1,720,958 research outputs found
Effect of upstream regulatory regions and growth conditions on erm(B)-mediated constitutive MLS resistance in Group A streptococci
No full textObjective: The upstream sequence of the gene is considered a key factor in the translational control of erm expression, which can lead to either a constitutive (cMLS) or an inducible (iMLS) macrolide, lincosamide, and streptogramin B resistance phenotype. We observed that some GAS expressing a cMLS phenotype and harbouring erm(B) did not show a constant phenotype. The present work sought to study the relationship occurring between this phenotypic instability and the sequence context of the erm(B).
Methods: cMLS phenotype of five GAS clinical isolates was studied by growth in liquid medium using cells induced by preincubation with ERY (0.1 mg/L) followed by challenge with either josamycin (JOS) or clindamycin (CLI) (both at 50 mg/L) in supplemented Muller-Hinton II (MH). All cultures were incubated at 35–37oC in 5% CO2 for a maximum of 24 h. The effect of inoculum preparation (broth culture or direct colony suspension) was also evaluated.
The sequence of the erm(B) regulatory regions were determined following standard procedures and the general characteristics of the genetic elements harbouring erm(B) were determined using PCR.
Results: When inoculum was prepared by direct colony suspension, both CLI and JOS resistance of 3 strains was induced during the logarithmic phase of growth (i-cMLS). When the inoculum was prepared by the growth method, the same set of strains were insensible to the induction of CLI and JOS resistance but were susceptible to both antibiotics until the end of the logarithmic phase.
In these strains, the upstream regulatory sequences and the genetic context surrounding erm(B) were identical. A fourth strain had the same genetic characteristics of the i-cMLS strains but showed a constitutive MLS resistance in all the tested growth conditions, as well as a cMLS strain used as reference, the latter having a consistent deletion of the upstream regulatory region of the erm(B).
Conclusions: In GAS, the expression of erm(B)-mediated MLS resistance strongly depends on growth conditions. The contribution of erm(B) specific sequences seems to play a secondary role
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
Detection of phage-associated virulence/resistance genes in induced prophages of Streptococcus pyogenes clinical isolates
No full textObjectives: The genome of each sequenced Streptococcus pyogenes strain shows to contain many prophages encoding proven or putative extracellular virulence factors and antibiotic resistance determinants. In this work we determined the presence of prophage-associated virulence/resistance genes (F-vir) and the induction profile of prophages harbouring virulence/resistance genes in fifty-nine S. pyogenes pharyngeal isolates.
Methods: PCR was used to assess the presence of those genes (i.e. speA, speC, speH, speI, speK, speL, speM, ssa, spd1, spd3, spd4, sdn, sda, sla, mefA and TetO) known to be prophage-associated in S. pyogenes. Each strain was treated with mitomycin C to induce release of functional phages, and the corresponding unrestricted total DNA was then analysed by pulsed field gel electrophoresis (PFGE). S. pyogenes SF370 and strain-6 (mefA/TetO) were used as control strains. Single or multiple bands, corresponding to phage DNA, were obtained only in mitomycin treated cells. They were excised and analysed by PCR to detect the specific F-vir.
Results: Five percent of the strains did not contain any of the known F-vir, while 76% had at least two. The distribution of F-vir was greatly variable and the overall mean number of F-vir per isolate was 3.8 (± 2.3). The release of phage DNA was achieved in 17 strains. Among these, PCR analysis detected a single F-vir in the phage DNA released by 35.3% of the strains, and three F-vir in 17.6%. One strain released phage DNA containing two F-vir, whereas another strain released phage DNA positive to five F-vir. The F-vir most frequently associated with released phage DNAs were sdn, spd4, speC, spd1 and spd3.
Conclusion: The pharynx is colonised by S. pyogenes harbouring a variable number and assortment of F-vir. A limited number of virulence genes are hosted by functional prophages and, therefore, have the potentiality to be horizontally transferred. Many strains possess different important F-vir that, at least in the conditions used, cannot be detected in released phage DNAs. These results suggest that the population of Fvir-lacking functional prophages is vast and that the polylysogeny would be the product of the accumulation of temperate phages that eventually become defective
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
Distribution of phage-associated virulence genes in pharyngeal group a streptococcal strains isolated in Italy.
Full text linkThe presence and assortment of 16 known virulence/resistance genetic determinants carried by prophages or prophage-like elements were tested in 212 clinical group A Streptococcus (GAS) strains and related to available data from SmaI macrorestriction/pulsed-field gel electrophoresis analysis and emm typing. A strong correlation existed among the three analyses. This finding supports the substantial contribution to the evolution and diversification of the GAS genome attributed to phages
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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