1,721,020 research outputs found
Replicon sequence typing of IncF plasmids carrying virulence and resistance determinants
No full textObjectives: IncF plasmids are frequently encountered in clinical enterobacterial strains associated with the dissemination of relevant antimicrobial resistance and virulence genes. These plasmids are usually heterogeneous in size and carry multiple replicons, and technical difficulties can impair the comparison and detection of related plasmids by restriction fragment length polymorphism analysis. We devised a rapid sequence-based typing scheme to categorize the members of this plasmid family into homogeneous groups. Methods: We compared the available IncF replicon sequences, identifying the combination of the different IncF replicon alleles as the discriminating characteristic of these plasmid scaffolds. An IncF typing method based on PCR amplification and sequence typing of the IncF replicons was devised. A collection of IncF plasmids carrying resistance and/or virulence genes, identified in strains from different sources and geographical origins, was tested with this typing system. Results: We devised a replicon sequence typing (RST) scheme discriminating IncF plasmid variants. This system was tested on the collection of IncF plasmids, demonstrating that it was useful for the discrimination of plasmids carrying the same resistance gene (i.e. the blaCTX-M-15 gene), but also recognized strictly related virulence plasmids (i.e. IncFIme plasmids). The PCR-based replicon typing (PBRT) system was also updated by including new primer pairs to allow the identification of the Salmonella, Klebsiella and Yersinia IncF plasmids. Conclusions: The ability to recognize and sub-categorize IncF plasmids by RST in homogeneous groups on the basis of their phylogenetic relatedness can be helpful in analysing their distribution in nature and discovering their evolutionary origin. © The Author 2010. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved
Inhibition of HIV-1 transcription by cyclopentenone prostaglandin A1 in Jurkat T lymphocytes
No full textCyclopentenone prostaglandins inhibit virus replication in several DNA and RNA virus models. In this report we investigated the effect of prostaglandin A1 (PGA1) on HIV-1 transcription in human CD4+ Jurkat T lymphocyte cells. A dramatic reduction of HIV-1 RNA levels was detected up to seven days post infection in both unstimulated and phorbol 12-mystrate 13-acetate (PMA)-stimulated cells treated with PGA1. PGA1 treatment of cells was also effective in inhibiting the transcription of a chloramphenicol acetyltransferase (CAT) reporter gene, under the control of HIV-1 LTR, in Jurkat-Tat cells. We also show that PGA1 induced the synthesis of 70-kDa heat-shock protein (HSP70) in this cell system and the induction correlated with the drug-antiviral activity. PGA1 was also found to induce the loss of the tumor suppressor p53 protein, in the "proliferative" conformation, in a time correlation with the induction of the HSP70 As the "proliferative" p53 has been involved in the positive trans-activation of the HIV-1 LTR its depletion could contribute to the inhibitory mechanisms of PGA1 on virus transcription
Contemporary IncI1 plasmids involved in the transmission and spread of antimicrobial resistance in enterobacteriaceae
Full text linkIncI1 has become one of the most common plasmid families in contemporary Enterobacteriaceae from both human and animal sources. In clinical epidemiology, this plasmid type ranks first as the confirmed vehicle of transmission of extended spectrum beta-lactamase and plasmid AmpC genes in isolates from food-producing animals. In this review, we describe the epidemiology and evolution of IncI1 plasmids and closely related IncIγ plasmids. We highlight the emergence of epidemic plasmids circulating among different bacterial hosts in geographically distant countries, and we address the phylogeny of the IncI1 and IncIγ family based on plasmid Multilocus Sequence Typing. © 2018 Elsevier Inc
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
Multilocus sequence typing of IncI1 plasmids carrying extended-spectrum β-lactamases in Escherichia coli and Salmonella of human and animal origin
No full textObjectives: Plasmids belonging to incompatibility group I1 (IncI1) are widespread in Enterobacteriaceae and are characterized by the presence of a cluster of genes encoding the type IV pili, contributing to the virulence of Shiga-toxigenic Escherichia coli. Recently, IncI1 plasmids were identified in E. coli and Salmonella strains of animal origin as responsible for the dissemination of β-lactamase genes. Plasmid multilocus sequence typing (pMLST) was developed to discern naturally occurring IncI1 plasmids in homogeneous groups according to their allele assortment. Methods: pMLST was developed by selecting multiple target genes on the available complete IncI1 plasmid DNA sequences. Sixteen plasmids, all assigned to the IncI1 group by the PCR-based replicon typing method, were included in this study. They were analysed for β-lactamase genes and typed by restriction fragment length polymorphism (RFLP) and pMLST. Results: Sixteen plasmids identified in E. coli and Salmonella isolated from animals and humans in different countries carried blaCMY-2, blaCTX-M-15, blaCTX-M-1, blaCTX-M-14, blaTEM-52, blaSHV-12 or blaTEM-1 β-lactamase genes. These plasmids were classified by RFLP in nine different groups corresponding to the nine sequence types determined by pMLST. Conclusions: The pMLST method was suitable for rapid and easy subtyping of IncI1 plasmids. This study demonstrates that the pMLST method can contribute to the epidemiological description of circulation of specific resistance plasmids among β-lactamase producers isolated from animals and humans. © The Author 2008. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved
Plasmid-mediated quinolone resistance and β-lactamases in Escherichia coli from healthy animals from Nigeria
No full textObjectives: The animal reservoir of plasmid-mediated quinolone resistance (PMQR) and β-lactamases is still controversial and little information is available on the prevalence of these resistance determinants in developing countries. The aim of this study was to identify and characterize PMQR and β-lactamases in a collection of commensal ampicillin-resistant Escherichia coli isolated from healthy chickens and pigs at slaughter, collected in November-December 2006, in Ibadan, Nigeria. Methods: One hundred and sixty-two ampicillin-resistant E. coli were obtained from healthy chickens and pigs at slaughter in Ibadan, Nigeria. Strains were tested for antimicrobial susceptibility by disc diffusion assay. MICs of ciprofloxacin were determined by Etest. Resistance genes were screened by PCR and DNA sequencing. Clonal relatedness of the isolates was determined by enterobacterial repetitive intergenic consensus-PCR. Plasmids were transferred by conjugation and transformation and characterized by PCR-based replicon typing and plasmid multilocus sequence typing. Results: PMQR genes were detected in 18 E. coli strains; 11 of them showed reduced susceptibility to ciprofloxacin. Twelve strains carried qnrS1, three strains carried qnrB19, one strain carried qnrB10 and three strains carried qepA; one strain carried both qepA and qnrB10. All strains carried the blaTEM gene; one strain was positive for the CTX-M-15 extended-spectrum β-lactamase. Conclusions: Our findings suggest that food animals could represent an important reservoir of PMQR in this region of Africa. Previous studies reported high prevalence of qnr genes in clinical isolates from humans in Nigeria, suggesting that the spread of these resistance determinants in this country could be particularly relevant. © The Author 2011. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved
- …
