1,720,962 research outputs found
Species distribution, clonal spread and AR gene transferability of enterococci recovered from raw meat and farm animals.
No full textMultidrug-resistant enterococci in animal meat and faeces and co-transfer from an Enterococcus durans to a human Enterococcus faecium
No full textAntibiotic pressure can induce the viable but nonculturable state in Staphylococcus aureus growing in biofilms
No full textObjectives: Staphylococcal biofilms are among the main causes of chronic implant-associated infections. We
have recently suggested that their transformation into viable but non-culturable (VBNC) forms (i.e. forms
capable of resuscitation) could be responsible for the recurrent symptoms. This work aims to establish
whether Staphylococcus aureus biofilms can give rise to VBNC forms capable of being resuscitated in suitable
environmental conditions, the role of different stressors in inducing the VBNC state and the conditions favouring
resuscitation.
Methods: S. aureus 10850 biofilms were exposed to different concentrations of antibiotic (vancomycin or quinupristin/
dalfopristin) and/or to nutrient depletion until loss of culturability. The presence of viable cells and their
number were examined by epifluorescence microscopy and flow cytometry. Gene expression was measured by
real-time PCR. Resuscitation ability was tested by growth in rich medium containing antioxidant factors.
Results: Viable subpopulations were detected in all non-culturable biofilms. However, viable cell numbers and
gene expression remained constant for 150 days from loss of culturability in cells from antibiotic-exposed biofilms,
but not in those that had only been starved. Resuscitation was obtained in rich medium supplemented
with 0.3% sodium pyruvate or with 50% filtrate of a late-log culture.
Conclusions: Our findings demonstrate that S. aureus can enter the VBNC state in infectious biofilms. The presence
of vancomycin or quinupristin/dalfopristin can inadvertently induce a true VBNC state or its persistence
in S. aureus cells embedded in biofilms, supporting previous findings on the role of staphylococcal biofilms in
recurrent infection
Valutazione della presenza di forme batteriche vitali ma non coltivabili (VBNC) di stafilococco presenti in biofilm associati a cateteri venosi centrali (CVC).
No full text
Direct detection of antibiotic resistance genes in specimens of chicken and pork meat
No full textAntibiotic resistance (AR) in bacteria, a major threat to human health, has emerged in the last few decades as a consequence of the selective
pressure exerted by the widespread use of antibiotics in medicine, agriculture and veterinary practice and as growth promoters in animal
husbandry.
The frequency of 11 genes [tet(M), tet(O), tet(K), erm(A), erm(B), erm(C), vanA, vanB, aac (6′)-Ie aph (2′′)-Ia, mecA, blaZ] encoding
resistance to some antibiotics widely used in clinical practice was analysed in raw pork and chicken meat and in fermented sausages as well as in
faecal samples from the relevant farm animals using a molecular approach based on PCR amplification of bacterial DNA directly extracted from
specimens.
Some of the 11 AR genes were highly prevalent, the largest number being detected in chicken meat and pig faeces. The genes found most
frequently in meat were tet(K) and erm(B); vanB and mecA were the least represented. All 11 determinants were detected in faecal samples except
mecA, which was found only in chicken faeces. erm(B) and erm(C) were detected in all faecal samples. The frequency of AR genes was not
appreciably different in meat compared to faecal specimens of the relevant animal except for vanB, which was more prevalent in faeces.
Our findings suggest that AR genes are highly prevalent in food-associated bacteria and that AR contamination is likely related to breeding
rather than processing techniques.
Finally, the cultivation-independent molecular method used in this work to determine the prevalence of AR genes in foods proved to be a rapid
and reliable alternative to traditional tools
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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