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SMGI in tourism planning: the role of customers’ preferences in spatial decision support.
Get PDFThe dissertation deals with the role of social media platform is playing as an information resource in
tourism both for customers (i.e. the tourists), who gather trustworthy information supporting the choice of
destinations and services from peers, and for businesses, which can use the same information for
improving their marketing strategies. The use of social media data can also offer new opportunities for
decision‐support in tourism planning. With improved understanding of the motivations of tourists and
tailoring tourism service supply, decision making can be facilitated by emphasizing the strengths of tourist
destinations for past and potential visitors.
However, this kind of information about tourists’ perceptions and opinions is not always properly analysed
by planners. Understanding the user satisfaction, which depends on factors related to both the location and
the services that the local industry proposes, may offer valuable information in tourism planning at regional
and local level. In the light of the above premises, the goal of this study is to propose an integrated
approach to investigate the relationships between tourists’ satisfaction, destination resources and tourism
industry for supporting design and decision‐making in regional tourism planning.
The methodology implemented in the thesis includes data collection from Booking and TripAdvisor.com
and their integration with authoritative territorial data. Spatial and statistical analysis techniques are
applied in order to assess tourists’ perceptions on success factors, which may be used as planning support
tools. Four cases study demonstrates the value of social media‐related data integrated by authoritative
information in tourism planning.
Finally, the dissertation proposes a critical discussion on the effectiveness of using the implemented
integrated approach in order to address other planning issues. The discussion underlines the potential of
the proposed approach in order to address other planning questions as well
Meccanismo d'azione del Pramipexolo nella terapia della malattia di Parkinson
Get PDFPramipexole (PPX) is a dopamine (DA) D3 and D2 receptors agonist widely used alone or in combination with levodopa as Dopamine Replacement Therapy in Parkinson’s disease. In clinical and preclinical studies, PPX improved motor deficits, this evidence led to lowering daily dose of levodopa, delaying the motor side effects associated with its use. Recently, PPX administration has been associated to the development of addictive-like behaviors related to the DA Dysregulation Syndrome, particularly in a subpopulation of treated patients, characterized by impulsive-compulsive personality traits as well as previous addiction’s experience.
Based on these evidences, the aim of this study was twofold: first to investigate the pharmacological action of PPX, using a unilateral model of Parkinson’s disease in which 6-OHDA was injected in the medial forebrain bundle. After two weeks, we tested in primed and naive rats, the ability of three different doses of PPX (0,035; 0,1 and 0,35 mg/kg s.c.), to induce contralateral turning behavior as well c-fos expression after pretreatment of DA D1 antagonist SCH 39166. Next, we checked the ability of PPX to induce contralateral rotations after D2 (eticlopride) and D3 (S33084) DA antagonist pretreatment. In order to investigate the role of PPX (0,05 mg/kg s.c.) in behavioral sensitization, we tested its effect with S33084 pretreatment in levodopa sensitized rats.
Second, we assessed the correlation between PPX treatment, Parkinson’s disease and the onset of DA Dysregulation Syndrome on Conditioned Place Preference (CPP) paradigm. To do this, 6-OHDA was injected bilaterally in DA striatal terminals, in three different strains of rat: the addiction prone Lewis (LEW), the addiction resistant Fisher 344 (F344) inbred strains, and the Sprague Dawley (SD) outbred strain. Furthermore, to test its rewarding properties, PPX was directly infused in the nucleus accumbens shell (NAc), a DA mesolimbic region known to be involved in the rewarding effects of drugs of abuse, in healthy rats belonging to the above mentioned strains.
We discovered that in primed rats, PPX (0,35 mg/kg s.c.) induced turning behavior that was increased by SCH 39166 pretreatment (0,1 mg/kg s.c.). No effect was seen in naive rats both for turning behavior and c-fos expression. D2 receptors antagonist eticlopride (0,1 mg/kg s.c.) reduced PPX-induced turning behavior more than D3 receptors antagonist S33084 (0,5 mg/kg s.c.), also a previous levodopa sensitization increased PPX-induced turning behavior on its first administration. This suggests that PPX’s action could be related to D2 stimulation, and it seems to require a previous D1/D2 stimulation to observe a behavioral outcome.
PPX (1 mg/kg s.c.) was able to induce a significant CPP in SD and LEW lesioned rats but not in F344 and control rats, and the persistence of preference was stronger in LEW than in SD rats. When injected into the NAc shell, PPX (5 μg/0.5 μl) induced CPP in all rat strains, but the persistence of its effect was more strong in LEW compared to SD and F344 rats. These results suggest that the parkinsonian state might be more sensitive to the rewarding properties of PPX, which do not seem entirely influenced by phenotype
Cloud-based solutions supporting data and knowledge integration in bioinformatics
Get PDFIn recent years, computer advances have changed the way the science progresses and have
boosted studies in silico; as a result, the concept of “scientific research” in bioinformatics
has quickly changed shifting from the idea of a local laboratory activity towards Web
applications and databases provided over the network as services. Thus, biologists have
become among the largest beneficiaries of the information technologies, reaching and
surpassing the traditional ICT users who operate in the field of so-called "hard science"
(i.e., physics, chemistry, and mathematics). Nevertheless, this evolution has to deal with
several aspects (including data deluge, data integration, and scientific collaboration, just to
cite a few) and presents new challenges related to the proposal of innovative approaches in
the wide scenario of emergent ICT solutions.
This thesis aims at facing these challenges in the context of three case studies, being
each case study devoted to cope with a specific open issue by proposing proper solutions in
line with recent advances in computer science.
The first case study focuses on the task of unearthing and integrating information from
different web resources, each having its own organization, terminology and data formats in
order to provide users with flexible environment for accessing the above resources and
smartly exploring their content. The study explores the potential of cloud paradigm as an
enabling technology to severely curtail issues associated with scalability and performance
of applications devoted to support the above task. Specifically, it presents Biocloud Search
EnGene (BSE), a cloud-based application which allows for searching and integrating
biological information made available by public large-scale genomic repositories. BSE is
publicly available at: http://biocloud-unica.appspot.com/.
The second case study addresses scientific collaboration on the Web with special focus
on building a semantic network, where team members, adequately supported by easy
access to biomedical ontologies, define and enrich network nodes with annotations derived
from available ontologies. The study presents a cloud-based application called
Collaborative Workspaces in Biomedicine (COWB) which deals with supporting users in
the construction of the semantic network by organizing, retrieving and creating
connections between contents of different types. Public and private workspaces provide an
accessible representation of the collective knowledge that is incrementally expanded.
COWB is publicly available at: http://cowb-unica.appspot.com/.
Finally, the third case study concerns the knowledge extraction from very large datasets.
The study investigates the performance of random forests in classifying microarray data. In
particular, the study faces the problem of reducing the contribution of trees whose nodes
are populated by non-informative features. Experiments are presented and results are then
analyzed in order to draw guidelines about how reducing the above contribution.
With respect to the previously mentioned challenges, this thesis sets out to give two
contributions summarized as follows. First, the potential of cloud technologies has been
evaluated for developing applications that support the access to bioinformatics resources
and the collaboration by improving awareness of user's contributions and fostering users
interaction. Second, the positive impact of the decision support offered by random forests
has been demonstrated in order to tackle effectively the curse of dimensionality
«Tentare ogni mezzo onde riunirli». Polizia e conflitti familiari a Bologna nel XIX secolo
Get PDFMy dissertation analyzes the action pursued by the police in Bologna during the years of
Restoration in solving critical family situations through the use of a conciliatory attitude
that allowed for the avoidance of court intervention even in the presence of criminal
behavior. The Police took a non-repressive approach towards adultery, illegitimate
pregnancies, rape and other family disorders provided they didn’t implicate a public
scandal and, when they were called upon to settle disputes between spouses, police
officers always tried to maintain matrimonial stability as well as social peace. The sources
of my research were the numerous documents produced by the Direzione provinciale di
polizia between 1814 and 1859 that testify to the police's large involvement in cases of
matrimonial conflict: a rich and vivid source of material that provides the opportunity to
study how the different parties acted and interacted in a changing society such as Bologna
in the period following the restoration of papal power. The main aim has been to
investigate the origins of police choices and attitudes in the field of private life and to
develop a better understanding of policing in previous centuries where the origins of most
of the observed phenomena can be found. I devoted particular attention to non-judiciary
practices of peacemaking to compare them with the official way of dealing with family
disorder and to obtain a reliable frame of Nineteenth century police action
Un approccio multidisciplinare per l’identificazione dello stock del nasello (Merluccius merluccius, Linnaeus 1758) nei mari sardi
Get PDFThe “stock” concept is fundamental to fisheries management. To manage a fishery responsibly it is important to understand its stock structure and how fishing effort and mortality are distributed (Begg e Waldman, 1999). The failure to comply the true stock structure and the ineffective fisheries management of an exploited species can lead to overfishing and depletion of the stock (Begg et al., 1999a). In the last years, scientific community has pointed out that the most successful way to address stock identification studies is the application of a holistic approach, thus involving a broad selection of complementary techniques (Begg et al., 1999a; Abaunza, 2008a; Cadrin et al., 2013).
The European hake (Merluccius merluccius, Linnaeus 1758) represents a basic component of the demersal communities and one of the target species in the Mediterranean Sea (Lo Brutto et al., 2004; Ligas et al., 2011). For this reason it has been extensively studied. Furthermore, hake stocks are generally considered over-exploited both in the Atlantic Ocean (ICES, 2011; 2012) and in the Mediterranean Sea (STECF, 2013; GFCM, 2014). At present, European hake populations in the Mediterranean Sea are managed considering several relatively small geographical sub-areas (GSAs), which are identified mainly on the basis of political considerations (Ragonese et al., 2012; Vittori et al., 2013). In this partition, Sardinian seas are represented by GSAs 11.1 and 11.2 and are split between two FAO Statistical Divisions (Balearic Islands and Sardinia).
It is known that the complexity of many marine species stocks is often underestimated in modern stock management processes (Begg et al., 1999a). As regards the Mediterranean sea, various studies suggested a geographical distribution of the stocks that appears considerably different from the current management units partition (Abaunza et al., 2000; Abaunza et al., 2008c; Murta et al., 2008), and this fact have been observed also for the European hake (Castillo et al., 2004; Mattiucci et al., 2004; Tanner et al., 2012; Fiorentino et al., 2014).
The need of the achievement of a comprehensive knowledge about the stock structure of a commercially important species like M. merluccius, has led to the development of this study, which aims, through the employment of a multidisciplinary approach, at a better geographical definition of this species stock in the waters around Sardinia. A first insight into the complexity of the European hake population in the area has been supplied by the analysis and comparison of its length structure in the western and eastern coasts of Sardinia, showing a degree of differentiation that has been subsequently deepened through the application of various techniques.
The analysis of the variability in the growth of the species hasn’t indicated a meaningful differentiation of the populations in the two sides of the island, but has suggested that the presence of many spawning areas in the western coast could be the cause of the difference in the 0 age-class mean length obtained, as well as in the length structure above-mentioned.
On the contrary, the implementation of a geometric morphometric technique to study the shape of individuals has led to the discovery of a significant, even though of moderate extent, differentiation between the two coasts. However, as remarked by Tudela (1999) and Levi et al. (2004) in other case-studies, these differences were believed to be linked only to environmental influences, without a connection to those biological parameters that are fundamental in the definition of a stock. This hypothesis has been made also considering that the observed difference in shape didn’t seem to affect individuals’ growth.
Lastly, the parasitological exam of specimens collected in the whole area of Sardinian seas, has supported the hypothesis of homogeneity of the populations in the area. Indeed, no significant differences have been found in the relative abundance and prevalence of the various parasite taxa examined. Comparing these results with those obtained in a similar study carried out in the Mediterranean Sea (Mattiucci et al., 2004) it has been possible to highlight a considerable similarity of our study area with the central area of Mediterranean sea, and, conversely, a clear differentiation between Sardinian seas and the eastern part of Mediterranean basin. Similar considerations has been made in the context of StockMed project (Fiorentino et al., 2014).
This study has therefore provided a solid evidence of the homogeneity of the European hake stock in the waters around Sardinia, leading to the conclusion that this population should be managed jointly. Moreover, it has supported the recently expressed opinion that its stock (as well as those of other important species) could be wider than expected, underlining the need of improving current management units boundaries
Geochemical studies on antimony: antimony dispersion in water draining Su Suergiu mine area; removal of Sb(V) from aqueous solution by layered double hydroxides (LDH)
Get PDFAntimony (Sb) is considered a pollutant of priority interest, it is largely used in several industrial sectors (> 100,000 tons year worldwide) and is heavily mined worldwide (Leuz et al., 2006). In this work the hydrogeochemical behavior of Sb has been studied in water draining the abandoned antimony mine of Su Suergiu, SE Sardinia. Waters flowing at Su Suergiu show high Sb concentration and impact the main river of South Sardinia, the Flumendosa River that supplies water for agricultural and domestic uses. The main source of contamination at Su Suergiu is represented by the foundry slag heaps, in fact the slag drainages contain up to 30,000 μg L-1 Sb(tot) (median value 13,000 μg L-1 Sb(tot)). The determination of Sb specie in solution has been carried out through the analyses of both Sb(tot) (by ICP-MS and/or ICP-OES) and Sb(III) (by ASV). The Sb(III) concentration was determined on filtered (pore-size 0.45 μm) water samples stabilized with L(+) tartaric acid plus nitric acid, that, among several stabilizations of Sb(III) tested, has been evaluated as the most effective. Results obtained, showed that Sb(V) prevails in water sampled at Su Suergiu and surrounding area as Sb(OH)6̄ species, in agreement with the circumneutral-slightly alkaline pH values and oxidizing condition (Sb(III) ≤6% of Sb(tot)). The Sb(V) is less toxic but more mobile than Sb(III); the Sb behavior in water analyzed seems to be conservative, and the most important natural attenuation process of Sb contamination appears to be dilution. First in the water of Riu Ciurixeda (whose catchment collect all mine drainage), and after in the Flumendosa River, the Sb concentration decreases significantly, from 104 to 101 μg L-1, but in the Flumendosa River it still exceeded the limit recommended by both the World Health Organization (20 μg L-1) and the European Union (5 μg L-1), especially under extremely high flow conditions (Sb(tot) = 51 μg L-1; median relative to all flow conditions Sb(tot) = 22 μg L-1).
In view of these results Sb(V) removal from solution was tested using a synthetic mineral belonging to the class of layered double hydroxides, that has the advantage, with respect to the other sorbents (metal oxy-hydroxides, organic polymers, etc...), of being able to remove contaminants from solutions at circumneutral pH values often found in the environment. The LDH are characterized by a layered structure composed by brucite-like sheets ([M2+1-xM3+x(OH)2]x+), stacked along the c axis and positively charged, due to the partial substitution of bivalent cations (M2+ = Mg2+, Zn2+, Ca2+) by trivalent cations (M3+ = Al3+, Fe3+). The positive charges are compensated by anions or anionic complexes (An- = Cl-, NO3-, CO32-) in the interlayer, where also structural water can occur. From an environmental point of view, LDH have anion exchange capacity, sorption capacity, high specific surface area and the “memory effect”, which is the capacity of the calcined phases which have undergone structural collapse from the loss of interlayer water and anions, to recover its structure when immerged in aqueous solution. Calcined and nitrate LDH were tested; the calcined resulted are the most effective. Among them the Mg(AlFe)-c oxides, derived from the calcination of hydrotalcite-like compounds {Mg6Al2(OH)16CO3∙4H2O}, removed Sb(OH)6̄ from solution through the rehydration and formation of a
brandholzite-like compound {Mg[Sb(OH)6]2·6H2O}. The 2ZnAl-c oxides derived from the calcination of zaccagnaite-like compounds (Zn4Al2(OH)12CO3∙3H2O) kept Sb(OH)6̄ from solution by its intercalation in the interlayer during the reconstruction of zincalstibite-like LDH {Zn2Al(OH)6[Sb(OH)6]}. The Sb(OH)6̄ removal capacity of both sorbents is seriously affected by the presence of coexistent equal concentrations of As in solution, while the carbonate species and the SO42- result lower competition with respect to Sb(OH)6̄. Sorption tests with selected calcined LDH, Mg(AlFe)-c and 2ZnAl-c, were performed on water collected in the slag drainage of Su Suergiu, characterized by slightly alkaline pH and high concentration of SO42- (1006 mg L-1), HCO3̄ (485 mg L-1), As (3386 μg L-1) and Sb(tot) (9900 μg L-1). Results show substantial capacity of Sb removal from solution, and also of As. Due to the relatively low concentration of Sb in Su Suergiu water with respect to the synthetic solution used in the sorption test, the main removal process of Sb resulted for both sorbents used in the intercalation in the interlayer during the reconstruction of carbonate(hydroxyl) LDH structure, also As seem to be removed through the same mechanism. In several experiments the dissolution of sorbents was observed, therefore it is necessary consider the impact from the dissolution of the metals composing them.
The solid/liquid ratio strongly influences the removal processes, therefore future studies should address this aspect to assess the potential use of LDH in Sb removal from solution at circumneutral pH usually found in the environment
Analisi diacronica, pedogeochimica ed etnopedologica per lo studio dell’evoluzione storico-territoriale e delle condizioni attuali dei suoli e del paesaggio. La fascia costiera dell’Ambito di Paesaggio “Golfo di Oristano”(Sardegna centro-occidentale)
Get PDFThis research aims to show a possible integrated approach to the study of the coastal zone
of the Gulf of Oristano, characterized by a complex and delicate environmental system and
a production context historically significant in terms of agriculture. The purpose is to
propose a tool for knowledge of the area through the analysis of the existing relationship
between:
- the landscape and its transformations, mostly related to the use and land cover;
- the soil, which is one of the fundamental components of the landscape;
- local knowledge expressed with toponyms (place names), which are often
originated by the characteristics of the landscape to which they relate and
contribute to the formation of the social representation of a territory.
The starting point of the study has been the consciousness that in the last century the study
area has undergone an intense transformation. A careful analysis of the evolutionary
processes of land use and landscape has been performed, based on comparison of historical
and geographical information of maps and orthophotos available for the study area, in
order to understand the historical matrix of the landscape and recognize the stays and the
changes imposed on the territory as a result of the man-environment interaction.
Specifically, the study area has undergone a deep reconfiguration mainly due to the
activities of land reclamation and to important changes towards the artificial land use of
previously agricultural or natural/semi-natural areas. The soil consumption has been
defined, as well as on a quantitative basis, also on the basis of the quality of the soils
affected by the process of consumption. Soils mostly consumed in the period considered
(1954-2008) belong to the intermediate classes of land capability.
Bearing in mind that the soil functions can be defined in terms of chemical, physical and
biological properties and related processes, the present study (carried out in collaboration
with national and foreign research institutions) has determined in first analysis the
parameters that give a general idea of the specific environmental system under study
(physico-chemical analysis) and then has proceed with more specific surveys (biochemical
analysis and analysis on PTEs - Potentially Toxic Elements), in order to perform a
screening of the “state of health” and define the quality of soil in relation to different uses.
The physico-chemical and pedo-geochemical survey has allowed to determine the quality
level of the investigated soils and to differentiate the anthropic or geogenic/pedogenic
origin of potential contaminants (Pb, Zn, Cd, Cu, Ni and As). It has been found that in the investigated area there is a form of punctual contamination
quite limited and certainly not widespread. The data processing has showed that, with the
exception of areas in which the contamination is clearly anthropic (River Sitzerri valley) or
where the contamination is supposed (areas locally contaminated by Cu), the main factors
that control the distribution and the concentration of PTEs in the study area are related to
natural geological and pedological conditions.
The evaluation of the effects of land use on soil quality has been based on the
determination of biochemical parameters used as indicators of soil quality in response to
land use representative of the study area (agricultural fields, Mediterranean scrub, garrigue,
eucalyptus plantations, stands of pine, uncultivated).
The biochemical analysis have examined the determination of enzymatic activities related
to four soil enzymes (dehydrogenase, indicative of overall metabolic activities of
microorganisms in soil and beta-glucosidase, phosphatase and protease, hydrolytic
enzymes connected to the carbon, nitrogen and phosphorus cycle) and the determination of
glomalin (glycoprotein produced by arbuscular mycorrhizal fungi).
It has been found that the variations in the measured enzymtic activities and glomalin are
related to the diversity of land uses. These parameters indeed increase mainly as a function
of the input of organic matter and of the availability of substrates, and decrease in function
of anthropic interference, showing always medium-low values in soils under stands of pine
and agricultural fields, while high values are always related to the Mediterranean scrub and
the eucalyptus plantations.
Moreover in the research, in the light of the fact that the landscape (of which the soil is an
integral part) can be considered as a mirror of all the local knowledge and perceptions of
the lived space, it has been investigated through an ethno-pedologic integrated approach on
the meaning and distribution of toponyms, with particular reference to those related to the
soil resources (pedonyms) of the 14 municipalities bordering the coastal zone of the Gulf of
Oristano.
This approach has helped to identify the correspondence between local knowledge
(deduced from the meaning of toponyms) and the scientific one (analytical parameters and
information related to soil classification). The most important result of the research
provides statistical evidence of the fact that the inhabitants of the study area, although not
possessing the appropriate scientific expertise (at least in the past), have tried over time to
distinguish the various types of soil and give them a name according to the characteristics
of the soil especially related to fertility, the knowledge of which allowed to make the best use of the soils for agricultural purposes
Exploitation of Ebola Virus VP35 Protein to identify new drugs counteracting its type I IFN antagonism
Get PDFEbolaviruses (EBOVs) are among the most virulent and deadly pathogens ever known, causing fulminant haemorrhagic fevers in humans and non-human primates. The 2014 outbreak of Ebola virus disease (EVD) in West Africa has claimed more lives than all previous EVD outbreaks combined. The EBOV high mortality rates have been related to the virus-induced impairment of the host innate immunity reaction due to two virus-coded proteins, VP24 and VP35. EBOV VP35 is a multifunctional protein, it is essential for viral replication as a component of the viral RNA polymerase and it also participates in nucleocapsid assembly. Early during EBOV infection, alpha-beta interferon (IFN-α/β) production would be triggered upon recognition of viral dsRNA products by cytoplasmic retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs). However, this recognition is efficiently prevented by the double-stranded RNA (dsRNA) binding activity of the EBOV VP35 protein, which hides RLRs binding sites on the dsRNA phosphate backbone as well the 5’-triphosphate (5’-ppp) dsRNA ends to RIG-I recognition. In addition to dsRNA binding and sequestration, EBOV VP35 inhibits IFN-α/β production preventing the activation of the IFN regulatory factor 3 (IRF-3) by direct interaction with cellular proteins. Previous studies demonstrated that single amino acid changes in the VP35 dsRNA binding domain reduce EBOV virulence, indicating that VP35 is an attractive target for antiviral drugs development. Within this context, here we report the establishment of a novel method to characterize the EBOV VP35 inhibitory function of the dsRNA-dependent RIG-I-mediated IFN-β signaling pathway in a BLS2 cell culture setting. In such system, a plasmid containing the promoter region of IFN-β gene linked with a luciferase reporter gene was transfected, together with a EBOV VP35 mammalian expression plasmid, into the IFN-sensitive A549 cell line, and the IFN-induction was stimulated through dsRNA transfection. Through alanine scanning mutational studies with biochemical, cellular and computational methods we highlighted the importance of some VP35 residues involved in dsRNA end-capping binding, such as R312, K282 and R322, that may serve as target for the development of small-molecule inhibitors against EBOV. Furthermore, we identified a synthetic compound that increased IFN-induction only under antiviral response stimulation and subverted VP35 inhibition, proving to be very attractive for the development of an antiviral drug. In conclusion, our results provide the establishment of a new assay as a straightforward tool for the screening of antiviral compounds that target i) dsRNA-VP35 or cellular protein-VP35 interaction and ii) dsRNA-dependent RIG-I-mediated IFN signaling pathway, in order to potentiate the IFN response against VP35 inhibition, setting the bases for further drug development
Development of a methodology for spatial composite indicators: a case study on landscape.
Get PDFThis thesis proposes a methodology for the construction of spatial composite indicators (SCI). The study starts from the premise that Composite Indicators (CIs) are regarded as very reliable tools to support decision processes. They are usually developed to describe complex phenomena of the reality in various domains, and more specifically, to rank spatial units (usually countries) in which a given indicator is calculated. Despite their wide use and their development, no attention has generally been paid to the spatial dimension of their input data and of their final score. Data are treated as normal statistical sampling, therefore their spatial structure and their spatial importance are considered to be equal across the spatial domain, without considerations about possible spatial variations. Nowadays, this appears to be a serious limit, considering the development of Spatial Data Infrastructures (SDI), which makes a large amount of spatial data available, and the development of spatial statistical techniques implemented in GIS, with combined together offer unprecedented opportunity for the spatialization of CIs
Sicurezza alimentare di prodotti ortofrutticoli di IV gamma
Get PDFIntroduction
Vegetables are major components of healthy and balanced diet. However, 25% of foodborne
diseases are linked to the consumption of vegetables, especially the minimally processed ready to
eat (RTE) vegetables. The main foodborne pathogens associated at RTE vegetables are
Enterobacteriaceae (E. coli, Salmonella spp. and Yersinia spp.) and psychrophilic microorganisms
like Listeria monocytogenes.
Aim of study
The aim of this work was to assess the microbiological risks associated with consumption of RTE
salads, through the quantification of microbiological contamination. In addition we carried out the
rapid detection of foodborne pathogens by real time PCR, and molecular characterization of Listeria
monocytogenes strain isolated in this study. Microbiological and bio molecular challenge tests was
carried out for assess potential growth of Listeria monocytogenes in vegetables stored at different
temperatures. Besides, the work was focused on the evaluation of washing process in association to
the shelf life of these products.
Materials and methods
A total of 300 pre-packaged mixed raw vegetable salads collected from retail premises (68%) and
production plants (32%) were examined. Microbiological eligibility for human consumption (Reg
CE 1441/2007) is based on three bacteriological parameters (Escherichia coli, Salmonella spp and
L. monocytogenes). In order to assess the safety of RTE vegetables, all parameters required by law
have been investigated. The contamination of vegetables from E. coli O157:H7, L. monocytogenes
and Salmonella spp was also investigated by real time PCR. Furthermore, the pathogenic properties
of L. monocytogenes have been evaluated by PCR assay (prfA, rrn, hlyA, actA, inlA, inlB, iap, plcA
e plcB). The purpose of Challenge test was to provide information especially on the behavior of L.
monocytogenes.
Results and conclusion
Parsley and mixed salads showed the most contaminated panel, however we found high levels of
contamination by Enterobacteriaceae in every kind of RTE salads. Salmonella spp. and E. coli
O157:H7 have never been isolated, while only a sample of rocket was contaminated by one strain of
L. monocytogenes and Yersinia enterocolitica. The PCR assay showed the virulence genes of L.
monocytogenes strain (prfA, rrn, actA, inlA, inlB, plcA, plcB). Washing temperature,
microbiological quality of water and raw material are basic requirements to achieve high
microbiological standards for RTE salads. Listeria monocytogenes shows a growth potential
variable in consideration of the different types of products and storage temperatures. Bio molecular
challenge tests appear a useful tool for the evaluation of the survival of L. monocytogenes when
coltural results seem uncertain (eg. high or low bacterial growth and difficulty in estimating the
growth plate)