1,721,146 research outputs found
Complete sequences of IncHI1 plasmids carrying blaCTX-M-1 and qnrS1 in equine Escherichia coli provide new insights into plasmid evolution
No full textObjectives: To determine the structure of two multidrug-resistant IncHI1 plasmids carrying blaCTX-M-1 in Escherichia coli isolates disseminated in an equine clinic in the Czech Republic. Methods: A complete nucleotide sequencing of 239 kb IncHI1 (pEQ1) and 287 kb IncHI1/X1 (pEQ2) plasmids was performed using the 454-Genome Sequencer FLX system. The sequenceswere compared using bioinformatic tools with other sequenced IncHI1 plasmids. Results: A comparative analysis of pEQ1 and pEQ2 identified high nucleotide identity with the IncHI1 type 2 plasmids. A novel 24 kb module containing an operon involved in short-chain fructooligosaccharide uptake and metabolism was found in the pEQ backbones. The role of the pEQ plasmids in the metabolism of shortchain fructooligosaccharides was demonstrated by studying the growth of E. coli cells in the presence of these sugars. The module containing the blaCTX-M-1 gene was formed by a truncated macrolide resistance cluster and flanked by IS26 as previously observed in IncI1 and IncN plasmids. The IncHI1 plasmid changed size and gained the quinolone resistance gene qnrS1 as a result of IS26-mediated fusion with an IncX1 plasmid. Conclusions: Our data highlight the structure and evolution of IncHI1 from equine E. coli. A plasmidmediated sugar metabolic element could play a key role in strain fitness, contributing to the successful dissemination and maintenance of these plasmids in the intestinal microflora of horses. © The Author 2014
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
Characterization of plasmids encoding extended-spectrum β-lactamases (ESBLs) and QnrS1 in Avian Pathogenic Escherichia coli (APEC) isolated from commercial poultry flocks in Italy.
No full textAvian pathogenic Escherichia coli (APEC) cause infections with high morbidity and mortality in poultry flocks. The aim of this study was to characterize the mobilizable pool mediating resistance to cephalosporins and fluoroquinolones in APEC collected in Italy between 2008 and 2012.
Non-repetitive APEC from turkeys (n=109), broilers (n=98) and layers (n=22) were examined. Isolates resistant to third-generation cephalosporins were screened for presence of blaTEM, blaSHV, blaCTX-M and blaCMY-2 and for chromosomal ampC promoter mutations, while all isolates were tested by PCR for all known plasmid-mediated quinolone resistance (PMQR) genes. ESBL/AmpC or PMQR-harboring plasmids were typed by traditional typing methods.
Twenty-eight (12%) isolates displayed resistance to third-generation cephalosporins either mediated by mutations leading to chromosomal ampC overproduction (n=10) or by the following plasmid/gene combinations: IncI1/ST26/blaSHV-12 (n=1), IncI1/ST3/blaCTX-M-1 (n=7), IncI1/ST26/blaCTX-M-1 (n=1), IncI1/ST36/blaCTX-M-1 (n=2), IncI1/STnew/blaCTX-M-1 (n=1), IncN/blaCTX-M-1 (n=1), IncI1/ST26/blaCTX-M-2 (n=1), IncFII/blaCTX-M-14 (n=1), IncK/blaCTX-M-14 (n=1), IncI1/ST26/blaCMY-2 (n=1) and IncK/blaCMY-2 (n=1). Plasmids measured approximately 40 to 200 kb and mainly exhibited different RFLP profiles. Sixty (26%) and 21 (9%) isolates displayed resistance to nalidixic acid and ciprofloxacin, respectively. qnrS1 was detected in two isolates on IncX2 and a non-typeable plasmid of ca. 30 and 40 kb, respectively.
The APEC population in Italian poultry harbours diverse ESBL-encoding genes and plasmids, often in association with fluroquinolone resistance. Interestingly, IncI1/ST26 plasmids were associated with four β-lactamases (SHV-12, CTX-M-1, CTX-M-2 and CMY-2), suggesting that this plasmid lineage is well adapted in APEC isolated from Italian poultry production. These findings underline the need to develop new strategies for prevention and therapy of multidrug-resistant APEC infections
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