1,721,076 research outputs found
Isolation and characterisation of novel bacteriophages for clostridium difficile
No full textClostridium difficile é um patogénico muito importante e a maior causa de diarreia infeciosa na Europa e na América do Norte. O ribótipo mais comum em humanos é o 027 e nos animais, nomeadamente em porcos, é o 078. A infeção por C. difficile tem vindo a aumentar por todo o mundo, assim como o número de isolados resistentes a antibióticos. Em algumas pessoas, C. difficile pertence à microbiota normal do intestino. Contudo, pode tornar-se oportunista quando a comunidade microbiana é suprimida pela toma de antibióticos como clindamicina, cefalosporinas, penincilina e fluoroquinolonas. Para além disso, os esporos produzidos por estas bactérias conseguem resistir à terapia por antibióticos e germinar. Isto suporta a necessidade de criar terapias alternativas. Bacteriófagos (fagos) são vírus que infetam bactérias. A terapia fágica é uma potencial alternativa à convencional antibioterapia. Esta terapia é mais específica do que outros tratamentos usados atualmente, uma vez que os fagos só afetam a bactéria alvo. Isto reduz as probabilidades de efeitos laterais. A manipulação do genoma destes vírus é outra vantagem para o uso desta terapia. Além do mais, a investigação de fagos é mais rápida e barata do que outras terapias recomendadas para a infeção por C. difficile. Este estudo teve como objetivo o isolamento de bacteriófagos que infetem estirpes de C. difficile dos ribótipos mais comumente isolados nomeadamente, 023, 027 e 078. Três fagos ΦCD24-01, ΦCD78-01 e ΦCDL11 foram isolados e propagados em amostras ambientais recolhidas em três países Europeus, Polónia, Portugal e Reino Unido. O fago ΦCD24-01 foi isolado usando C. difficile ribótipo 023 e a caracterização taxonómica mostrou que pertence à família Siphoviridae. Os outros dois fagos ΦCD78-01 e ΦCDL11 foram isolados usando células hospedeiras dos ribótipos 023 e 027, respetivamente. A avaliação do desempenho lítico do fago anteriormente reportado, ΦCD1801, confirmou a ampla infeção das estirpes de 078, suportando o uso deste para controlo de C. difficile do ribótipo 078. Os fagos reportados neste estudo podem ser boas alternativas quando usados em cocktail fágico com alvo nos principais ribótipos de C. difficile que afeta porcos e humanos.Clostridium difficile is a very important nosocomial pathogen and it is the most common cause of infectious diarrhea in Europe and North America. The most common PCR ribotype found in humans is the 027 and in animals, namely in pigs, the 078. Clostridium difficile infection (CDI) has been increasing worldwide as well as the number of antibiotic resistant isolates. In some people C. difficile belongs to the normal gut microbiota, although becomes opportunist when the microbial community is suppressed by taking some antibiotics such as clindamycin, cephalosporins, penicillin, and fluoroquinolones. Furthermore, the spores produced by these bacteria can resist antibiotic therapy and germinate. This supports the need of coming up with alternative therapies. Bacteriophages (phages) are viruses which infect bacteria and phage therapy is a potential alternative to conventional antibiotherapy. They are more specific than the other treatments currently used since they only affect the target bacteria. This reduces the probability of side effects. The genome manipulation of these viruses is another advantage for the use of this type of therapy. In addition, the phage research is more rapid and cheaper than the other therapies recommend for CDI. This study aimed at isolating bacteriophages targeting C. difficile strains from the most commonly isolated PCR ribotypes namely 023, 027 and 078. Three phages, ΦCD24-01, ΦCD78-01 and ΦCDL11 were isolated and propagated from environmental samples collected in three European countries, Poland, Portugal and The United Kingdom. The phage ΦCD24-01 was isolated using a C. difficile ribotype 023 and its taxonomic characterisation showed that it belongs to the Siphoviridae family. The other two phages ΦCD78-01 and ΦCDL11 were isolated using a 023 and a 027 host cell, respectively. The lytic performance evaluation of a previously reported phage, ΦCD1801, confirmed its wide infection of 078 strains supporting its use for the control of important C. difficile ribotype 078 isolates. Phages reported in this study may be good alternatives when employed as a phage cocktail targeting the main C. difficile PCR ribotype affecting pigs and humans
Influence of acetate concentration on acetone production by a modified Acetobacterium woodii
Full text linkGlobal warming is the driving force for developing production processes of chemical compounds based on CO2 reduction technologies. Bacteria can act as biological catalysts that reduce this gaseous substrate in added-value compounds. Acetobacterium woodii is one of the best-performing strains on H2–CO2 blends and naturally produces acetate. Acetone is a raw material deeply used in the chemical industry, and its global demand is increasing. Acetone-butanol-ethanol (ABE) fermentation is the oldest microbial production platform for acetone synthesis from organic substrates, and Clostridium acetobutylicum is the model strain for its production. In various wild-type acetogens and ABE-producing Clostridium species, acetate positively influences the synthesis of reduced products. In this work, a modified A. woodii strain expressing the enzymes of the acetone pathway from C. acetobutylicum was used to convert H2–CO2 streams into acetone. This study aims to assess the impact of acetate on acetone production catalyzed by such a modified A.woodii. Tests were carried out in serum bottles and a continuous stirred tank reactor up to a pressure of 10 bar, in as-batch or in continuous gassing, providing different gas mixes. Outcomes indicated that acetone synthesis was stimulated when acetate concentration in the medium exceeded the threshold of 100–120 mM. Thus, acetic acid can affect acetone productivity in the modified A. woodii strain. This outcome should be considered in the design of fermentation processes, especially in setting up fermentations with the liquid continuous operative mode
Complete Genome Sequence of the Nonpathogenic Soil-Dwelling Bacterium Clostridium sporogenes Strain NCIMB 10696
No full textClostridium sporogenes is a harmless spore-forming anaerobe that is widely distributed in soil/water and in the intestines of humans and animals. It is extensively used as a safe model to test the suitability of new preservative methods by the food industry and has potential to deliver therapeutic agents to tumors
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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