1,721,738 research outputs found
La multiresistenza in Salmonella: caratterizzazione molecolare di un nuovo clone emergente di Salmonella enterica sierotipo Typhimurium
No full textSalmonella enterica sierotipo Typhimurium (STM) rappresenta la prevalente causa di gastroenterite trasmessa da alimenti in Italia, con la maggior parte degli isolati con resistenza multipla agli antibiotici, principalmente ad ampicillina (A), cloramfenicolo (C), streptomicina (S), sulfamidici (Su) e tetraciclina (T) (ACSSuT).
Un nuovo pattern di resistenza (R-type) ASSuT, mancante della resistenza a C, è recentemente emerso in Italia tra ceppi di STM e della sua variante monofasica, Salmonella enterica subspecie enterica sierotipo S. 4,[5],12:i:– .
L’obiettivo principale di questa tesi è stato la caratterizzazione di ceppi di STM e di S. 4,[5],12:i:– con R-type ASSuT, usando tecniche di tipizzazione molecolari e fenotipiche, quali l’elettroforesi in campo pulsato (PFGE) e la fagotipizzazione, allo scopo di valutare la loro origine clonale e la loro relazione con i ceppi ACSSuT. Usando il database Pulse-Net Europe è stata valutata la presenza di ceppi ASSuT in altre nazioni Europee al fine di allestire una collezione internazionale di ceppi. Questa collezione è stata ulteriormente caratterizzata, identificando i geni di resistenza, investigando la loro localizzazione, e determinando la regione di resistenza.
Sia tra ceppi di STM che di S. 4,[5],12:i:–, il principale profilo di PFGE è rappresentato da STYMXB.0079, mentre i ceppi STM ACSSuT appartengono ai profili STYMXB.0061 e STYMXB.0067. L’analisi dei profili di PFGE con il software Bionumerics ha mostrato che più del 90% dei ceppi ASSuT e ACSSuT appartenevano a due distinti clusters con un’omologia genetica del 73%, dati che dimostrano l’appartenenza dei ceppi ASSuT ad un'unica linea clonale differente da quella dei ceppi ACSSuT.
La maggior parte dei ceppi con profilo ASSuT non erano tipizzabili (DTNT) attraverso la fagotipizzazione o appartenevano al fagotipo U302. Al contrario i ceppi ACSSuT appartenevano principalmente al fagotipo DT104.
Successivamente, nel database Pulse-Net Europe, è stato possibile identificare ceppi ASSuT, sia STM che S. 4,[5],12:i:– isolati in Danimarca ed Inghilterra, con profili di PFGE identici o strettamente correlati a quelli dei ceppi italiani, dati che indicano che il clone ASSuT è presente anche in altri paesi Europei.
Al fine di identificare i geni responsabili della resistenza sono stati selezionati 64 ceppi di STM e S. 4,[5],12:i:– ASSuT, e 11 ceppi di STM con differenti R-type e profili di PFGE, usati come controlli. Tutti i ceppi provenivano da infezioni umane ed erano stati isolati in Italia, Danimarca e Inghilterra.
Tutti i ceppi ASSuT erano positivi per i seguenti geni di resistenza: blaTEM, strA-strB, sul2 and tet(B). Successivi esperimenti di localizzazione hanno dimostrato che i geni di resistenza ASSuT sono localizzati sul cromosoma
Infine, è stata determinata la sequenza completa del cluster di resistenza ASSuT. Questo cluster è composto da due isole di resistenza (RI1 e RI2) separate da DNA cromosomale. In particolare, RI1 è compresa tra due IS26 e contiene deltatnp3R, blaTEM-1, tnpB, seguito da strB, strA, sul2, repC, deltarepA ed un’atra IS26. RI2 è anch’essa compresa tra due IS26, comprendenti deltaIS10L, il gene di resistenza alla tetraciclina, IS1, l’operone per la resistenza al mercurio, il gene yaeA, e un’ ipotetica transposasi (tniAdelta). Entrambe le RIs mostrano il 99% di identità con due regioni adiacenti del plasmide pHCM1, presente nel ceppo di S. Typhi isolato in Vietnam. Le sequenze di inserzione IS26 potrebbero aver avuto un ruolo nella formazione di questo cluster di resistenza, ma quest’ipotesi deve essere ancora verificata.
In conclusione il lavoro di questa tesi indica che i ceppi ASSuT di STM e S. 4,[5],12:i:–, in aumento in Italia, appartengono ad un'unica linea clonale e che i ceppi S. 4,[5],12:i:– circolanti nella nostra nazione, derivano principalmente da questa linea clonale di STM. Inoltre il clone ASSuT è diffuso anche in Danimarca ed Inghilterra. Il pattern di antibiotico resistenza conferito da un’isola di resistenza cromosomale, con un’organizzazione simile ad altri cluster precedentemente descritti, suscita preoccupazione poichè la resistenza può essere mantenuta stabilmente in assenza di pressione selettiva.Salmonella enterica serovar Typhimurium (STM) represents the prevalent cause of foodborne gastroenteritis in Italy with the majority of isolates exhibiting multidrug resistance, mainly to ampicillin (A), chloramphenicol (C), streptomycin (S), sulfonamide (Su) and tetracycline (T) (ACSSuT).
However, a new resistance pattern (R-type) ASSuT, lacking resistance to C, has recently emerged in Italy among strains of STM and of its monophasic variant, Salmonella enterica subspecie enterica serovar S. 4,[5],12:i:– .
The main objective of this thesis has been the characterization of STM and S. 4,[5],12:i:– strains with R-type ASSuT, using both molecular and phenotypic typing technique, pulsed-field gel electrophoresis (PFGE) and phage typing, in order to evaluate their clonal origin and the relationships with the ACSSuT strains. In addition, by the use of the Pulse-Net database it was evaluated if ASSuT strains were present in other European countries in order to set up an international collection of these strains. This collection has been further characterized with the identification of resistance genes, the investigation of their localization, and determination of the resistance region.
Among both the STM and S. 4,[5],12:i:– ASSuT strains, the predominant PFGE profile was STYMXB.0079, while the STM ACSSuT strains belonged to the STYMXB.0061 and STYMXB. 0067. Bionumerics cluster analysis of PFGE profiles showed that more than 90% of ASSuT and ACSSuT resistant strains were included in two distinct clusters with a genetic homology of 73% each other, suggesting that the ASSuT resistant strains belong to a same clonal lineage different from that of the ACSSuT strains.
Phage typing showed that both STM and S. 4,[5],12:i:– ASSuT strains were not typeable (DTNT) or U302. A different figure was observed for the ACSSuT strains: the STM strains mostly belonged to DT104.
The Pulse-Net Europe database, allowed us to identify ASSuT strains, both STM and S. enterica 4,[5],12:i:–, isolated in Denmark and UK, with the same or very closely related PFGE patterns as the Italian strains, suggesting that the ASSuT clone is circulating in different European countries.
The resistance genes were identified in 64 strains of STM and S. enterica 4,[5],12:i:–with ASSuT R-type and in 11 STM strains with different resistance patterns and PFGE profiles as controls. All strains were isolated from human infections in Italy, Denmark and UK.
All the ASSuT strains were positive for the following resistance genes: blaTEM, strA-strB, sul2 and tet(B). The control strains showed the same gene pattern, in accordance with their resistance profiles. A variability of the genes conferring resistance to tetracycline was detected. Localization experiments demonstrated that the ASSuT resistance genes are chromosomally located.
Finally, the complete sequence of ASSuT resistance cluster was determined. This cluster is composed by two resistance island (RI1 and RI2) divided by chromosomal DNA. In particular, RI1 is comprised between two IS26 and contains deltatnp3R, blaTEM-1, tnpB , followed by strB, strA, sul2, repC, DeltarepA and another IS26. RI2 is bracketed by two IS26, comprising deltaIS10L, tetracycline resistance gene, IS1, the operon for resistance to mercury, yaeA gene, and a putative transposase (tniAdelta). Both this RIs show 99% sequence identity to two adiacent region of pHCM1 plasmid, harbored in S. Typhi isolated in Vietnam. IS26 elements could have played a role in the assembly of this resistance cluster but it will be investigated more in detail.
In conclusion the work of this thesis indicates that the tetra-resistant ASSuT strains of STM and S. 4,[5],12:i:–, increasingly isolated in Italy, belong to a same clonal lineage and that the S. 4,[5],12:i:– strains circulating in our country, mainly derive from this STM clonal lineage. ASSuT clone is also circulating in Denmark and United Kingdom. The antimicrobial resistance pattern conferred by a chromosomal island, with an organization similar to previously reported clusters, deserves concern since the resistance could be stably maintained even in the absence of selective pressure
Neuroscience and risk tolerance in financial decision-making processes
No full textPer le scienze della mente le nostre decisioni scaturiscono dall’interazione continua tra processi razionali e processi emotivi. Questo articolo presenta le anticipazioni di una ricerca che approfondisce alcuni aspetti della componente emotiva che interviene nell’assunzione del rischio in finanza. Dalla collaborazione interdisciplinare tra studiosi di neuroscienze e di discipline finanziarie è derivata una serie di esperimenti svolti su un campione vasto e stratificato di individui, con competenze differenti: clienti e dipendenti di banche, promotori finanziari, trader ed asset manager. In essi si mettono a confronto la validità di misurazioni di tolleranza al rischio classiche (questionari) e di tecniche meno consuete per il mondo della finanza (test psicofisiologici).
The sciences of mind recognize that our decisions arise from the interaction between rational and emotional processes.This article explores some aspects of the emotional components acting in financial risk decision making process.The research has been conducted on a large stratified sample of individuals and professionals and has compared the classical systems for measuring risk tolerance and most innovative techniques applied by neuroscience
Unsustainable debt: impulsiveness, financial literacy and economic factors
No full textUsing in-person survey data, we investigate the relationship between the sustainability of household indebtedness and some individual psychological traits. We make use of validated tools in neuroeconomic research to jointly analyse different facets of household psychology, such as impulsiveness, future orientation and attitude toward uncertainty and their effect upon a condition of unsustainable debt. We also condition our model to socio-demographic and economic characteristics of households, as well as on the level of financial literacy and the occurrence of a recent economic distress.
The empirical analysis highlights that psychological traits of households have impacts not only on use but also on mis-use of credit. There are three main evidences that need to be pointed out. Firstly, we find that a condition of unsustainable debt occurs more often among individuals who are impulsive, less inclined to plan for the future and less concerned about unexpected events. Secondly, these psychological traits display an effect that is over and beyond the recent occurrence of an economic shock. Finally, financial illiterate individuals are more likely to incur in unsustainable debts, even though the positive effect of financial literacy is not able to completely overcome the detrimental effects of some psychological biases. These results are of particular interest for policy makers in order to define policy measures aimed at providing competencies and tools that can help individuals to manage their resources appropriately and to take sustainable borrowing decisions
Insights into the Reactivity of Thiophene: Heterogeneous Alkylation
No full textThe importance of thiophene derivatives in the fine chemical industry lies in the use of this class of molecules as raw materials in the synthesis of drugs, fragrances and pesticides. Nowadays, the synthesis of these molecules is multistep and expensive. The gas phase alkylation of thiophene on solid acid catalysts has been deeply studied by focusing on the possibility to control the product distribution of the reaction, paying particular attention to the relative amount of the 2- and 3-alkylthiophene, kinetic and thermodynamic products respectively. The difficulties in changing the 2:3 isomer ratio have been justified through the comprehension of thiophene behavior on the catalyst surface, that is responsible for the complex adsorption/desorption phenomena. It has been showed that the reaction is mainly affected by the strong adsorption of thiophene on the catalytic sites, with the critical step of the reaction represented by the saturation of the catalyst surface
Heterogeneity in entrepreneurial intent: the role of gender across countries
No full textPurpose – This paper aims to improve knowledge of individual heterogeneity in affecting the
entrepreneurial attitude, taking socioeconomic drivers under control thanks to a cross-country analysis.
The authors operate a “selection” of proxy for individual heterogeneity, mainly based on gender,
demographical features, personal attitude and intrinsic motivation.
Design/methodology/approach – This exploration is supported by an empirical analysis based on
the Global Entrepreneurship Monitor (GEM), for the period 2001-2012, and for a selection of 37
countries. It is expected that gender and further individual variables have an impact on the probability
to become a nascent entrepreneur (e.g. age, level of education, self-confidence, social perception of
self-employment as career choice). This paper evaluates the degree of consistency of these variables
across very dissimilar countries.
Findings – Gender and confidence on own skill play a significant and consistent effect on the
entrepreneurial attitude, so these personal features are, per se, the driving-strength of entrepreneurial
intent. Conversely, fear of failure and belief on the status are not always statistically significant, or not
homogenous in their relationship: socioeconomic or country-specific characteristics are strong and sort
out in an unpredictable relationship between these variables and the willingness to run new ventures.
Research limitations/implications – A limited selection of individual features constrained by
availability of information from the GEM data set.
Practical implications – The motivation of this paper is to focus-back attention on intra-individual
features that may affect entrepreneurship and to support evidence of whether individual heterogeneity
is able to affect the entrepreneurial attitude, taking socioeconomic drivers under control.
Social implications – An institutional and political commitment should be intensified to reduce the
waste of opportunities that is associated with any forms of self-exclusion from entrepreneurship, such
as those based on gender (being women) or (low) self-esteem.
Originality/value – Due to the “individual” perspective, this paper adds to previous studies that
exploited the GEM data set because they mostly follow an institutional conceptual framework
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
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