1,720,961 research outputs found
Exopolysaccharides produced by Inquilinus limosus, a new pathogen of cystic fibrosis patients: novel structures with usual components
No full textInteraction of antimicrobial peptides with bacterial polysaccharides from lung pathogens
No full textThe interaction of two cathelicidin antimicrobial peptides, LL-37 and SMAP-29, with three bacterial polysaccharides, respectively, produced
by Pseudomonas aeruginosa, Burkholderia cepacia and Klebsiella pneumoniae, was investigated to identify possible mechanisms adopted
by lung pathogens to escape the action of innate immunity effectors. In vitro assays indicated that the antibacterial activity of both peptides
was inhibited to a variable extent by the three polysaccharides. Circular dichroism experiments showed that these induced an -helical
conformation in the two peptides, with the polysaccharides from K. pneumoniae and B. cepacia showing, respectively, the highest and the
lowest effect. Fluorescence measurements also indicated the presence of peptide–polysaccharide interactions. A model is proposed in which
the binding of peptides to the polysaccharide molecules induces, at low polysaccharide to peptide ratios, a higher order of aggregation, due to
peptide–peptide interactions. Overall, these results suggest that binding of the peptides by the polysaccharides produced by lung pathogens
can contribute to the impairment of peptide-based innate defenses of airway surface
Exopolysaccharides produced by clinical strains belonging to the Burkholderia cepacia complex
No full textBackground: In the frame of a research line dedicated to better clarify the role of exopolysaccharides (EPS) in bacterial virulence, EPS produced by species of the Burkholderia cepacia complex (Bcc), namely Burkholderia multivorans, Burkholderia cenocepacia, and a Bcc member of undetermined genomovar, all isolated at the Cystic Fibrosis Regional Centre of Florence (Italy), were investigated for they structural properties.
Methods: Three strains of B. multivorans, three of B. cenocepacia and one of a Bcc member of undetermined genomovar were isolated from CF patients. The reference strains C1576 and J2315, for genomovar II and III, respectively, were included in the study. The bacteria were
grown on solid media, the exopolysaccharides produced were purified, and their structures were determined. In addition, sugar analysis of sputum samples was accomplished to search for EPS produced in vivo.
Results: Six strains out of seven produced the exopolysaccharide cepacian, while one strain of B. multivorans produced a completely different polymer, previously known in the literature as PS1. Two strains synthesised very small amounts of EPS. No definitive evidence for the presence of cepacian in sputum samples was found.
Conclusions: Most strains examined produced abundant amounts of polysaccharides. Cepacian was the most common EPS isolated and its production was not associated to a particular genomovar
First report of a lyase for cepacian, the polysaccharide produced by Burkholderia cepacia complex bacteria
No full textActivity of antimicrobial peptides in the presence of polysaccharides produced by pulmonary pathogens.
No full textAntimicrobial peptides (AMPs) are secreted in the airway and contribute to initial defence against inhaled pathogens. Infections
of the respiratory tract are a major cause of morbidity and mortality in preterm newborns and in patients with cystic fibrosis
(CF). In this latter group, the state of chronic lung infection is due to the ability of bacteria to grow as mucoid biofilm, a
condition characterised by overproduction and release of polysaccharides (PSs). In this study, we investigate the effect of PSs
produced by lung pathogens such as Pseudomonas aeruginosa, Klebsiella pneumoniae andmembers of the Burkholderia cepacia
complex on the antibacterial activity of structurally different peptides. The AMPs tested in this study include the cathelicidin
LL-37 and the β-defensin hBD-3 from humans, both released at the alveolar level, as well as peptides from other mammals, i.e.
SMAP-29, PG-1 and Bac7(1-35). Susceptibility assays, time killing and membrane permeabilization kinetics experiments were
carried out to establish whether PSs produced by lung pathogens may be involved in the poor defence reaction of infected
lungs and thus explain infection persistence. All the PSs investigated inhibited, albeit to a different extent, the antibacterial
activity of the peptides tested, suggesting that their presence in the lungs of patients with CF may contribute to the decreased
defence response of this district upon infection by PS-producing microorganisms. The results also show that inhibition of the
antibacterial activity is not simply due to ionic interaction between the negatively charged PSs and the cationic AMPs, but it
also involves other structural features of both interactors
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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