1,720,980 research outputs found
Presenza di ceppi di Enterococcus faecium vancomicina-resistenti in formaggi italiani
No full textIn this research, samples of artisanal and industrial Italian cheeses were acquired from different supermarkets in Sicily from September 2000 to February 2001, and were analysed for vancomycin-resistant enterococci (VRE). The analyzed cheeses could be divided into three categories, based on the number of enterococci as determined on Kanamycin Aesculin Agar Base (KAA). An enrichment step in Tripticase Soy Yeast Extract Broth (TSYE) supplemented with 8 g/mL vancomycin and subsequently plating out onto KAA containing vancomycin allowed the individuation of vancomycin-resistant lactic acid bacteria in 46.7% of the cheese samples analyzed. These bacteria were assigned, on the bases of their morphology and metabolic characteristics, to the genera Leuconostoc, Pediococcus and Lactobacillus, known for their intrinsic vancomycin resistance. Strains of VRE were detected in only 3 out of 30 (10%) samples of different cheeses, i.e. Asiago cheese, Pecorino Pepato cheese and grated cheese, all included in the category of cheeses with a high number of enterococci. The VRE isolates, identified as Enterococcus faecium by multiplex PCR and Specific And Random Amplification (SARA)-PCR analysis, were highly resistant to vancomycin and teicoplanin (MIC > 64 μg/mL) and harboured the vanA gene, as shown by both PCR techniques. The genetic fingerprints obtained with a RAPD-PCR assay revealed that the isolates were genotipically heterogenous thus suggesting that different VRE strains are able to colonise different Italian cheeses. Also the results obtained in this study indicate that the presence of bacteria with acquired antibiotic resistance should be closely monitored and controlled in order to make food safer
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
Probiotic features of Lactobacillus strains isolated from Ragusano and Pecorino Siciliano cheeses
No full textIn the present study 177 Lactobacillus spp. strains, isolated from Ragusano and Pecorino Siciliano cheeses, were in vitro screened for probiotic traits, and their characteristics were compared to those of Lactobacillus rhamnosus GG, commercial strain. Based on acidic and bile salt resistance, thirteen Lactobacillus strains were selected. The multiplex-PCR application revealed that nine strains belonged to L. rhamnosus species and four to Lactobacillus paracasei species. All selected strains were further investigated for transit tolerance in simulated upper gastrointestinal tract (GI), for adhesion capacity to human intestinal cell lines, for hydrophobicity, for co-aggregation and auto-aggregation and for antimicrobial activities. Moreover, antibiotic resistance, hemolytic and bile salt hydrolase activities were investigated for safety assessment.Viable counts after simulated gastric and duodenal transit revealed that overall the selected lactobacilli tolerated better pancreatic juice and bile salts than acidic juice. In particular, three L. rhamnosus strains (FS10, FS2, and PS11) and one L. paracasei strain (PM8) increased their cell density after the simulated GI transit. The same strains showed also high percentage of auto-aggregation and co-aggregation with Escherichia coli. All strains were effective against both Staphylococcus aureus and E. coli and variability was achieved versus Listeria monocytogenes and Enterococcus faecalis used as pathogenic indicator strains.Different behavior was revealed by strains for adhesion ability and hydrophobicity, which are not always linked each other and are strongly strain-dependent. From the safety point of view, no isolate showed hemolytic and bile salt hydrolase activities, except one, and most of the strains were sensitive to a broad range of clinical antibiotics.This work showed that the L. rhamnosus FS10 and the L. paracasei PM8 are good promising probiotic candidates for further in vivo investigations
Bile salt hydrolase: The complexity behind its mechanism in relation to lowering-cholesterol lactobacilli probiotics
Full text linkBile Salt Hydrolase (BSH) is a bacterial enzyme (EC 3.5.1.24) that initiates the crucial deconjugation of bile acids (BAs), a process necessary for their transformation into secondary BAs by gut microbes. Recent advance has delved deeper into BAs, recognizing them as endocrine molecules capable of modulating lipid and sugar metabolism in the host. In this review, we elucidate how this wealth of research has broadened our understanding about the intricate mechanisms between BAs and the gut microbiota beyond BSH, underlying the hypocholesterolemic effects of probiotic lactobacilli. We highlight the expanded range of various species of lactobacilli with proven cholesterol-lowering activity both in vitro and in vivo associated with BSH activity. In addition, a summary of genomic and metagenomic studies investigating bsh genes in both gut microbiota and lactobacilli is provided, to be used as an additional tool for the selection of a potential lactobacilli probiotic
Insights on the bacterial composition of Parmigiano Reggiano Natural Whey Starter by a culture-dependent and 16S rRNA metabarcoding portrait
Full text link: Natural whey starters (NWS) are undefined bacterial communities produced daily from whey of the previous cheese-making round, by application of high temperature. As a result, in any dairy plant, NWS are continuously evolving, undefined mixtures of several strains and/or species of lactic acid bacteria, whose composition and performance strongly depend on the selective pressure acting during incubation. While NWS is critical to assure consistency to cheese-making process, little is known about the composition, functional features, and plant-to-plant fluctuations. Here, we integrated 16S rRNA metabarcoding and culture-dependent methods to profile bacterial communities of 10 NWS sampled in the production area of Parmigiano Reggiano cheese. 16S rRNA metabarcoding analysis revealed two main NWS community types, namely NWS type-H and NWS type-D. Lactobacillus helveticus was more abundant in NWS type-H, whilst Lactobacillus delbrueckii/St. thermophilus in NWS type-D, respectively. Based on the prediction of metagenome functions, NWS type-H samples were enriched in functional pathways related to galactose catabolism and purine metabolism, while NWS type-D in pathways related to aromatic and branched chain amino acid biosynthesis, which are flavor compound precursors. Culture-dependent approaches revealed low cultivability of individual colonies as axenic cultures and high genetic diversity in the pool of cultivable survivors. Co-culturing experiments showed that fermentative performance decreases by reducing the bacterial complexity of inoculum, suggesting that biotic interactions and cross-feeding relationships could take place in NWS communities, assuring phenotypic robustness. Even though our data cannot directly predict these ecological interactions, this study provides the basis for experiments targeted at understanding how selective regime affects composition, bacterial interaction, and fermentative performance in NWS
FoodOmics as a new frontier to reveal microbial community and metabolic processes occurring on table olives fermentation
Full text linkTable olives are considered the most widespread fermented food in the Mediterranean area and their consumption is expanding all over the world. This fermented vegetable can be considered as a natural functional food thanks to their high nutritional value and high content of bioactive compounds that contribute to the health and well-being of consumers. The presence of bioactive compounds is strongly influenced by a complex microbial consortium, traditionally exploited through culture-dependent approaches. Recently, the rapid spread of omics technologies has represented an important challenge to better understand the function, the adaptation and the exploitation of microbial diversity in different complex ecosystems, such as table olives. This review provides an overview of the potentiality of omics technologies to in depth investigate the microbial composition and the metabolic processes that drive the table olives fermentation, affecting both sensorial profile and safety properties of the final product. Finally, the review points out the role of omics approaches to raise at higher sophisticated level the investigations on microbial, gene, protein, and metabolite, with huge potential for the integration of table olives composition with functional assessments
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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