1,721,088 research outputs found
Antimicrobial resistance islands: resistance gene clusters in Salmonella chromosome and plasmids
No full textGenes conferring simultaneous resistance to different classes of antimicrobials, confer a selective advantage to the host, particularly when those corresponding antibiotics are administered. Multiple resistance genes clustered within the same genetic locus (resistance island) can be transferred en bloc to other organisms. In this chapter we review novel multidrug resistance islands recently described in Salmonella. © 2006 Elsevier SAS. All rights reserved
The C-terminal cytoplasmic tail of herpes simplex virus type 1 gE protein is phosphorylated in vivo and in vitro by cellular enzymes in the absence of other viral proteins
No full textHerpes simplex virus 1 glycoprotein E (gE-1) is highly phosphorylated in culture cells during infection. In this report, it is shown that phosphorylation is mediated by host enzymes in human cells stably transfected with gE, in the absence of other herpesvirus products. In contrast, a tailless gE product (C terminus deletion mutant) is not phosphorylated. By using an in vitro kinase assay combined with linker-insertion mutagenesis, it is shown that casein kinase II catalyses the phosphorylation of the C-terminal domain of the protein. Also, it is demonstrated that the serine residues at positions 476 and/or 477 in the cytoplasmic portion of the protein are the major accepters for the phosphate groups
Sources of diversity of carbapenem resistance levels in Klebsiella pneumoniae carrying blaVIM-1
No full textObjectives: To elucidate the mechanisms responsible for the diversity of β-lactam resistance phenotypes among isolates of a VIM-1-producing Klebsiella pneumoniae (VPKP) strain that is endemic in Greek hospitals. Methods: Five VPKP clinical isolates were studied. MICs of β-lactams were determined by agar dilution. PFGE of Xba I-digested genomic DNA was used for typing. Profiles of outer membrane proteins (OMPs) were determined by SDS-PAGE. Selected isolates were transformed with a plasmid encoding the Omp36K porin. β-Lactamase activities were analysed by IEF and imipenem hydrolysis was assessed by spectrophotometry. VIM-1-encoding, self-transmissible plasmids were characterized by replicon typing, RFLP and hybridization with bla VIM - and IS26-specific probes. Characterization of integrons was performed by PCR, cloning and sequencing. Results: Isolates exhibited highly similar PFGE patterns. Imipenem MICs were 2, 4, 16, 32 and 64 mg/L. The isolate with the highest imipenem MIC (Vipm-64) lacked a 36 kDa OMP. Expression of a cloned OmpK36 in this isolate reduced the imipenem MIC to susceptibility levels. Imipenem-hydrolysing activity was significantly higher in Vipm-16 as compared with the other isolates that expressed similar amounts of VIM-1. All isolates transferred β-lactam resistance to Escherichia coli through conjugative, IncN plasmids that exhibited differences in the RFLP and hybridization patterns with bla VIM - and IS 26 -specific probes. The Vipm-16 plasmid, mediating the higher imipenem MICs among transconjugants, carried two copies of bla VIM-1. Cloning and sequencing showed In-e541-like integrons truncated at the 5′CS by insertion of IS 26 elements at two different positions. Conclusions: A VIM-1-producing strain of K. pneumoniae has evolved through OMP alterations and rearrangements in the bla VIM-1-carrying plasmid probably mediated by IS 26, generating isolates with imipenem MICs ranging from susceptibility to resistance. © 2006 Oxford University Press
IS26-associated In4-type integrons forming multiresistance loci in enterobacterial plasmids
No full textThree distinct multiresistant loci from enterobacterial plasmids each comprised an integron and an IS26-associated sequence. Sequence comparison suggested a common ancestral structure that derived from an IS26 insertion into the 5′ conserved segment of an In4-type integron and evolved through acquisition of gene cassettes and IS26-mediated recruitment of additional resistance genes of diverse origin. Copyright © 2005, American Society for Microbiology. All Rights Reserved
Expression of the herpes simplex virus type 1 glycoprotein E in human cells and in Escherichia coli: Protection studies against lethal viral infection in mice
No full textThe objective of this study was to examine the protective efficacy of purified recombinant herpes simplex virus type 1 (HSV-1) glycoprotein E (gE-1) in the mouse lethal challenge model. A secreted form of gE-1 (hgE-1s) protein, containing amino acids 1-406, was produced in human cells by using the episomal replicating pRP-RSV expression vector. In addition, a portion of the gE-1 (bgE-1t) protein corresponding to amino acids 90-406, was expressed in Escherichia coli as a fusion protein with maltose binding protein using the pMAL-c2 expression vector. Mice vaccinated with hgE-1s developed high serum titres of HSV-1-neutralizing antibodies and were significantly protected from intraperitoneal lethal HSV-1 challenge, whereas mice vaccinated with bgE-1t exhibited only moderate levels of protective immunity. These results demonstrate that the expression of gE-1 in human cells has a strong impact on its protective efficacy and that most importantly the hgE-1s protein could be of value as a component of an HSV multi-subunit vaccine
Escherichia coli expressed herpes simplex virus gG1 and gG2 proteins in ELISA and immunoblotting assays
No full textThe type 1 and type 2 glycoprotein G (gG1 and gG2) of herpes simplex virus (HSV) were expressed in Escherichia coli as fusion proteins with the maltose binding protein (MBP) using the pMAL-c2 expression vector. The MBP-gG1 fusion protein contains all but the four amino acids from the amino-terminus of gG1, whereas the MBP-gG2 fusion protein was missing the first 30 amino acids that comprise the signal peptide of the protein. The diagnostic value of these antigens was examined by two methods: (1) immunoblot assay based on MBP-gG1 and MBP-gG2 fusion proteins present in crude E. coli cell extracts and (2) enzyme-linked immunosorbent assay (ELISA) of immunoaffinity-purified recombinant MBP-gG1 and MBP-gG2 fusion proteins. Of 28 serum samples known to have antibody to HSV-1 (10 specimens positive for HSV-1 alone and 18 specimens positive for mixed antibody to HSV-1/HSV-2), 27 were reactive to the MBP-gG1 recombinant protein both in ELISA and in immunoblotting. In addition, of 20 serum samples known to have antibody to HSV-2 (2 specimens positive for HSV-2 alone and 18 samples positive for mixed antibody to HSV-1/HSV-2), 15 were found to be reactive to the MBP-gG2 recombinant protein by ELISA and 16 by immunoblotting. None of the 13 HSV-antibody-negative serum samples showed reactivity to the MBP-gG1 or MBP-gG2 antigens by either assay. Moreover, none of the serum samples known to have antibody to HSV-1 alone showed reactivity to the MBP-gG2 recombinant antigen. This study verified the potential application of the E. coli-expressed recombinant gG1 and gG2 proteins as diagnostic antigens and demonstrated the MBP fusion system to be a simple and effective method of producing adequate amounts of low-cost, easily purified gG antigens
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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