1,721,125 research outputs found
Interplay between uropathogenic Escherichia coli and bladder cells and new strategies to counteract bacterial persistence
Full text linkUrinary tract infections (UTIs) are the most frequent community and hospital-acquired infections. Uropathogenic Escherichia coli (UPEC) is the major causative agent of UTIs. The high level of recurrences, in which a single bacterial strain causes two or more consecutive UTIs, strongly suggests a reservoir within host. UPEC strains can invade epithelial cells of the urinary tract and replicate to form intracellular bacterial communities (IBCs) with biofilm-like properties, and may persist acting as quiescent intracellular bacterial reservoirs (QIRs). The formation of these structures represents a key event in the development of recurrences and is associate with the failure of conventional antibiotic therapies. The most crucial factor for the persistence of UTIs is the biofilm formation ability of UPEC, which protects them against harmful conditions, antimicrobial agents, and the host's immune system. Nanotechnology has been presented as a promising approach to enhance the activity of antimicrobial agents. The use of drug-delivery systems has been hypothesized for the controlled and localized release of drugs even in the case of multi-resistant bacteria and in the fight against biofilm. In order to identify bacterial characteristics possibly associated with recurrence of the infection, in this study UPEC strains, isolated from patients with recurrent UTIs, were sequenced, phenotypically and genotypically characterized, and assayed for invasion and survival ability in cell models. To explore new strategies able to induce bacterial clearance, the activity of niosomes (Nio) loaded with gentamicin (GM) was evaluated against intracellular bacteria and Nio, loaded with ciprofloxacin (CIP), was assayed for the capacity to inhibit biofilm formation. UPEC collected from patients suffering from recurrent UTIs and reference strains were used. The whole genome was performed on Illumina platform. Profiles relative to resistance genes, virulence factors, and multilocus sequence typing were determined by querying genomes against dedicated databases. The isolates were phenotypically characterized and assayed to adhere, invade, and persist in bladder cells (T-24 ATCC HTB-4) by gentamicin protection assay. ROS accumulation and interleukins production in T24 cells after UPEC infection, were detected. Empty and antibiotics loaded Nio were prepared and were characterized in term of stability and drug entrapment efficiency. To evaluate potential antiinvasive activity, non-cytotoxic and non-bactericidal concentrations of GM-Nio were added during the UPEC infection in the bladder. Furthermore, to verify the effect of CIP-Nio on biofilm production, bacterial strains were treated with niosomal preparations for 24 h. Ultrastructural biofilm modifications were visualized by Scanning Electron Microscopy (SEM). Genotypic characterization of the strains evidenced an heterogenous virulence factor profile. UPEC strains were moderate or strong biofilm producers, non-haemolytic and belonged to phylogroup D and B2. UPEC strains were able to efficiently adhere and invade, but not survive inside T24 cells. UPEC infection promoted the production of ROS but not all strains were able to induce interleukin production in bladder cells. Nio showed nanometric dimensions and a good stability profile and when loaded with antibiotics, significantly inhibited bacteria viability. Antibiotic delivered by Nio decreased UPEC invasion into bladder cells and efficiently inhibit the biofilm formation. UPEC genome is a mosaic continuum and no single feature can be used to differentiate strains. Similarly, no virulence factor alone is sufficient to cause disease. The complex interplay between bacterial infection capabilities, treatment success and host factors are likely to determine recurrence rather than specific genetic characteristics of the E. coli bacteria itself. Further studies exploring host-pathogen relationships and impact of QIR formation with organoid models in RUTI pathogenesis should be performed to contribute to translation of these results into innovative treatments
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
Electric effects induced by artificial seismic sources at Somma-Vesuvius volcano
No full textIn this paper, we present a series of self-potential measurements at Somma-Vesuvius volcanic area acquired in conjunction with an active seismic tomography survey. The aim of our study is both to provide further confirmation to the occurrence of seismo-electric coupling and to identify sites suitable for self-potential signal monitoring at Somma-Vesuvius district. The data, which were collected along two perpendicular dipoles, show significant changes on the natural electric field pattern. These variations, attributable to electrokinetic processes triggered by the artificial seismic waves, were observed after explosions occurred at a distance less than 5 km from the SP dipole arrays. In particular, we found that the NW-SE component of the natural electric field was more sensible to the shots than the NE-SW one, and the major effects did not correspond to the nearest shots. Such evidences were interpreted considering the underground electrical properties as deduced by previous detailed resistivity and self-potential surveys performed in the study area
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