1,720,955 research outputs found
Class 3 integrons : machanistical and epidemiological aspects
No full textLes intégrons sont des supports génétiques bactériens de capture, d’expression et de dissémination de gènes de résistance aux antibiotiques sous forme de cassettes. Ils sont majoritairement décrits chez les bactéries à Gram négatif chez qui ils confèrent généralement un phénotype de multirésistance. Les intégrons de résistance (IR) jouent un rôle majeur dans l’acquisition de la résistance dans le monde bactérien. Il existe 3 principales classes d’IR ; les IR de classe 1, les IR de classe 2 et les IR de classe 3 (IR3). Contrairement aux 2 premières classes, les IR3 représentent la classe d’intégrons de résistance la moins étudiée. Très peu de travaux s’intéressent à leur étude et on dénombre actuellement moins de 10 IR3 entièrement caractérisés. Les objectifs de ce travail de thèse étaient (i) d’effectuer une étude épidémiologique des IR3 en France et au Cameroun et (ii) d’étudier les modalités d’expression de l’intégrase et des cassettes de ces intégrons. Nos travaux ont permis d’isoler puis de décrire 3 nouveaux IR3 présents au sein de bactéries environnementales appartenant aux genres Aeromonas, Acinetobacter et Citrobacter. Les cassettes de ces IR3 codent des résistances aux bétalactamines, aminosides et ammoniums quaternaires. De plus, nous avons caractérisé des IR3 dans 3 souches de Delftia spp. (2 D.acidovorans et 1 D. tsuruhatensis) isolées en Afrique ; les cassettes de ces intégrons ne codent pas de résistance aux antibiotiques. L’axe plus fondamental de ce travail de thèse a permis de montrer que le PintI3(1) est le promoteur impliqué dans l’expression du gène intI3. De plus, nous avons montré que les variants du promoteur Pc, ainsi que les variants du promoteur PintI3(1) sont fonctionnels et de force différente. Il ressort de nos travaux que l’environnement constituerait un réservoir d’intégrons de classe 3 et que ces supports génétiques pourraient jouer un rôle important dans la dissémination de la résistance au sein de cet écosystème.Integrons are bacterial genetic elements able to capture and express genes embedded within gene cassettes. They are widely described among Gram-negative bacteria and generally confer a multidrug resistance phenotype. Resistance integrons (RI) play an important role in the acquisition of antibiotic resistance. There are 3 main classes of RI. Class 3 RI has been poorly studied class with less than ten fully IR3 characterized. Objectives of this thesis were (i) to conduct an epidemiological study of class 3 RI in France and Cameroon and (ii) to better understand the modes of expression of the integrase and cassettes of IR3. We described 3 new class 3 RI isolated from environmental bacteria belonging to genus Aeromonas, Acinetobacter and Citrobacter. Gene cassettes encoded resistance to betalactams, aminoglycosides and quaternary ammonium compounds. We also described IR3 from three Delftia strains (2 D.acidovorans and 1 D.tsuruhatensis) in Africa containing cassettes that do not encode antibiotic resistance. The fundamental part of the work showed that the PintI3(1) promoter is involved in the expression of the intI3 gene. Furthermore, we demonstrated that variants of the Pc promoter and variants of the PintI3(1) promoter are functional with different strengths. These results showed that the environment may constitute a reservoir of class 3 integrons and that these genetic elements could play an important role in the spread of the resistance in this ecosystem
Intégrons de classe 3 : aspects mécanistiques et épidémiologiques
Get PDFIntegrons are bacterial genetic elements able to capture and express genes embedded within gene cassettes. They are widely described among Gram-negative bacteria and generally confer a multidrug resistance phenotype. Resistance integrons (RI) play an important role in the acquisition of antibiotic resistance. There are 3 main classes of RI. Class 3 RI has been poorly studied class with less than ten fully IR3 characterized. Objectives of this thesis were (i) to conduct an epidemiological study of class 3 RI in France and Cameroon and (ii) to better understand the modes of expression of the integrase and cassettes of IR3. We described 3 new class 3 RI isolated from environmental bacteria belonging to genus Aeromonas, Acinetobacter and Citrobacter. Gene cassettes encoded resistance to betalactams, aminoglycosides and quaternary ammonium compounds. We also described IR3 from three Delftia strains (2 D.acidovorans and 1 D.tsuruhatensis) in Africa containing cassettes that do not encode antibiotic resistance. The fundamental part of the work showed that the PintI3(1) promoter is involved in the expression of the intI3 gene. Furthermore, we demonstrated that variants of the Pc promoter and variants of the PintI3(1) promoter are functional with different strengths. These results showed that the environment may constitute a reservoir of class 3 integrons and that these genetic elements could play an important role in the spread of the resistance in this ecosystem.Les intégrons sont des supports génétiques bactériens de capture, d’expression et de dissémination de gènes de résistance aux antibiotiques sous forme de cassettes. Ils sont majoritairement décrits chez les bactéries à Gram négatif chez qui ils confèrent généralement un phénotype de multirésistance. Les intégrons de résistance (IR) jouent un rôle majeur dans l’acquisition de la résistance dans le monde bactérien. Il existe 3 principales classes d’IR ; les IR de classe 1, les IR de classe 2 et les IR de classe 3 (IR3). Contrairement aux 2 premières classes, les IR3 représentent la classe d’intégrons de résistance la moins étudiée. Très peu de travaux s’intéressent à leur étude et on dénombre actuellement moins de 10 IR3 entièrement caractérisés. Les objectifs de ce travail de thèse étaient (i) d’effectuer une étude épidémiologique des IR3 en France et au Cameroun et (ii) d’étudier les modalités d’expression de l’intégrase et des cassettes de ces intégrons. Nos travaux ont permis d’isoler puis de décrire 3 nouveaux IR3 présents au sein de bactéries environnementales appartenant aux genres Aeromonas, Acinetobacter et Citrobacter. Les cassettes de ces IR3 codent des résistances aux bétalactamines, aminosides et ammoniums quaternaires. De plus, nous avons caractérisé des IR3 dans 3 souches de Delftia spp. (2 D.acidovorans et 1 D. tsuruhatensis) isolées en Afrique ; les cassettes de ces intégrons ne codent pas de résistance aux antibiotiques. L’axe plus fondamental de ce travail de thèse a permis de montrer que le PintI3(1) est le promoteur impliqué dans l’expression du gène intI3. De plus, nous avons montré que les variants du promoteur Pc, ainsi que les variants du promoteur PintI3(1) sont fonctionnels et de force différente. Il ressort de nos travaux que l’environnement constituerait un réservoir d’intégrons de classe 3 et que ces supports génétiques pourraient jouer un rôle important dans la dissémination de la résistance au sein de cet écosystème
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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