1,720,965 research outputs found
Cefotaxime, des-cefotaxime and ceftazidime: In vitro activity and stability to hydrolysis from TEM-derived extended spectrum β-lactamases
No full textβ-lactams represent one of the most important class of antibiotics for the treatment of infectious diseases due to pathogenic bacteria. The selective pressure exerted from the wide spread use of third generation cephalosporins generated mutant β-lactamases belonging mainly to the TEM or SHV family that are able to extend the activity spectrum of hydrolysis. Moreover, extended spectrum cephalosporins are often a good choice in clinical practice towards Enterobacteriaceae. Here we report a comparative analysis of stability between cefotaxime, desacetyl-cefotaxime and ceftazidime with some common TEM-derivatives extended spectrum β-lactamases
Ceftaroline in vitro activity against methicillin-resistant Staphylococcus aureus and coagulase-negative Staphylococci: a short report from Italy
No full textHigh specificity of cphA-encoded metallo-β-lactamase from Aeromonas hydrophila AE036 for carbapenems and its contribution to β-lactam resistance
No full textThe Aeromonas hydrophila AE036 chromosome contains a cphA gene encoding a metallo-β-lactamase highly active against carbapenem antibiotics. This enzyme was induced in strain AE036 to the same extent by both benzylpenicillin and imipenem. When the cphA gene was inserted into plasmid pACYC184, used to transform Escherichia coli DH5α, the MICs of imipenem, meropenem, and penem HRE664 for recombinant clone DH5α(pAA20R), expressing the Aeromonas metallo-β-lactamase, were significantly increased, but those of penicillins and cephalosporins were not. When the metallo-β-lactamase purified from E. coli DH5α(pAA20R) was assayed with several β-lactam substrates, it hydrolyzed carbapenems but not penicillins or cephalosporins efficiently. These results demonstrate that this metallo-β-lactamase possesses an unusual spectrum of activity compared with all the other class B enzymes identified so far, being active on penems and carbapenems only. This enzyme may thus contribute to the development of resistance to penems and carbapenems but not other β-lactams
Ceftazidime and aztreonam resistance in Providencia stuartii: Characterization of a natural TEM-derived extended-spectrum β-lactamase, TEM-60
No full textA plasmid-encoded β-lactamase produced from a clinical strain of Providencia stuartii has been purified and characterized. The gene coding for the β-lactamase was cloned and sequenced. It appears to be a new natural TEM-derived enzyme, named TEM-60. Point mutations (Q39K, L51P, E104K, and R164S) are present with respect to the TEM-1 enzyme; the mutation L51P has never been previously reported, with the exception of the chromosomally encoded extended-spectrum β-lactamase PER-I. Kinetic parameters relative to penicillins, cephalosporins, and monobactams other than mechanism-based inactivators were related to the in vitro susceptibility phenotype
An in vitro investigation of levofloxacin and ciprofloxacin against clinical isolates of Pseudomonas aeruginosa
No full textIn vitro activity of cefodizime (HR-221) in combination with β-lactamase inhibitors
No full textCefodizime (formerly HR221) was tested either for in vitro microbiological activity or for its stability to β-lactamases in the presence of two β- lactamase inhibitors (clavulanic acid, tazobactam). Cefodizime was a poor substrate of class C enzymes but hyperproducer strains were generally resistant with or without a β-lactamase inhibitor used in combination. On the contrary, class A enzymes were able to hydrolyze cefodizime. However, strains expressing class A β-lactamase were susceptible to cefodizime in combination with clavulanic acid
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
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