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Antimicrobial spectrum activity of bacteriocinogenic Staphylococcus strains isolated from goat and sheep milk
No full textBacteriocins have attracted great attention as potential alternatives to antibiotics and chemical food additives. In the present study, 243 Staphylococcus isolates from milk samples (n = 110) of goat and sheep herds located in Fars province, Iran, were screened for antimicrobial substance production. Twenty-eight isolates showed an antagonistic activity against the indicator strain Micrococcus luteus ATCC 4698. The susceptibility of all antimicrobial substances to proteolytic enzymes allowed us to consider them as bacteriocin-like inhibitory substances (BLIS). The term BLIS is applied to uncharacterized proteinaceous antimicrobials produced by gram-positive bacteria. Based on molecular identification methods, the isolates belonged to the species Staphylococcus chromogenes, Staphylococcus epidermidis, Staphylococcus haemolyticus, Staphylococcus pseudintermedius, Staphylococcus aureus, and Staphylococcus agnetis. Pulsed-field gel electrophoresis revealed a high level of genotype diversity among the Staph. chromogenes isolates. All of the isolates harbored nukA or bsaA2 genes, suggesting that their BLIS were related to nukacin or Bsa. The antimicrobial compounds from test strains were not effective against gram-negative pathogens, including Salmonella enterica serovar Typhimurium, Escherichia coli O157:H7, and Klebsiella pneumonia as well as the indicator mold Aspergillus fumigatus. All the gram-positive targets, including Bacillus cereus, Listeria monocytogenes, Enterococcus faecalis Ef37 (a tyramine-producer strain), Lactobacillus saerimneri 30a (a histamine-producer strain), and methicillin-resistant Staph. epidermidis, were inhibited by the Staph. chromogenes isolates. Staphylococcus haemolyticus 4S12 was able to inhibit the majority of gram-positive bacteria. Listeria monocytogenes strains were the only indicators sensitive to the antimicrobial agents produced by Staph. agnetis 4S97B. The other Staphylococcus strains were ineffective on all the organisms tested. Based on their inhibitory capacities, the BLIS produced by the Staph. chromogenes isolates seem to be interesting candidates for developing novel antimicrobial agents
Safety hazards in bacteriocinogenic Staphylococcus strains isolated from goat and sheep milk
No full textIn this study, 28 bacteriocinogenic Staphylococcus strains isolated from goat and sheep milk were subjected to the PCR detection of enterotoxin genes (sea-see), enterotoxin-like toxin Q gene (selq), toxic shock syndrome toxin gene (tst1), and antibiotic resistance genes. They were also evaluated for phenotypic resistance against 10 antibiotics and hemolytic activity. The tyramine and histamine production was investigated using the agar plate assay and capillary zone electrophoretic analysis (CZE). Twenty-five isolates harbored at least one enterotoxin gene. The gene sec was the most frequent (89%). The gene tst1 was found in 84% of sec-positive isolates. The occurrence of antibiotic resistance genes was in the order of blaZ/tetK (100%), mecA/ermB (86%), ermC (50%), and tetM (18%). The genes ermA, aac(6')Ie-aph(2′′)Ia, vanA, and vanB were absent in all the isolates. Nineteen isolates were phenotypically susceptible to all the antibiotics. The only isolate with phenotypic resistance to penicillin G and oxacillin was S. epidermidis 4S93 which had a different SmaI-PFGE profile from those of the other S. epidermidis strains. All the S. haemolyticus and S. pseudintermedius isolates were not susceptible to trimethoprim. Twenty-five isolates showed complete or partial hemolytic activity. None of the isolates was able to decarboxylate tyrosine, while CZE analysis revealed histamine formation activity in S. haemolyticus 4S12. The occurrence of safety risks in the isolates reinforces the need for regular monitoring of food-producing animals to mitigate the risks of multidrug resistant and zoonotic pathogens. Moreover, none of the isolates fulfilled the safety criteria to be used as starter cultures or biopreservatives
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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