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Stéréotype explicite et implicite des personnes porteuses de trisomie 21. Relations entre typicalité du visage, jugement sur l'intelligence et niveau cognitif / Explicit and implicit stereotyping of trisomy 21. Relationships between typicality of faces, judgment of intelligence and cognitive level.Enéa Drapeau, Claire 20 December 2012 (has links)
La trisomie 21 (t21) est l'anomalie génétique la plus fréquente à l'origine d'une déficience intellectuelle. Bien que la recherche concernant le stéréotype social de la t21 soit limitée, les personnes porteuses de t21, et particulièrement les enfants, semblent être associées à des traits de personnalité tels que « affectueux » et « heureux », les caractéristiques positives l'emportant sur les négatives comme « retardé ». Cependant, ce stéréotype positif coexiste avec des attitudes ambivalentes notamment à propos de l'intégration scolaire de ces enfants. L'objectif principal de cette thèse est d'étudier ce stéréotype au niveau implicite ainsi que l'impact des caractéristiques faciales sur le stéréotype au niveau explicite et implicite. Nos résultats confirment d'une part, un stéréotype social positif explicite dans des échantillons d'étudiants, d'adultes non étudiant et de professionnels du handicap intellectuel. Les visages d'enfants présentant plus de traits faciaux associés à la t21 sont associés à un stéréotype moins positif que ceux en présentant moins. D'autre part, nous mettons en évidence un stéréotype négatif au niveau implicite, même chez les professionnels du handicap. Nous étudions l'influence des variables individuelles sexe, familiarité avec la t21 et théories implicites de l'intelligence sur le stéréotype explicite et implicite. Puis, nous montrons une relation négative entre la typicalité des visages et le jugement sur l'intelligence alors que nous n'observons pas de relation significative entre la typicalité des visages et le niveau cognitif. Nous discutons l'implication de ces résultats sur l'étude du stéréotype et sur les personnes stigmatisées. / Trisomy 21 (t21) or Down syndrome is the most frequent genetic disorder associated with intellectual disability. Although research on the social stereotype toward t21 is very limited, it seems that persons with t21 are typically viewed as “affectionate” and “happy”; with positive personality traits prevailing over the negative ones (e.g., “mentally retarded”). However, this positive stereotype coexists with ambivalent attitudes. The main objective of this study was to investigate the stereotype at the implicit level and the impact of t21 facial features on the stereotype of t21 at the both explicit and implicit levels. Our results confirm, on one hand, a positive social stereotype explicit in samples of young adult students, non-student adults and professional caregivers working with intellectually disabled persons. The positive bias typically found in explicit judgments of children with t21 is smaller for those whose facial features are highly characteristic of this disorder, compared to their counterparts with less distinctive features and to typically developing children. On the other hand, we also show that this bias can coexist with negative evaluations at the implicit level, even among professional caregivers but to a lesser extent. We study the influence of individual variables sex, familiarity with the t21 and implicit theories of intelligence on explicit and implicit stereotypes. Finally, we show a negative relationship between t21 typicality of faces and the judgment of the intelligence as we do not observe a significant relationship between typicality and the cognitive level. We discuss the implications of these results.
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Analýza emocionálních stavů na základě obrazových předloh / Emotional State Analysis Upon Image PatternsPřinosil, Jiří January 2009 (has links)
This dissertation thesis deals with the automatic system for basic emotional facial expressions recognition from static images. Generally the system is divided into the three independent parts, which are linked together in some way. The first part deals with automatic face detection from color images. In this part they were proposed the face detector based on skin color and the methods for eyes and lips position localization from detected faces using color maps. A part of this is modified Viola-Jones face detector, which was even experimentally used for eyes detection. The both face detectors were tested on the Georgia Tech Face Database. Another part of the automatic system is features extraction process, which consists of two statistical methods and of one method based on image filtering using set of Gabor’s filters. For purposes of this thesis they were experimentally used some combinations of features extracted using these methods. The last part of the automatic system is mathematical classifier, which is represented by feed-forward neural network. The automatic system is utilized by adding an accurate particular facial features localization using active shape model. The whole automatic system was benchmarked on recognizing of basic emotional facial expressions using the Japanese Female Facial Expression database.
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ATTENTION TO SHARED PERCEPTUAL FEATURES INFLUENCES EARLY NOUN-CONCEPT PROCESSINGRyan Peters (7027685) 15 August 2019 (has links)
Recent modeling work shows that patterns of shared perceptual features relate to the group-level order of acquisition of early-learned words (Peters & Borovsky, 2019). Here we present results for two eye-tracked word recognition studies showing patterns of shared perceptual features likewise influence processing of known and novel noun-concepts in individual 24- to 30-month-old toddlers. In the first study (Chapter 2, N=54), we explored the influence of perceptual connectivity on both initial attentional biases to known objects and subsequent label processing. In the second study (Chapter 3, N=49), we investigated whether perceptual connectivity influences patterns of attention during learning opportunities for novel object-features and object-labels, subsequent pre-labeling attentional biases, and object-label learning outcomes. Results across studies revealed four main findings. First, patterns of shared (visual-motion and visual-form and surface) perceptual features do relate to differences in early noun-concept processing at the individual level. Second, such influences are tentatively at play from the outset of novel noun-concept learning. Third, connectivity driven attentional biases to both recently learned and well-known objects follow a similar timecourse and show similar patterns of individual differences. Fourth, initial, pre-labeling attentional biases to objects relate to subsequent label processing, but do not linearly explain effects of connectivity. Finally, we consider whether these findings provide support for shared-feature-guided selective attention to object features as a mechanism underlying early lexico-semantic development.
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Processing of Sub-micrometer Features for Rear Contact Passivation Layer of Ultrathin Film Solar Cells Using Optical LithographyRoxner, Evelina, Olsmats Baumeister, Ronja January 2019 (has links)
Thin film copper, indium, gallium, selenide (CIGS) solar cells are promising in the field of photovoltaic technology. To reduce material and fabrication cost, as well as increasing electrical properties of the cell, research is ongoing towards ultra-thin film solar cells (absorption layer thickness less than 500 nm). Ultra-thin CIGS solar cells has shown a decrease in interface recombination and improved optical properties when adding a rear contact passivation layer of aluminium oxide. In this work, the process of creating sub-micrometer features of a passivation layer using conventional optical lithography is investigated. To specify, the objective was to optimize the development conditions in the optical lithography process when fabricating equidistant line contacts in aluminium oxide with 800 nm feature size. It was found that line contacts with smaller feature sizes require longer development time, than line contacts with larger feature sizes. The experiments conducted showed that the pre-set development and exposure conditions used by the NOA group are not optimized for 800 nm or smaller line contacts. Further, for the optical lithography process, silicon substrates are not comparable with substrates of soda lime glass coated with molybdenum. Slight underdevelopment of a sample, showed line contacts smaller than the resolution of the laser used in the exposure – suggesting an alternative method of processing small line contacts with optical lithography.
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Jsou velikost těla a druhově specifické zbarvení důležitými znaky pro rozpoznávání predátorů potenciální kořistí? / Are body size and specific species colouration important cues for predator recognition by their potencial prey? Diplomová práceAntonová, Kateřina January 2018 (has links)
I tested influence of a body size and overal colouration in feeders experiments on recognition of sparrowhawk (Accipiter nisus) by chosen species of passerine. Experiments were conducted in years 2015 ̶ 2018. I used a plush dummies which carried a specific featuress of raptor (hooked beak, claws) and specific features of genus Accipiter (yellow eyes, respectively yellow eyes and overal colouration). As a control, dummy of harmless pigeon was used. Smaller dummies (size of a great tit) were not recognized as a raptor regardless of colouration. Large dummies with colouration of great tit and pigeon were not recognized as a raptor as well. On a contrary, large dummy with colouration of robin was recognized as a raptor, respectively sparrowhawk. Most birds who were flying to the feeders, at first payed attention to global features (size, overal colouration). If these features belong to well-known harmless bird, then local features (particular) which characterize raptor or sparrowhawk had no effect. Birds did not pay attention to them. Therefore it depends on a context, in which potential local key features occure.
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Analyse acoustique de la voix émotionnelle de locuteurs lors d’une interaction humain-robot / Acoustic analysis of speakers emotional voices during a human-robot interactionTahon, Marie 15 November 2012 (has links)
Mes travaux de thèse s'intéressent à la voix émotionnelle dans un contexte d'interaction humain-robot. Dans une interaction réaliste, nous définissons au moins quatre grands types de variabilités : l'environnement (salle, microphone); le locuteur, ses caractéristiques physiques (genre, âge, type de voix) et sa personnalité; ses états émotionnels; et enfin le type d'interaction (jeu, situation d'urgence ou de vie quotidienne). A partir de signaux audio collectés dans différentes conditions, nous avons cherché, grâce à des descripteurs acoustiques, à imbriquer la caractérisation d'un locuteur et de son état émotionnel en prenant en compte ces variabilités.Déterminer quels descripteurs sont essentiels et quels sont ceux à éviter est un défi complexe puisqu'il nécessite de travailler sur un grand nombre de variabilités et donc d'avoir à sa disposition des corpus riches et variés. Les principaux résultats portent à la fois sur la collecte et l'annotation de corpus émotionnels réalistes avec des locuteurs variés (enfants, adultes, personnes âgées), dans plusieurs environnements, et sur la robustesse de descripteurs acoustiques suivant ces quatre variabilités. Deux résultats intéressants découlent de cette analyse acoustique: la caractérisation sonore d'un corpus et l'établissement d'une liste "noire" de descripteurs très variables. Les émotions ne sont qu'une partie des indices paralinguistiques supportés par le signal audio, la personnalité et le stress dans la voix ont également été étudiés. Nous avons également mis en oeuvre un module de reconnaissance automatique des émotions et de caractérisation du locuteur qui a été testé au cours d'interactions humain-robot réalistes. Une réflexion éthique a été menée sur ces travaux. / This thesis deals with emotional voices during a human-robot interaction. In a natural interaction, we define at least, four kinds of variabilities: environment (room, microphone); speaker, its physic characteristics (gender, age, voice type) and personality; emotional states; and finally the kind of interaction (game scenario, emergency, everyday life). From audio signals collected in different conditions, we tried to find out, with acoustic features, to overlap speaker and his emotional state characterisation taking into account these variabilities.To find which features are essential and which are to avoid is hard challenge because it needs to work with a high number of variabilities and then to have riche and diverse data to our disposal. The main results are about the collection and the annotation of natural emotional corpora that have been recorded with different kinds of speakers (children, adults, elderly people) in various environments, and about how reliable are acoustic features across the four variabilities. This analysis led to two interesting aspects: the audio characterisation of a corpus and the drawing of a black list of features which vary a lot. Emotions are ust a part of paralinguistic features that are supported by the audio channel, other paralinguistic features have been studied such as personality and stress in the voice. We have also built automatic emotion recognition and speaker characterisation module that we have tested during realistic interactions. An ethic discussion have been driven on our work.
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Effekten kvinnliga styrelseledamöter och ämbetstid i styrelsen har på CSR samt kulturella skillnaders inverkan på sambanden : En kvantitativ studie på 704 börsnoterade företag i USA samt 598 börsnoterade företag i Europa / The impact of female board members and board tenure have on CSR and cultural differences on these relationshipAndersson, Celine, Eriksson, Louise January 2019 (has links)
Sammanfattning Titel: Effekten kvinnliga styrelseledamöter och ämbetstid i styrelsen har på CSR samt kulturella skillnaders inverkan på sambanden Nivå: Examensarbete på Grundnivå (kandidatexamen) i ämnet företagsekonomi. Författare: Celine Andersson och Louise Eriksson. Handledare: Jan Svanberg. Datum: 2019 – Juni. Syfte: På grund av påtryckningar från samhället har företagens intresse för CSR-aktiviteter på senare år ökat, och även skapat reglering och restriktioner kring detta. Ansvaret för att dessa regler och restriktioner efterföljs är styrelsens, där styrelsens agerande kan bero på dess sammansättning. Studien syftar till att undersöka om kvinnliga styrelseledamöter samt ämbetstiden i styrelsen kan ha en påverkan på företagens CSR genom ändrat intresse i dess CSR-aktiviteter, och även se om kulturella skillnader har en inverkan på ett eventuellt samband. Metod: Studien har en positivistisk utgångspunkt med en hypotetisk-deduktiv ansats. Forskningsstrategin som studien utförs inom är kvantitativ, där data angående kvinnliga styrelseledamöter, ämbetstid i styrelsen och CSP hämtats från 598 respektive 704 företag från Europa respektive USA, vilket resulterat i 2990 respektive 3520 observationer under femårsperioden 2013-2017. För insamling av datan har vi använt databasen Thomson Reuters Datastream. Vi har även hämtat data angående nationers kulturella skillnader från Hofstede Insights, med hjälp av Country Comparison Tool. Sammanställning av datan har skett med hjälp av statistikprogrammet SPSS. Resultat & slutsats: Det resultat studien kommer fram till är att det finns ett positivt samband mellan kvinnliga styrelseledamöter och CSR. Vi ser att ämbetstiden i styrelsen har en liten effekt på CSR, men här behövs det ytterligare forskning. Kulturella skillnader kan vi fastställa har en modererande effekt på båda ovanstående samband. Examensarbetets bidrag: Bidraget som studien ger är en ökad kunskap kring hur styrelsens ämbetstid påverkar företagets CSR, den ger även en påbörjad fyllnad av forskningsgapet som finns kring hur kulturella skillnader påverkar sambandet. Vidare har vi ökat ett säkerställande av det positiva sambandet mellan kvinnliga styrelseledamöter och CSR, samt fastslagit att kulturella skillnader påverkar kvinnliga styrelseledamöters makt gällande CSR, samt hur ämbetstiden i styrelsen påverkar beslut kring CSR. Förslag till fortsatt forskning: För framtida forskning på ämnet efterfrågar vi studier för den optimala andelen kvinnliga styrelseledamöter och var gränsen går för att det positiva sambandet mellan kvinnliga styrelseledamöter och CSR blir svagare. Vidare forskning på ämnet kan även vara att djupare studera om ämbetstiden har en påverkan på företagets CSR. Nyckelord: Kvinnliga styrelseledamöter, ämbetstid i styrelsen, kulturella skillnader, CSP, CSR, Hofstede och ESG. / Abstract Title: The impact of female board members and board tenure have on CSR and cultural differences on these relationship Level: Student thesis, final assignment for Bachelor Degree in Business Administration Author: Celine Andersson and Louise Eriksson Supervisor: Jan Svanberg Date: 2019 - June Aim: Due to pressure from the society, companies interest in CSR activities has increased in recent years, and has also caused regulation and restrictions on this. The board is responsible for ensuring that these rules and restrictions are complied with, where the boards actions may depend on its composition. This study aims to investigate whether female board members and the board tenure can have an impact on the companies CSR through a changed interest in the the companies CSR-activities, and also see if cultural differences might have an impact on a possible relationship. Method: The study has a positivistic starting point with a hypothetical-deductive approach. The research strategy in which the study is conducted is quantitative, where data on female board members, board tenure and CSP were obtained from 598 and 704 companies from Europe and the US, which resulted in 2990 and 3520 observations during the five-year period 2013-2017. For data collection, we have used the Thomson Reuters Datastream database. We have also collected data on nations' cultural differences from Hofstede Insights, using the Country Comparison Tool. Compilation of the data has been made using the statistical program SPSS. Result & Conclusions: The result we found in the study is that there is a positive correlation between female board members and CSR. We can see that the board tenure has a small effect on CSR, but here further research is needed. Furthermore, we can determine that cultural differences have a moderating effect on both of the above relationships. Contribution of the thesis: The contribution that the study provides is an increased knowledge of how board tenure affects the company's CSR, it also provides a commenced filling of the research gap that exists about how cultural differences affect the relationship. Furthermore, we have increased the assurance of the positive relationship between female board members and the CSR and has established that cultural differences affect the power of women board members regarding CSR, and how the board tenure affects decisions about CSR. Suggestions for future research: For future research on the subject, we demand studies for the optimal proportion of female board members and where the limit goes for the positive relationship between female board members and CSR to be weaker. Further research on the subject can also be on whether the board tenure has an impact on the company's CSR. Key words: Women on boards, board tenure, cultural features, CSP, CSR, Hofstede and ESG.
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Um estudo sobre os determinantes do atraso escolar / A study about determinants of schooling delayHonda, Kátia Morinaga 26 March 2007 (has links)
O objetivo desse trabalho é verificar a influência das características familiares no atraso escolar. O atraso escolar no Brasil, além de onerar os gastos do governo, representa baixo nível de capital humano acumulado nas crianças. Baixos níveis de capital humano acumulado representam indivíduos com habilidades mal desenvolvidas que atingem baixos níveis de produtividade dificultando o processo de desenvolvimento sustentável do país. O capital humano acumulado é resultado de um processo construtivo que depende do desenvolvimento do indivíduo no período anterior, portanto melhores desempenhos futuros são resultados de maior acúmulo de capital humano. A característica do processo sugere grande influência das características familiares. A família é o principal responsável por fornecer recursos durante os primeiros anos do processo de acúmulo de capital humano. O método utilizado para estimar o atraso escolar foi a quase verossimilhança em dois estágios, devido à natureza de contagem e à presença da variável endógena. O resultado obtido mostrou a influência da educação da mãe e do pai de forma a diminuir o atraso escolar e a diferença em magnitude em relação às estimações padrão. A variável renda, nesse método, apresentou impacto favorável ao atraso escolar. / The objective of this thesis is to verify the influence of family characteristics in schooling delay. The schooling delay in Brazil increases government?s spent and implies lower rate human capital accumulation on children. Lower rates of human capital accumulation means children will grow into less skilled workers, with low levels of productivity, which has a negative effect on development. The accumulation of human capital is a process that depends of the individual?s development throughout her life. The study considers family factors that have an evident influence in children development, reinforcing that the family is one of the main sources in the process of accumulative human capital. The variable used as proxy to human capital accumulation was schooling delay, which is a count variable and is clearly to endogeneity. The approach in this thesis is referred to as the two-stage quasi likelihood. Results obtained indicate that Parent?s education have a negative effect in the child?s being behind at school, while household income has a positive effect. Additionally, the difference in magnitude when compared with standard estimation methods is significant.
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Isolamento e caracterização de bactérias degradadoras de acefato. / Isolation and characterization of acephate degrading bacteria.Góes, Karina Paschoal 29 May 2009 (has links)
Quatro linhagens capazes de crescer com acefato foram isoladas a partir de solos com históricos de aplicação de deste composto. Stenotrophomonas maltophilia, Rhodococcus sp., Staphylococcus sp. e Pandoreae sp. foram identificadas através do rDNA 16S e perfil de ácidos graxos de membrana. Rhodococcus sp. foi o isolado mais eficiente na degradação de acefato, removendo 99.24% deste composto em meio de cultura com acefato como única fonte de carbono. Quando avaliado com acefato como fonte combinada de carbono e nitrogênio, este organismo degradou 19% de acefato com formação de metamidofós (17%). Staphylococcus sp. apresentou 21% de degradação de acefato utilizando-o como fonte de carbono e nitrogênio, mas não manteve o crescimento com este composto como fonte de carbono. Stenotrophomonas maltophilia e Pandoreae sp. não mantiveram crescimento com acefato como única fonte de carbono isoladamente. Estas linhagens apresentaram crescimento em acefato como fonte de nitrogênio e enxofre, porém, as análises de GC/MS demonstraram que não houve degradação nestas condições. / Four strains of microorganisms capable of growth on acephate were isolated from soil samples with a history of acephate application. Stenotrophomonas maltophilia, Rhodococcus sp., Staphylococcus sp. and Pandoreae sp. were identified based on 16S rRNA gene sequencing and fatty acid profiling. Rhodococcus sp. was the most efficient acephate degrader of the isolates, it removed 99.24% of acephate from defined growth media when the compound was provided as sole carbon source. When provided as a combined carbon and nitrogen source, the organisms degraded 19% of acephate with formation of methamidophos (17%). Staphylococcus sp. degraded 21% of acephate when provided as sole nitrogen and carbon source but did not grow on the compound as a sole source of carbon. Pandoreae sp. and Stenotrophomonas maltophilia failed to grow on acephate as sole source of carbon in defined medium. These strains grew in media where the pesticide was provided as a combined nitrogen and carbon source, but no acephate biodegradation could be demonstrated in these instances.
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Caracterização de Escherichia coli produtoras de toxina de Shiga (STEC) isoladas na produção de bovinos de cortes e nas respectivas carcaças dos animais abatidos / Characterization of Escherichia coli producing toxins Shiga (STEC) isolated in the production of beef cattle and in the carcasses of their animals slaughteredLaer, Ana Eucares von 02 February 2009 (has links)
Escherichia coli produtoras de toxina de Shiga (STEC) são consideradas importantes patógenos de origem alimentar que apresentam o trato intestinal de ruminantes domésticos, principalmente bovinos, seu reservatório natural. Esses microrganismos estão associados a doenças severas em humanos, tais como colíte hemorrágica (CH) e síndrome urêmica hemolítica (SHU). Este trabalho teve como objetivos avaliar a ocorrência de STEC em diferentes fontes, ambientais ou não, da criação e abate de bovinos confinados. Além disso, detectar a presença dos genes stx1, stx2, ehxA e eaeA; identificar cepas O157:H7 através da pesquisa do gene uidA; evidenciar a capacidade de produção de Stx e de Eh; identificar variantes de stx e de eaeA; e determinar os sorotipos e a diversidade genética das cepas de STEC. A avaliação da presença dos genes (stx1, stx2, ehxA, eaeA e uidA) e da produção de Eh foi utilizada como triagem para a seleção de cepas possivelmente patogênicas, sendo que do total de 628 isolados avaliados, foram selecionadas 50 cepas STEC e 12 consideradas como EPEC atípicas. Das STEC, 76% foram isolados provenientes de amostras de fezes, enquanto 18% foram de amostras de carcaças e 6% de amostras de água da baia. Seis cepas isoladas de fezes e 1 de carcaça foram sorotipificadas como O157:H7, todas positivas para a presença do gene uidA. Além do sorogrupo O157, nenhum outro, dentre os principais causadores de surtos e casos esporádicos de CH e SHU, foi detectado. Das 30 cepas que apresentaram resultado positivo no ensaio de citotoxicidade em células Vero, 96,7% apresentaram gene para a produção de Stx. Em 17 das STEC foi possível identificar o tipo de Stx produzida, através de ensaio imunocromatográfico, sendo que todas apresentaram os genes correspondentes à toxina identificada, com exceção de uma cepa de carcaça que foi positiva para a produção de ambas as toxinas, mas apresentando apenas o gene stx2. Através da análise por PFGE, observou-se a disseminação e permanência de cepas STEC entre os animais. Dentre as 50 cepas STEC, 28% foram positivas para a variante Stx2d ativável e das 21 cepas eaeApositivas apenas em 8 foram detectadas variantes desse gene, sendo 7 positivas para eae-γ e a outra cepa positiva para eae-β). Através dos resultados obtidos, podemos dizer que a pesquisa do gene uidA pode ser considerada uma ótima ferramenta na triagem de isolados do sorotipo O157:H7. Por outro lado, o gene ehxA e a produção de Eh não se mostraram como bons marcadores para pesquisa de cepas Stx positivas. Houve uma ampla diversidade de sqrotipos/sorogrupos entre as cepas STEC típicas. É importante salientar que, neste estudo, STEC O157:H7 foi detectada pela primeira vez no Brasil em amostra de carcaça de bovino criado em confinamento. A detecção de cepas STEC em amostras de fezes e principalmente em amostras de carcaças de bovinos demonstra um potencial risco à saúde pública, uma vez que tais cepas podem contaminar e chegar viáveis ao produto final. / Shiga toxin (Stx)-producing Escherichia coli (STEC) are considered important foodborne pathogens that have the intestinal tract of ruminants, in particular cattle, as reservoir. These microorganisms are associated with severe human diseases as hemorrhagic colitis (HC) and hemolytic-uremic syndrome (HUS). The aims of this research were to evaluate the occurrence of STEC from different sources during the feedlot cattle breeding and slaughtering; detecting the presence of stx1, stx2, ehxA and eaeA genes; identifying O157:H7 strains through uidA; evidencing Stx and Eh production capacity; identifying stx and eaeA variants and determining STEC strains serotypes and genetic diversity. The potentially pathogenic strains were screened by detection of stx1, stx2, ehxA, eaeA and uidA, and Eh production, amongst 628 isolates studied. Fifty isolates were identified as STEC and 12 others as atypical EPEC. Among the STEC isolates, 76% were from feces, 18% from carcasses and 6% from water samples. Six strains isolated from feces and one from carcass were serotyped as O157:H7, ali being positive for the uidA. No other serogroup linked to outbreaks or sporadic cases of HC and HUS were found. From the 30 strains that showed cytotoxic effect on Vero cells, the great majority (96.7%) was positive for stx. Using an immunochromatographic assay, it was possible to identify the type of Stx produced by 17 out of the 50 STEC strains. All but one of these strains harbored the gene correspondent to the identified toxin. The other strain, even though producing both toxins, presented only stx2. It was possible to determine by PFGE the dissemination and persistence of STEC strains among the animals. 14/50 (28%) STEC strains were positive for the variant Stx2d activatable. Amongst 21 eaeA-positive strains, the variants of this gene were detected only in eight, being seven positive for eae-γ and the other eae-β. The results showed that uidA gene can be considered an excellent tool for screening O157:H7 strains. On the other hand, ehxA and Eh production, could not be considered as good markers for Stx-positive strains detection. A great diversity of serotypes/serogroups was observed among typical STEC strains. It is important to notice that this is the first report of O157:H7 strains in carcasses trom feedlot cattle in Brazil. The detection of STEC strain in fecal samples and in carcasses trom feedlot cattle evidences the potential public health risk, once these strains can contaminate the final product.
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