1,721,011 research outputs found
Virulence of MRSA USA300 is enhanced by sub-inhibitory concentration of two different classes of antibiotics.
No full textCommunity-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) USA300 is responsible of many kinds of infections of skin and soft-tissue. Antibiotic resistance, biofilm formation and the ability to adhere and invade are virulence factors that contribute to MRSA pathogenesis. In some cases, decreased bioavailability of antibiotics in systemic circulation could result; in these conditions sub-therapeutic levels of the antibiotics may be established, exposing bacteria to sub-inhibitory concentrations. On the basis of several published scientific data it is fair to assume that all these events could induce an increase of bacterial virulence. In the present study, we investigated this process by measuring the effects of low doses of two different classes of antibiotics on some virulence features of MRSA USA300 isolate, like the ability to adhere and invade eukaryotic cells. Results obtained strongly support the importance of the respect of a correct dosage of antibiotic in therapy to escape the insurgence of more virulent phenotypes
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
Bacterial acid phosphatase gene fusions useful as targets for cloning-dependent insertional inactivation
No full textThe Morganella morganii phoC gene, encoding a class A acid phosphatase, was used to generate gene fusions with modified amino-terminal moieties of the Escherichia coli lacZ gene carrying a multiple-cloning site flanked by phage-specific promoters and recognition sites for universal sequencing primers. The corresponding hybrid proteins retained a PhoC-like enzymatic activity which is easily detectable by a plate histochemical assay, rendering similar gene fusions potentially useful as targets for cloning-dependent insertional inactivation. Cloning experiments performed in plasmids carrying similar lacZ-phoC fusions confirmed their usefulness as cloning vectors for direct screening of recombinants. As compared to conventional lacZ α-complementation-based vectors, which can only be used in E. coli hosts carrying specific lacZ mutations, the lacZ-phoC fusion-based vectors can be used in combination with any E. coli host and require a less expensive histochemical assay for screening of recombinants, while retaining all the advantageous features that made the former so popular as general purpose cloning vehicles.
The Morganella morganii phoC gene, encoding a class A acid phosphatase, was used to generate gene fusions with modified amino-terminal moieties of the Escherichia coli lacZ gene carrying a multiple-cloning site flanked by phage-specific promoters and recognition sites for universal sequencing primers. The corresponding hybrid proteins retained a PhoC-like enzymatic activity which is easily detectable by a plate histochemical assay, rendering similar gene fusions potentially useful as targets for cloning-dependent insertional inactivation. Cloning experiments performed in plasmids carrying similar lacZ-phoC fusions confirmed their usefulness as cloning vectors for direct screening of recombinants. As compared to conventional lacZ α-complementation-based vectors, which can only be used in E. coli hosts carrying specific lacZ mutations, the lacZ-phoC fusion-based vectors can be used in combination with any E. coli host and require a less expensive histochemical assay for screening of recombinants, while retaining all the advantageous features that made the former so popular as general purpose cloning vehicles
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
Virulence of Pseudomonas aeruginosa in cystic fibrosis. Relationships between normoxia and anoxia lifestyle
Full text linkThe airways of cystic fibrosis (CF) patients are colonized by many pathogens and the most common is Pseudomonas aeruginosa, an environmental pathogen that is able to infect immunocompromised patients thanks to its ability to develop resistance to conventional antibiotics. Over 12% of all patients colonized by P. aeruginosa harbour multi-drug resistant species. During airway infection in CF, P. aeruginosa adopts various mechanisms to survive in a hostile ecological niche characterized by low oxygen concentration, nutrient limitation and high osmotic pressure. To this end, P. aeruginosa uses a variety of virulence factors including pigment production, biofilm formation, motility and the secretion of toxins and proteases. This study represents the first report that systematically analyzes the differences in virulence features, in normoxia and anoxia, of clinical P. aeruginosa isolated from CF patients, characterized by multi- or pan-drug antibiotic resistance compared to antibiotic sensitive strains. The virulence features, such as biofilm formation, protease secretion and motility, are highly diversified in anaerobiosis, which reflects the condition of chronic CF infection. These findings may contribute to the understanding of the real-world lifestyle of pathogens isolated during disease progression in each particular patient and to assist in the design of therapeutic protocols for personalized medicine
PHOSPHORYLCHOLINE IMPAIRS SUSCEPTIBILITY TO BIOFILM FORMATION OF HYDROGEL CONTACT LENSES
No full textPURPOSE: To compare silicone-hydrogel, poly(2-hydroxyethyl methacrylate) (pHEMA), and phosphorylcholine-coated (PC-C) contact lenses in terms of their susceptibility to biofilm formation by Staphylococcus epidermidis and Pseudomonas aeruginosa.
DESIGN: Laboratory investigation.
METHODS: Biofilm formation on colonized test lenses was evaluated with confocal microscopy and in vitro antibiotic susceptibility assays. The results of the latter assays were compared with those performed on planktonic cultures of the same organism.
RESULTS: For both microorganisms, sessile colonies on silicone-hydrogel and pHEMA lenses displayed lower antibiotic susceptibility than their planktonic counterparts. In contrast, the susceptibility of cultures growing on PC-C lenses was comparable with that for planktonic cultures. In particular, minimum inhibitory concentration for Tazocin (piperacillin plus tazobactam; Wyeth Pharmaceuticals, Aprilia, Italy; S. epidermidis) and gentamicin (P. aeruginosa) was identical, either in the presence of PC-C support or in planktonic cultures (Tazocin, </= 0.2 mug/ml; gentamicin, 0.4 mug/ml). Minimum inhibitory concentration for imipenem (P. aeruginosa) was two-fold higher for PC-C lenses (0.4 mug/ml) with respect to planktonic cultures (0.2 mug/ml). Confocal microscopy of lenses colonized for 24 hours with P. aeruginosa green fluorescent protein-expressing cells revealed a sessile colonization on silicone-hydrogel lens and a few isolated bacterial cells scattered widely over the surface of the PC-C lens.
CONCLUSIONS: An increase in antibiotic susceptibility of bacterial cultures was associated with diminished bacterial adhesion. Our results indicate that PC-C lenses seem to be more resistant than silicone-hydrogel and pHEMA lenses to bacterial adhesion and colonization. This feature may facilitate their disinfection
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