y estandarizados mediante un factor de corrección, utilizando el mismo control para todas las cepas de cada especie, lo que permite su homogeneización. Los resultados obtenidos en el estudio tras el análisis y estandarización establecen que de las 153 cepas de gramnegativos estudiados, 105 de ellas fueron no formadoras de biofilms, representando el 63,75% de los géneros estudiados. Consideramos que la estandarización y cuantificación de la producción de biofilm entre las bacterias gramnegativas puede resultar de utilidad en el ámbito clínico, ya que el conocimiento de la capacidad de producción de biofilm puede dirigir o enfocar el tratamiento de elección de las patologías producidas por dichos microorganismos(AU)

The aim of the study was to investigate biofilm formation in Gram negative bacteria and to quantify biofilm production applying a new developed technique that made possible to compare results about biofilm formation within the different Gram negative bacteria species. A total of 153 Gram negative strains corresponding to 12 different bacterium species were studied applying a variation of the optic density measurement technique reported by Stepanovic et al. Data obtained with optic density analysis allow to classify microorganisms in strong biofilm developers, moderate biofilm developers, weak biofilm developers and no biofilm developers. The results were expressed in two ways, using in both cases the same statistical method: without standardization, where controls were different depending on the day optic density measurements were performed, and standardized using a correction factor, using the same control for every strain of all our bacterium species in our study, which allows result homogenization. The obtained results in our study after data analysis and standardization show that over the 153 Gram negative strains in our study, 105 of them were no biofilm developers, representing 63.75% of all the studied bacterium genera. We consider that standardization and quantification of biofilm development in Gram negative bacteria can be useful in clinical practice, because biofilm development ability can lead or focus the gold treatment of pathologies produced by these microorganisms(AU)

Una alternativa para mejorar el diagnóstico de la tuberculosis con baciloscopia negativa y otros problemas broncopulmonares en Cuba / An alternative for improving the diagnosis of smear-negative tuberculosis and other bronchopulmonary disorders in Cuba

OBJETIVO: El diagnóstico de los pacientes con tuberculosispulmonar y muestras negativas para bacilos ácido-alcoholresistentes (BAAR) representa un desafío clínico y de saludpública, por lo que en Ciudad de La Habana se creó en 1995una comisión para esclarecer su diagnóstico. El objetivo deeste estudio ha sido describir los progresos y resultados deltrabajo de esta comisión entre 1996 y 2003.PACIENTES Y MÉTODOS: Se han analizado los datos recogidosde cada paciente presentado en las sesiones de la comisión:procedencia, diagnóstico de sospecha planteado por el médicoque presentó el caso, antecedentes de tratamiento anteriorcon antibióticos y diagnóstico realizado por la comisión.RESULTADOS: Del total de 1.703 pacientes presentados aesta comisión para esclarecer el diagnóstico, un 84,8%procedía de la Ciudad de La Habana, el 48,4% pertenecía algrupo de edad igual o mayor de 55 años y el 63,8% eranvarones. El porcentaje de casos consultados con tratamientoespecífico contra la tuberculosis ya comenzado fue en 2001-2003 del 11,3%, y en el período 1996-2000, del 16,9% (p =0,001). En 1986-2000, de 918 pacientes que completaron susexámenes, tuvo diagnóstico final de tuberculosis activa un43,1%, y en 2001-2003, el 52,2% de 619 (p = 0,000). De untotal de 344 casos estudiados con sospecha de tuberculosispulmonar con BAAR y cultivo negativos en 2001-2003, eldiagnóstico se corroboró en 128 (37,2%).CONCLUSIONES: Los resultados indican que el trabajo dela comisión es viable, sostenible y de utilidad porque evita elsobrediagnóstico y el tratamiento inapropiado, además decumplir una función docente

OBJECTIVE: The diagnosis of tuberculosis in patients withnegative acid-fast bacillus smears poses a challenge to bothclinicians and public health authorities. In an attempt to aiddiagnosis in such cases, an expert committee was establishedin Ciudad de La Habana, Cuba in 1995. The aim of this studywas to describe the progress of the committee’s work and thecorresponding results for the period 1996 through 2003.PATIENTS AND METHODS: For each patient studied by thecommission, we analyzed the following data: patient’sresidence and referring center, tentative diagnosis proposedby the attending physician, history of antibiotic treatment,and final diagnosis made by the commission.RESULTS: Of the 1703 patients studied, 84.8% were from LaHabana, 48.4% were 55 years or older, and 63.8% were men.Between 2001 and 2003, 11.3% of patients were already onantituberculosis treatment when their case was studied by thecommission. The corresponding percentage for 1996 through2000 was 16.9% (P=.001). Active tuberculosis was confirmedin 43.1% of a total of 918 patients with full test results duringthe period 1996 through 2000 and in 52.2% of a total of619 patients (52.2%) during the period 2001 through 2003(P<.001). Of 344 patients with suspected pulmonary tuberculosisand negative acid-fast bacillus smears between 2001 and 2003,128 (37.2%) were diagnosed with active tuberculosis.CONCLUSIONS: These findings indicate that the work of thecommission is viable, sustainable, and useful for preventingoverdiagnosis and inappropriate treatment, and that it also serves an educational purpose

Pink-pigmented non-fermentative gram-negative rods associated with human infections: a clinical and diagnostic challenge.

Over the past several decades, the appearance of pink-pigmented bacteria in clinical specimens has gone from being a microbiologic curiosity in the clinical laboratory to the recognition of these aerobic microorganisms as etiologic agents of human disease, most notably bloodstream infections. Advances in the fields of molecular taxonomy and phylogenetics indicate that at least four distinct genera and eight different species are associated with clinical infections in susceptible patient populations. However, these bacteria are slow growing and present multiple diagnostic challenges to the microbiology laboratory including culture, isolation, and identification to species rank. This article provides a current review of these unusual non-fermentative chromogenic bacteria including their disease spectrum, taxonomy, and laboratory identification. The review also highlights the pitfalls or shortcomings we currently have in our knowledge of these microbes and their disease-producing capabilities.

Incidencia de infecciones nosocomiales en la unidad de cuidados intensivos pediátrico Hospital Militar Dr. Carlos Arvelo: 2004-2005 / Incidence of infectious nosocomial in the unit of cares intensive pediatric Hospital Militar Dr. Carlos Arvelo: 2004-2005

Las infecciones nosocomiales representan un problema de morbilidad y mortalidad en las Unidades de Cuidados Intensivos Pediátricos. Este trabajo se realiza para conocer la prevalencia de gérmenes patógenos en la Unidad de Cuidados Intensivos Pediátricos del Hospital Militar "Dr. Carlos Arvelo". Se realiza un estudio retrospectivo entre enero de 2003 y enero de 2004 de 122 pacientes que ingresaron durante ese período, se tomaron cultivos de: sangre, secreción endotraqueal, orina, punta de catéteres, etc. Del total de pacientes, 57 presentaron cultivos positivos: hemocultivo 40,3 por ciento, secreción endotraqueal 29,8 por ciento, punta de catéter 15,7 por ciento, urocultivo 8,7 por ciento. Los gérmenes mayormente aislados fueron: bacilos gram negativos no fermentador en 26,3 por ciento, estafilococo coagulasa negativo 33,3 por ciento, Levaduras 15,7 por ciento, Pseudomona aeuruginosa 12,2 por ciento, cándida albicans 10,5 por ciento, enterobacterias 3,5 por ciento. Es importante resaltar que en nuestros casos hubo la presencia de bacterias productoras de batalactamasa como Escherichia coli en un 26 por ciento y Klebsiella pneumoniae en 7 por ciento. Al conocer la epidemiolog¡a de la Unidad obtenemos conocimientos acerca de sensibilidad, mecanismos de resistencia para definir el mejor control sobre estas infecciones y así lograr mejorar la morbilidad y mortalidad y disminuir la estadia de los pacientes.

Potentially multidrug-resistant non-fermentative Gram-negative pathogens causing nosocomial pneumonia.

Owing to its high morbidity and mortality, nosocomial pneumonia represents a particularly serious illness and one of the most frequent complications in ventilated patients admitted to the Intensive Care Unit. Gram-negative microorganisms, such as Pseudomonas aeruginosa, Acinetobacter baumannii and Stenotrophomonas maltophilia, are the most relevant pathogens responsible for particularly difficult-to-treat nosocomial pneumonia. The intrinsic resistance of these bacteria to many antimicrobial agents and, in addition, the variety of their increasingly recognised acquired resistance mechanisms make their management in the hospital setting problematic. Antimicrobials that retain the best activity against P. aeruginosa include carbapenems, piperacillin, cefepime, ceftazidime, ciprofloxacin and certain aminoglycosides, whilst carbapenems and sulphamethoxazole/trimethoprim remain the most active agents against A. baumannii and S. maltophilia, respectively. However, the growing emergence among these microorganisms of multidrug-resistant (MDR) isolates and the severity of associated infections call for potential alternative drugs. Sulbactam alone or in combination with ampicillin may represent an acceptable option for MDR A. baumannii as well as colistin, which also covers MDR P. aeruginosa. Newer fluoroquinolones and some tetracyclines may be alternative drugs both for MDR S. maltophilia and A. baumannii. However, large-scale controlled clinical trials are needed to confirm these promising therapeutic options.

Spatial stochastic simulation offers potential as a quantitative method for pest risk analysis.

Pest risk analysis represents an emerging field of risk analysis that evaluates the potential risks of the introduction and establishment of plant pests into a new geographic location and then assesses the management options to reduce those potential risks. Development of new and adapted methodology is required to answer questions concerning pest risk analysis of exotic plant pests. This research describes a new method for predicting the potential establishment and spread of a plant pest into new areas using a case study, Ralstonia solanacearum, a bacterial disease of potato. This method combines current quantitative methodologies, stochastic simulation, and geographic information systems with knowledge of pest biology and environmental data to derive new information about pest establishment potential in a geographical region where a pest had not been introduced. This proposed method extends an existing methodology for matching pest characteristics with environmental conditions by modeling and simulating dissemination behavior of a pest organism. Issues related to integrating spatial variables into risk analysis models are further discussed in this article.

Characterization of a Ralstonia solanacearum operon required for polygalacturonate degradation and uptake of galacturonic acid.

The bacterial wilt pathogen Ralstonia solanacearum produces three extracellular polygalacturonases (PGs): PehA, PehB, and PehC. All three PGs hydrolyze pectin's polygalacturonic acid backbone, but each releases different reaction products. PehA and PehB contribute significantly to pathogen virulence, probably by facilitating root invasion and colonization. To determine the collective contribution of PGs to virulence and saprophytic survival, we cloned, characterized, and mutated the R. solanacearum pehC gene, which encodes a distinctive monogalacturonate-releasing exo-PG. The virulence of a pehC mutant on tomato was indistinguishable from that of its wild-type parent; thus, this exo-PG alone does not contribute significantly to wilt pathogenesis. Unexpectedly, a completely PG-deficient triple pehA/B/C mutant was slightly more virulent than a pehA/B mutant. PehC may degrade galacturonide elicitors of host defense, thereby protecting the pathogen from plant antimicrobial responses. A galacturonate transporter gene, exuT, is immediately downstream of pehC and the two genes are co-transcribed. It has been hypothesized that galacturonic acid released by PGs from plant cell walls nourishes bacteria during pathogenesis. To separate the pectolytic and nutrient-generating roles of the PGs, we made an exuT mutant, which still produces all three isozymes of PG but cannot uptake PG degradation products. This exuT mutant had wild-type virulence on tomato, demonstrating that metabolism of galacturonic acid does not contribute significantly to bacterial success inside the plant.

Ectopic expression of Ralstonia solanacearum effector protein PopA early in invasion results in loss of virulence.

Ralstonia solanacearum OE1-1 (OE1-1) is pathogenic to tobacco. The type III-secreted effector protein popA of OE1-1 showed 97.6% identity to popA of R. solanacearum GMI1000, which is not pathogenic to tobacco. Reverse transcription-polymerase chain reaction analysis showed that popA in OE1-1 was expressed at 3 h after inoculation (HAI), but not before, in infiltrated-tobacco leaves. Pathogenicity analysis using a popABC operon-deleted mutant of OE1-1 (deltaABC) showed that popABC is not directly involved in the pathogenicity of OE1-1. When Papa, which constitutively expresses popA, was infiltrated into tobacco leaves, popA was expressed by 0.5 HAI. Papa could no longer multiply or spread in tobacco leaves and was no longer virulent. Moreover, the hypersensitive response (HR) and expression of HR-related genes were not induced in Papa-infiltrated leaves. Papa was also avirulent in a tobacco root-dipping inoculation assay. These results suggest that the expression of popA in Papa immediately after invasion triggers the suppression of bacterial proliferation and movement, resulting in loss of virulence. However, Papa retained its virulence when directly inoculated into xylem vessels. This result suggests that tobacco plants can recognize PopA when it is expressed early in disease development, and respond with an effective defense in the intercellular spaces.

Bacterial diversity in soil in response to different plants, phosphate fertilizers and liming

The diversity of bacterial isolates from soil in response to different plants (control, Brachiaria ruziziensis and Cajanus cajan), fertilization (control, simple superphosphate and rock phosphate) and liming (with and without lime) was evaluated. Phenotypic and physiological characteristics of the isolates were recorded and organized in a file to identify the bacteria. Among the isolates, 95 percent were Gram-positive and 5 percent Gram-negative rods. Soil cultivated with B. ruziziensis favored the nonsporing Gram-positive and Gram-negative rods compared to soil with C. cajan or uncultivated. Number of spore-forming Gram-positive rods were higher in plots with superphosphate than in unfertilized soil or soil fertilized with rock phosphate. In unfertilized plots, larger number of Gram-positive cocci and Gram-negative rods was obtained than in fertilized plots. Unlimed plots favored spore-forming Gram-positive rods, Gram-positive cocci and Gram-negative rods, while liming a larger proportion of nonsporing Gram-positive rods was found. From 7 to 86 percent of the total isolates utilized different carbohydrates. The recording data used in this experiment was effective in the isolates identification, and might be useful for diagnosis of soil bacteria. Bacillus, Cellulomonas, Rhodococcus, Enterobacter, Flavobacterium, Micrococcus and Arthrobacter were the genera more commonly found. Bacterial diversity was enhanced in limed, unfertilized and plant cultivated plots.

PopP1, a new member of the YopJ/AvrRxv family of type III effector proteins, acts as a host-specificity factor and modulates aggressiveness of Ralstonia solanacearum.

A functional analysis of an 11-kb-long region of the genome of the plant-pathogenic bacterium Ralstonia solanacearum, previously identified as an alternative codon usage region (ACUR), reveals that it was probably acquired through horizontal gene transfer. This ACUR encodes an insertion sequence and eight potential proteins, one of which is partially homologous with a host-specificity factor from a plant-pathogenic Erwinia sp., and another, PopP1, which is homologous to members of the YopJ/AvrRxv family of type III-secreted bacterial effectors controlling interaction between bacteria and their hosts. The analysis of mutants affecting all except one of the genes identified in the ACUR showed that only the popP1-deficient strain had an altered phenotype in plant infection tests. This mutant strain became pathogenic to a Petunia line that is resistant to the wild-type strain. Therefore, popP1 behaves as a typical avirulence gene. We demonstrate that PopP1 protein is secreted and that secretion of this protein requires a functional type III-secretion pathway. In contrast to the structural genes for other type III-secreted proteins identified in R. solanacearum, transcription of the popP1 gene is not coregulated with transcription of hrp genes but is constitutive.

A R2R3-MYB gene, AtMYB30, acts as a positive regulator of the hypersensitive cell death program in plants in response to pathogen attack.

Hypersensitive response (HR) is a programmed cell death that is commonly associated with disease resistance in plants. Among the different HR-related early induced genes, the AtMYB30 gene is specifically, rapidly, and transiently expressed during incompatible interactions between Arabidopsis and bacterial pathogens. Its expression was also shown to be deregulated in Arabidopsis mutants affected in the control of cell death initiation. Here, we demonstrate that overexpression in Arabidopsis and tobacco of AtMYB30 (i) accelerates and intensifies the appearance of the HR in response to different avirulent bacterial pathogens, (ii) causes HR-like responses to virulent strains, and (iii) increases resistance against different bacterial pathogens, and a virulent biotrophic fungal pathogen, Cercospora nicotianae. In antisense AtMYB30 Arabidopsis lines, HR cell death is strongly decreased or suppressed in response to avirulent bacterial strains, resistance against different bacterial pathogens decreased, and the expression of HR- and defense-related genes was altered. Taken together, these results strongly suggest that AtMYB30 is a positive regulator of hypersensitive cell death.

Development, characterization, and preliminary evaluation of a temperature-sensitive mutant of Ornithobacterium rhinotracheale for potential use as a live vaccine in turkeys.

A temperature-sensitive (Ts) mutant strain of Ornithobacterium rhinotracheale (ORT) was developed after exposure of the wild-type organism to N-methyl-N'-nitro-N-nitrosoguanidine. The Ts mutant strain grew at 31 C but had its growth inhibited at 41 C unlike wild-type parent strain. The Ts mutant and parent strains were characterized. Morphologic and biochemical properties of wild-type and mutant strains did not show any differences. The strains were also characterized by polymerase chain reaction (PCR)-based fingerprinting methods. Results showed similar patterns in repetitive sequences by repetitive PCR (enterobacterial repetitive intergenic consensus, highly conserved repeated DNA elements present in Streptococcus pneumoniae (BOX), repetitive extragenic palindromic, and Salmonella enteritidis repetitive element primers); however, random amplified polymorphic DNA fingerprinting was able to differentiate mutant and parent strains showing a unique pattern for each of the ORT strains. The rationale for the use of a Ts strain as a vaccine is based on the ability of the mutant to colonize the upper respiratory tract but not the lower respiratory tract and systemic system of the birds, where the wild-type strain causes severe lesions. In a preliminary evaluation, Ts strain of ORT was recovered from tracheas and choanae of Ts-treated turkeys for 13 days postadministration of the strain either in drinking water or by oculonasal instillation. Humoral immune response was detected in Ts-vaccinated but not in control group birds after 3 wk postadministration. Results suggest that Ts strain of ORT has promising potential use as a live vaccine for ORT.

Minimization of pathologic changes in Ornithobacterium rhinotracheale infection in turkeys by temperature-sensitive mutant strain.

The protection elicited by a temperature-sensitive (Ts) mutant of Ornithobacterium rhinotracheale (ORT) vaccine against challenge with pathogenic strain was investigated. In Experiment 1, specific serologic response to ORT was detected in 12%-19% of Ts-vaccinated birds at 3 wk postvaccination by either drinking water or oculo-nasal instillation. At 7 days postchallenge, 100% of Ts-vaccinated turkeys of all groups were able to respond with an ORT-specific antibody response, but the control group was not, suggesting the potential of Ts strain to evoke immune protection. The study also revealed a statistically significant ability of the Ts strain to protect vaccinated turkeys against gross lesions caused by the pathogenic strain of ORT in treated groups vs. control. In Experiment 2, seroconversion was detected by enzyme-linked immunosorbent assay in birds after they were given the Ts strain in drinking water in field conditions. The results of the field study showed mean scores of gross lesions of nonvaccinated/challenged groups to be up to seven times higher than those of the vaccinated/challenged group. In addition, reisolation rates and quantification of ORT colonies per gram of lung tissue were significantly lower for vaccinated/challenged than for nonvaccinated/challenged turkeys. In conclusion, results from laboratory and field experiments suggest that use of the Ts mutant strain of ORT as a live vaccine would be a suitable method to evoke protection against ORT infection in turkeys.