1,720,989 research outputs found
Caratterizzazione molecolare della resistenza ai chinoloni e al cloramfenicolo in Streptococcus Agalactiae
Full text linkLo studio ha analizzato la sensibilità ai chinoloni e al cloramfenicolo di 368 isolati clinici di Streptococcus agalactiae raccolti nel periodo 2010-2016 da tre ospedali della Regione Marche. La resistenza ai chinoloni è risultata pari al 2,99% (11 ceppi), mentre quella al cloramfenicolo è stata dell’1,6% (6 isolati). In 10 isolati la resistenza ad alto livello ai chinoloni era conferita da mutazioni delle regioni QRDR in entrambi i bersagli enzimatici GyrA (Ser81Leu) e ParC (Ser79Phe). Un unico isolato, mostrante la singola mutazione in ParC, era caratterizzato da una resistenza a basso livello. 4 degli 11 ceppi resistenti ai chinoloni erano resistenti anche al cloramfenicolo. La caratterizzazione genetica e gli esperimenti di trasferibilità hanno portato alla dimostrazione di un nuovo elemento genetico mobile (~110 kb) denominato ICESag236, che veicola i determinanti catQ, erm(TR) e mef(I), che conferiscono resistenza al cloramfenicolo e ai macrolidi. ICESag236 è un nuovo elemento genetico mosaico derivante dalla ricombinazione molecolare di ICESpn529IQ e ICESagTR7, identificati rispettivamente in Streptococcus pneumoniae e in S. agalactiae. I risultati ottenuti in questo studio confermano la grande flessibilità genomica di S. agalactiae. Inoltre, evidenziano come in questa specie la diffusione dell’antibiotico-resistenza può dipendere sia dalla circolazione di specifici cloni (resistenza ai chinoloni), sia dall’evoluzione di particolari elementi genetici (resistenza al cloramfenicolo).In this study 368 clinical isolates of Streptococcus agalactiae, collected in 2010–2016 from three hospitals of central Italy, were screened for quinolone and chloramphenicol resistance. The rate of quinolone resistance was 2,99% (11 strains), while chloramphenicol resistance rate was 1,6% (6 isolates). In 10 isolates the high-level quinolone resistance was conferred by mutations of the QRDR regions in both enzymatic targets GyrA (Ser81Leu) and ParC (Ser79Phe). An isolate, showing the single mutation in ParC, was characterized by a low-level resistance. Interestingly, 4 of the 11 quinolone-resistant strains were also resistant to chloramphenicol. Transferability assays and sequencing experiments led to the characterization of a new mobile genetic element (~110 kb) designated ICESag236, harbouring catQ, erm(TR) and mef(I) determinants, which confer resistance to chloramphenicol and macrolides. ICESag236 is a new mosaic genetic element resulting from recombination of two integrative and conjugative elements (ICEs) originally described in different streptococcal species: S. agalactiae ICESagTR7, and Streptococcus pneumoniae ICESpn529IQ. The results obtained in this study confirm the great genomic flexibility of S. agalactiae. Moreover, we show how in this species the diffusion of the antibiotic-resistance may depend both on the spread of specific clones (e.g. for resistance to quinolones), and on the evolution of peculiar genetic elements (e.g. for resistance to chloramphenicol)
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
A new mosaic integrative and conjugative element from Streptococcus agalactiae carrying resistance genes for chloramphenicol (catQ) and macrolides [mef(I) and erm(TR)]
No full textObjectives: To investigate the genetic basis of catQ-mediated chloramphenicol resistance in Streptococcus
agalactiae.
Methods: Two clinical strains of catQ-positive chloramphenicol-resistant S. agalactiae (Sag236 and Sag403) were
recently isolated, typed (MLST, PFGE pulsotypes, capsular types) and their antibiotic resistances investigated by
phenotypic and genotypic approaches. Several molecular methods (PCR mapping, restriction assays, Southern
blotting, sequencing and sequence analysis, conjugal transfer assays) were used to determine the genetic
context of catQ and characterize a genetic element detected in the isolates.
Results: Sag236 and Sag403 shared the same ST (ST19), but exhibited a different capsular type (III and V,
respectively) and pulsotype. Both harboured the macrolide resistance genes mef(I) and erm(TR) and the
tetracycline resistance gene tet(M). Accordingly, they were resistant to chloramphenicol, erythromycin and tetracycline.
catQ and mef(I) were associated in an IQ module that was indistinguishable in Sag236 and Sag403. In
mating assays, chloramphenicol and erythromycin resistance proved transferable, at low frequency, only from
Sag236. Transconjugants carried not only catQ and mef(I), but also erm(TR), suggesting a linkage of the three
resistance genes in a mobile element, which, though seemingly non-mobile, was also detected in Sag403. The
new element (designated ICESag236, 110 kb) results from recombination of two integrative and conjugative
elements (ICEs) originally described in different streptococcal species: S. agalactiae ICESagTR7, carrying erm(TR);
and Streptococcus pneumoniae ICESpn529IQ, carrying the prototype IQ module.
Conclusions: These findings strengthen the notion that widespread streptococcal ICEs may form mosaics that
enhance their diversity and spread, broaden their host range and carry new cargo genes
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
Diffusion and Characterization of Pseudomonas aeruginosa Aminoglycoside Resistance in an Italian Regional Cystic Fibrosis Centre
No full textAims: Extensively-drug-resistant Pseudomonas aeruginosa constitutes a serious threat to patients suffering from Cystic Fibrosis (CF). In these patients, P. aeruginosa lung infection is commonly treated with aminoglycosides, but treatments are largely unsuccessful due a variety of resistance mechanisms. Here we investigate the prevalence of resistance to gentamicin, amikacin and tobramycin and the main aminoglycoside resistance genes found in P. aeruginosa strains isolated at a regional CF centre.
Results: A total number of 147 randomly selected P. aeruginosa strains isolated from respiratory samples sent by the Marche regional Cystic Fibrosis Centre to the Microbiology lab, were included in this study. Of these, 78 (53%) were resistant to at least one of the three aminoglycosides tested and 27% were resistant to all three antibiotics, suggesting a major involvement of a chromosome-encoded mechanism, likely MexXY-OprM efflux pump overexpression. A specific pathogenic clone (found in 7/78 of the aminoglycoside resistant strains) carrying ant(2′′)-Ia was isolated over time from the same patient, suggesting a role for this additional resistance gene in the antibiotic unresponsiveness of CF patients.
Conclusions: The MexXY-OprM efflux pump is confirmed as the resistance determinant involved most frequently in P. aeruginosa aminoglycoside resistance of CF lung infections, followed by the ant(2′′)-Ia-encoded adenylyltransferase. The latter may prove to be a novel target for new antimicrobial combinations against P. aeruginosa
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
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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