1,720,961 research outputs found
Characterisation of biofilm-forming Staphylococcus epidermidis clinical isolates
No full textObjective: Staphylococcus epidermidis is one of the bacterial species mainly implicated in foreign body associated infections. We have characterized several S.epidermidis clinical isolates for their ability to form biofilms and their resistance to antibiotics.
Methods: 76 S.epidermidis strains isolated from implantable medical devices have been collected from hospitals of Central Italy. Susceptibility to penicillin, methicillin, erythromycin and tetracycline has been determined in vitro by E-test according to NCCLS guidelines. The specific antibiotic resistance determinants have been checked by PCR (blaZ, mecA, ermA, ermB, ermC, msrA, tetK and tetM). The ability to form biofilms has been determined: (i) by PCR, detecting genes specific for attachment and biofilm development (icaADBC operon, aap, and atlE); (ii) by Congo Red Agar (CRA) plate test to assay the production of polisaccaridic intercellular adhesin (PIA); (iii) by crystal violet (CV) stain to determine the biofilm biomass development on polystyrene microtiter plates; (iv) and by CSLM microscopy observations to investigate biofilm structure.
Results: 94% of the strains under study was resistant to penicillin, 87% to methicillin, 72% to erythromycin and 25% to tetracycline. On the side of biofilm-specific genes detection, 66% of strains was positive to ica operon genes, 82% possessed atlE gene, and 42% aap determinant. In 89% of the population, the CRA test confirmed the correlation between the presence of ica genes and slime expression. The CV assay classified the quasitotality of our strains (97%) as biofilm producers on plastic surface. In addition, the distribution of optical density values (OD540) obtained after CV stain, showed a significant statistical difference in biofilm biomass development between the ica- ADBC-positive strains and the icaADBC-negative ones. Finally, a correlation, although not always present, has been observed between ability of the strains to develop in a high-structureted biofilm and specific biofilm-formation determinants.
Conclusions: The investigated bacterial population shows a very high and alarming level of resistance to all tested drugs. Although the specific determinants for biofilms formation are not always present, nevertheless all the strains are able to develop in sessile form showing that different and not still identified factors could work together in the formation and organization of staphylococcal complex microbial communities
Permethrin and its metabolites affects Cu/Zn Superoxide conformation: fluorescence and in silico evidences
No full textThe proclivity of permethrin and its metabolites to affect the structure and activity of Cu/Zn Superoxide dismutase (SOD) has been investigated by using intrinsic fluorescence and 8-ANS fluorescence techniques. In silico Molecular docking investigations were carried out in order to assess the way of interaction at molecular level between SOD and the considered ligands. Results show that both, permethrin and its metabolites are able to induce conformational variation on SOD. Permethrin and 3-phenoxybenzyl alcohol metabolite induce a blue shift toward the hydrophobic aminoacids Leu-101, Ile-102, Leu-104, Ile-110 and Ile-111, with a significant peak increase. An opposite effect was shown by 3-phenoxy benzaldehyde and 3-phenoxybenzoic acid with a progressive reduction of tyrosine fluorescence emission, without any shift. Computational findings confirm that all the molecules considered have more than one allosteric binding site but none of them interact with SOD at its catalytic Cu/Zn cleft. Moreover, all the found binding poses are very close in binding energy thus demonstrating that there is not only a preferred interaction site but most of them are important due to their relative energy in equilibrium with a population strictly connected to the ligand concentration. In the obtained complexes, all the ligands are involved in many hydrogen bonds through their polar oxygen moieties but due to the presence of a common aromatic hydrophobic core, many hydrophobic interaction are due to the SOD nature rich in apolar aminoacids. Furthermore, for each ligand it can be pointed out the presence of a high populated docked structure with a specific interaction of permethrin and its metabolites with Tyr108, responsible of changes in fluorescence emission
Conformational changes induced by permethrin and its metabolites on Cu-Zn superoxide dismutase: fluorescence, computational and docking results
No full textThe aim of the present study is to investigate the proclivity of permethrin and its metabolites to affect the structure and activity of Cu/Zn superoxide dismutase (SOD) by using intrinsic fluorescence and 8-ANS fluorescence techniques. Computational results and docking were used in order to assess the way of interaction at molecular level between SOD and permethrin or its metabolites.
Results show that both, permethrin and its metabolites are able to induce conformational variation on SOD. Permethrin and 3-phenoxybenzyl alcohol metabolite induce a blue shift toward the hydrophobic aminoacids Leu-101, Ile-102, Leu-104, Ile-110 and Ile-111, with a significant peak increase. An opposite effect was shown by 3-phenoxy benzaldehyde and 3-phenoxybenzoic acid with a progressive reduction of tyrosine fluorescence emission, without any shift.
Computational results confirm that all the molecules considered have more than one allosteric binding site but none of them interact with SOD at the catalytic Cu,Zn cleft. Moreover, all this binding poses are very close in binding energy demonstrating that there is not only a preferred interaction site but that most of them are pharmacophoric important and due to their relative energy in equilibrium with a population strictly connected the ligand concentration.
All the ligands are involved in many hydrogen bonds through their polar oxygen moieties but due to the presence of a common aromatic hydrophobic core, many hydrophobic interaction are due to the SOD nature rich in apolar aminoacids. Computational results confirmed the specific interaction of permethrin and its metabolites with Tyr108, responsible of changes in fluorescence emission
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
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