1,720,954 research outputs found
Efeito de carreador lipídico nanoestruturado contendo quitosana em células livres e biofilme de Escherichia coli
No full textUrinary tract infection (UTI) is the most common hospital acquired pathological process and indwelling urinary catheters increase the risk of bacteriuria, which can progress to a serious condition. This infection usually follows formation of biofilm on both the internal and external catheter surface. The uropathogenic bacteria Escherichia coli is the most common infecting microorganism on catheter and its biofilms have been studied as a platform to select strategies to control UTIs. The present study examined whether a nano delivery system containing chitosan affected the growth of uropathogenic biofilms of E. coli. This work was divided in two stages, the first involved comparing adhesion surfaces most used in in vitro biofilm models and the second evaluated the susceptibility of free cells and biofilm of E. coli to a nanostructured lipid carrier coated with chitosan (NLC-chitosan). Thus, E. coli biofilms were formed on catheter, glass slides or tissue culture plates for 5 days and the composition of biofilm was evaluated. In the second stage of the work, NLC-chitosan was prepared using the emulsion and sonication method, and further characterized with respect to particle size, polydispersity index, and zeta potential. After determining the minimum inhibitory (MIC) and bactericidal concentrations (MBC), E. coli biofilms were grown on catheter specimens. At the 48, 72, 96, and 120 hours of growth, biofilms were exposed to 0.9% NaCl solution (negative control), 0.12% chlorhexidine solution (positive control), or NLC-chitosan (final chitosan concentration of 0.28%). After 24 hours of treatment, the biofilms were collected to analyze their bacterial viability. Data were statistically analyzed by Tukey-Kramer or Tukey test with a level of significance of 5%. Bacterial colony viability was higher in catheter compared to glass slides or plates (p0.05) as well as glass slides and plate (p>0.05) for protein quantification. Regarding second work stage, NLC-chitosan preparation had bimodal particle size distribution with mean size of 292.9 ± 2.5 nm and polydispersity index of 0.24 ± 0.03, and positive zeta potential (+19.1 ± 0.2) indicating the nanoparticle coating by chitosan. Analysis of MIC and MBC values revealed that formulation inhibited bacterial growth and exerted bactericidal action at concentrations 100 times higher than those required for chlorhexidine digluconate (positive control). Compared with the control groups, NLC-chitosan affected bacterial colony viability of biofilms at all ages studied (p0,05) ou entre as lâminas de vidro e a placa (p> 0,05). Em relação à segunda etapa do trabalho, a preparação de CLN-quitosana apresentou distribuição bimodal de tamanho de partícula com tamanho médio de 292,9 ± 2,5 nm, índice de polidispersividade de 0,24 ± 0,03 e potencial zeta positivo (+19,1 ± 0,2), indicando o revestimento de nanopartículas pela quitosana. A análise dos valores de CIM e CBM revelou que a formulação inibiu o crescimento bacteriano e exerceu ação bactericida em concentrações 100 vezes maior do que a necessária para o digluconato de clorexidina (controle positivo). Comparado com os grupos controle, a CLN-quitosana afetou a viabilidade bacteriana dos biofilmes em todas as idades avaliadas (p<0,05). Sendo assim, os resultados sugerem que o cateter é a superfície adequada para estudar biofilmes de E. coli. Tanto as células livres quanto os biofilmes foram afetados pelo CLN-quitosana. No futuro, o cateter urinário pode ser utilizado como modelo para estudar ITUs com populações mistas de bactérias e o efeito de CLN-quitosana ou de sua associação com outros antimicrobianos poderá ser avaliado
BIOFILM: FORMATION AND NATURAL PRODUCTS’ APPROACH TO CONTROL – A REVIEW
Get PDFBiofilm formation, especially on indwelling medical devices such as catheters, can result in infections and substantially affect patients’ quality of life. Biofilm-associated infections have led to increased morbidity and mortality, increased cost of treatment, and length of hospital stay. However, all of the identified consequences of the biofilm-associated infections had been attributed to the reduced susceptibility of biofilm to conventional antimicrobial agents which has necessitated the development of a new strategy for biofilm infections control, thereby making a search for more effective antimicrobial agents from plant source inevitable. So far, some antimicrobial agents (crude or isolated compounds) from plant sources affect a specific stage of biofilm development while a few of them have been developed into a suitable dosage form for biofilm control. In this review, an attempt is made to look into some definitions of biofilm by “biofilmologists”, stages in biofilm formation, mechanisms of resistance in biofilm, biofilm control strategies, the use of some natural products in biofilm control and concepts of probiotics as agents of biofilm control
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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