1,721,010 research outputs found
Enterobacteriaceae resistant to carbapenems isolated in North Lebanon : mechanisms, genetic support and pathogenicity
No full textLes carbapénèmes sont des antibiotiques de la famille des β-lactamines utilisées en dernier recours à cause de leur stabilité vis-à-vis de la plupart des mécanismes de résistance. Cependant, on assiste chez les entérobactéries à l’émergence de carbapénèmases capables d’inactiver ces molécules. Les objectives de ce travail étaient d’explorer l’émergence de ces mécanismes de résistance dans des entérobactéries isolées au Nord Liban entre 2008 et 2012, d’analyser leur support génétique, ainsi que le fond génétique et la pathogénicité des souches porteuses. Nous avons observé une augmentation d’un facteur quatre de la prévalence des entérobactéries de sensibilité diminuée ou résistantes aux carbapénèmes dans les prélèvements cliniques hospitaliers entre 2008 et 2012. Un portage intestinal a été également observé chez 1,5% des individus dans une population d’enfants issus de la communauté. Le phénotype de résistance observé était lié à la production de la carbapénèmase OXA-48. Bien que sept espèces productrices ont été identifiées, la plupart des isolats étaient des souches non-redondantes appartenant aux espèces K. pneumoniae et surtout E. coli. Le vecteur de la diffusion de OXA-48 dans ces bactéries était trois plasmides du groupe d’incompatibilité IncL/M de 49 kb, 63 kb et 84 kb. Cependant, 67% des souches E. coli portaient le gène codant OXA-48 (blaOXA-48) sur le chromosome. La caractérisation des supports génétiques par des approches de séquençage à haut débit a montré qu’ils étaient apparentés et le produit de remaniements génétiques impliquant le transposon Tn21-like, la séquence d'insertion IS1R ou un nouveau transposon composite appelé Tn6237. L’insertion chromosomique de blaOXA-48 résultait de la transposition de Tn6237 qui est capable de transférer un fragment plasmidique de 20 kb dans différents sites du chromosome de E. coli. Les souches K. pneumoniae produisant OXA-48 n’appartenaient pas aux génotypes capsulaires hautement virulents K1 et K2, mais portaient des facteurs identifiées pour favoriser la virulence ou la colonisation de l’hôte. OXA-48 a été observée dans tous les phylogroupes de E. coli, y compris les phylogroupes B2 et D connus pour contenir les souches pathogènes extra-intestinales. Une souche se distinguait par une accumulation sans précédent de huit îlots de pathogénicité. Cette souche induisait une létalité inhabituellement élevée dans un modèle murin de sepsis. En conclusion, l’acquisition du gène blaOXA-48 est donc liée à la diffusion de plasmides apparentés, qui sont marqués par une plasticité conduisant à une localisation chromosomique du gène pouvant favoriser sa persistance. Elle conduit à une diffusion multi-clonale de souches K. pneumoniae et surtout E. coli potentiellement hautement virulentes. Cette association entre de l’espèce E. coli et la carbapénèmase OXA-48 est inquiétante, car E. coli constitue à la fois un réservoir dont la taille peut être considérable et un pathogène responsable d’infections fréquentes pouvant parfois mettre en jeu le pronostic vital.In the β-lactam family, carbapenems are the most effective antimicrobial agents used as a last resort due to their stability toward most resistance mechanisms. However, we recently observed the emergence of carbapenemase-producing Enterobacteriaceae. The aim of the present study consisted to explore (i) the epidemiological situation of carbapenem-resistant Enterobacteriaceae isolated in North Lebanon between 2008 and 2012, (ii) the identification of the resistance mechanisms, and (iii) the characterization of pathogenicity and genetic background of the corresponding strains. We observed a 4-fold increase in the prevalence of Enterobacteriaceae exhibiting decreased susceptibility or resistance to carbapenems in the clinical isolates collected at hospital during 2008-2012. The prevalence of fecal carriage of carbapenemase-producing Enterobacteriaceae was estimated to 1.5% in healthy children of the community. OXA-48 was the only carbapenemase identified among non-redundant isolates which spread to seven species. E. coli and K. pneumoniae were the main represented species. The OXA-48-encoding gene (blaOXA-48) was carried by three novel IncL/M plasmids of 49 kb, 63 kb and 84 kb. However, 67% of E. coli strains encoded blaOXA-48 chromosome-mediated. The sequencing of the previously mentioned genetic structures by high -throughput approaches showed that they are the product of genetic rearrangements involving the Tn21-like transposon, the insertion sequence IS1R and a novel composite transposon designed Tn6237. The chromosomal insertion of blaOXA-48 was due to the acquisition of element Tn6237 leading consequently to the transposition of 20 kb plasmid fragment into different sites of E. coli chromosome. The pathogenicity profile of K. pneumoniae strains showed that they did not belong to highly virulent capsular genotypes K1 and K2, but harbored factors promoting virulence and host colonization. E. coli isolates belonged to different phylogroups, including phylogroups B2 and D known to contain the extra-intestinal pathogenic strains. An E. coli strain was characterized by a broad accumulation of pathogenicity islands (n=8). In addition, this strain induced an unusually high lethality in a mouse model of sepsis. In conclusion, the acquisition of the blaOXA-48 gene is linked to the spread of related IncL/M plasmids, which are marked by a plasticity leading to a chromosomal location of blaOXA-48 and probably promoting its persistence. It leads to a multiclonal diffusion of K. pneumoniae and especially E. coli potentially highly virulent. This association between E. coli and the carbapenemase OXA-48 is worrying because E. coli represent a putative important reservoir and a pathogen agent responsible for frequent infections that can be a life threatening
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
Emerg Infect Dis
No full textWe recovered 2 carbapenem-resistant K2-ST86 hypermucoviscous Klebsiella pneumoniae isolates from patients in France. The isolates had genetic attributes of hypervirulent K. pneumoniae but differed in ability to cause mouse lethality. Convergence of hypervirulent K. pneumoniae toward resistance could cause a health crisis because such strains could be responsible for severe and untreatable infections
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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