1,720,965 research outputs found
Innovative strategies to detect antibiotic resistance in food sector
No full textAntibiotic resistance is a rapidly growing global issue that poses significant threats to animal and human health. This Ph.D. thesis aimed to determine the presence of antibiotic-resistant bacteria in raw food materials and to develop a rapid and low-cost method for detecting antibiotic resistance genes. The research focuses on two key bacterial species, Staphylococcus aureus and Escherichia coli and addresses the same topics in parallel for both microorganisms, as major contributors to antibiotic resistance, selected due to their presence in hospitals and agri-food chain.
The bacteria were isolated from raw cow milk, raw pork and beef meat that can act as vehicles for transmission of resistant bacteria to humans. Currently, the most widely used method for identifying antibiotic resistance is the gold standard antibiotic susceptibility test which involves isolation of the microorganism and exposure to specific antibiotics. Based on this technique, S. aureus isolates showed high levels of resistance to ampicillin, cefoxitin and tetracycline, while E. coli isolates to ampicillin. Since the bacterial cell surface is the primary interface with the surrounding environment and human host cells, and alterations in surface properties can impact both antibiotic susceptibility and virulence, the relation between antibiotic resistance in S. aureus isolates, bacterial cell surface characteristics and the interaction with human Caco-2 intestinal epithelial cell line were investigated. Multi-drug-resistant S. aureus did not show toxicity against Caco-2, but modified their surface, such as reducing permeability to block antibiotic entry or altering their surface charge. These findings underscore the need for further research to fully understand the risks associated with foodborne S. aureus, particularly its capability to evade antibiotic treatment and adapt its surface properties. Although effective, these methods required several days to provide results and were costly. To improve the detection of resistant genes, molecular techniques were employed to identify the most prevalent genes responsible for methicillin-resistance (mecA gene), tetracycline-resistance (tetK gene) and β-lactam-resistance (blaTEM gene). PCR and multiplex PCR were applied to isolates’ DNAs for the detection of target genes providing results within a few hours. These methods require specialized laboratories and expert operators and often the time before obtaining results is still high, in fact, the first hours from the infection are the critical ones for identifying the presence of resistance and choosing the appropriate therapy. Biosensors offered a promising solution to reduce costs and speed up the analysis. These innovative, small-size devices combine a recognition element for detecting the target with an electronic component for signal transduction. Biosensors are versatile, compact, fast, easy to use and ideal for self-testing systems and in situ applications, providing a faster and more accessible approach to detect antibiotic resistance. In this project, DNA sequences of mecA, tetK and blaTEM genes were used as templates to design single-stranded DNA probes, which worked as the recognition element for the biosensor. The probes were evaluated in silico using AmplifX, OligoAnalyzer and BLAST (Basic Local Alignment Search Tool) programs for their specificity further confirmed through dot blot testing. These newly designed probes were successfully applied in an electrochemical genosensor, allowing the detection of mecA, tetK and blaTEM genes in 20 minutes on the isolates’ DNAs.
Optimization of both dot blot and biosensor protocols was crucial for improving their practical application, in fact, lastly, these methods were directly applied to the whole DNA extracted from food matrices with promising results on their effectiveness
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
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