In vitro gut models provide several advantages over in vivo models for the study of the human gut microbiota. However, because communities developed in these models are simplified simulations of the in vivo environment it is necessary to characterize the reproducibility, repeatability and stability of cultured communities. We also need to broadly define the differences between in vitro consortia and the communities from which they are derived. In this study we characterized and validated a twin-vessel (independent, identical) single-stage chemostat model of the human distal gut. Samples were analyzed using a molecular fingerprinting technique (Denaturing Gradient Gel Electrophoresis) to compare and monitor changes in the overall structure of the communities while a phylogenetic microarray (Human Intestinal Tract Chip) was used to obtain phylogenetic information. We found that twin-vessels inoculated with feces developed and maintained diverse communities that reached stable compositions by at most 36 days post-inoculation. Communities were enriched in Bacteroidetes but not Clostridium cluster XIVa, Bacilli or other Firmicutes relative to the fecal inocula. Vessels were very reproducible when inoculated with identical fecal inocula, less similar when inoculated with consecutive fecal donations from the same donor, and maintained donor-specific identities when inoculated with feces from different donors. Norepinephrine exposure (undefined perturbation) did not appear to have a substantial effect on the structure of chemostat communities, while clindamycin treatment (defined perturbation) caused large changes in the structure of chemostat communities. Packed-column biofilm reactors incorporated a simulated mucosal environment into our chemostat system, allowing us to simultaneously culture biologically relevant planktonic and biofilm communities that were complex, reproducible, and distinct. Defined communities were comparable to fecal communities at the phylum/class-level but established stable compositions more rapidly. While it was difficult to assess the persistence of synthetic stool in a healthy fecal chemostat community (+/- antibiotic perturbation), mixing communities from two donors resulted in a mixed community that more closely resembled one donor over the other. Although future experimentation is required, the results presented here show our twin-vessel single-stage chemostat model represents a valid simulation of the human distal gut environment and can support complex, representative microbial communities ideal for experimental manipulation. / Canadian Institutes of Health Research; Ontario Ministry of Agriculture, Food and Rural Affairs; Ontario Ministry of Research and Innovation; Canada Foundation for Innovation; Ontario Ministry of Training, Colleges and Universities

Two different feeding trials were conducted to evaluate the effects of dietary supplementation with the dairy/yeast prebiotic GroBiotic-A (GBA) to Nile tilapia diets. A nutritionally complete basal diet was supplemented with GBA at either 1 or 2% of dry weight, and all three diets were fed to triplicate groups of juvenile fish in two consecutive trials. Trial 1 continued for 8 weeks, while Trial 2 was conducted for 5 weeks to more specifically assess immunological responses, intestinal characteristics and disease resistance of tilapia. At the conclusion of Trial 1, there were no differences in weight gain (WG) or feed efficiency (FE) among fish fed the three diets. However, fish fed the diet with GBA at 2% had significantly increased survival and noticeably elevated levels of plasma lysozyme compared to fish fed the basal diet or the diet with GBA at 1%. Similarly, at the conclusion of Trial 2, WG and FE were unaffected by GBA supplementation; however, fish fed the diet with GBA at 2% also exhibited elevated plasma lysozyme as well as significantly (P < 0.05) increased levels of extracellular superoxide anion production (EX-SOAP) by macrophages. Dendrogram analysis of denaturing gradient gel electrophoresis (DGGE) images detected a significantly different microbial community within the intestine of fish fed the diet with GBA at 2% compared to fish fed the basal diet and diet with GBA at 1%. None of the experimental diets resulted in significant improvements to survival after exposure to Streptococcus iniae due to within treatment variability. However, fish fed the diet with GBA at 2% did tend to experience reduced mortality (12.5%) as compared to fish fed the basal diet (35%). Thus, supplementation of GBA at 2% of diet did alter the gut microbiota of tilapia and enhanced immunological responses and disease resistance to S. iniae.

The effect of intestinal microbiota and dietary supplementation of mannan oligosaccharides (MOS) on mucosal architecture and digestive physiology in broiler chicks was examined. In experiment 1, pre-sterilized eggs (Ross x Ross 308) were placed in three HEPA (high efficiency particulate air)-filtered isolator units at day 19 of incubation. Germ-free chicks in one isolator were conventionalized by exposure to cecal contents from a laying hen. Bacterial contamination occurred in one germ-free isolator such that these birds were monoassociated by a bacterium within the Acinetobacter spp. resulting in 3 categories of microbial status including germ-free (GF, n=10), conventionalized (CV, n=19) and monoassociated (Mono, n=13) birds. Dietary treatments assigned to each isolator consisted of a negative control (NC, 0 g/kg of MOS in the basal diet) and MOS (2 g/kg of MOS in the diet) resulting in a 2X3 factorial treatment arrangement. At 7 d of age, body weight was recorded and birds were killed to permit collection of visceral organs, intestinal tissues and cecal contents. Body weight, relative length of small intestinal segments and relative bursa weight were significantly increased in CV birds. These birds also had increased crypt depth and lamina propria area. Dietary MOS increased villus height and villus surface area in CV birds compared with GF and Mono birds. Transcripts for all housekeeping genes tested in ileal tissue were increased by MOS such that transcripts were normalized to unit mass of total RNA. In comparison to birds fed the NC diet, MOS significantly increased the abundance of proliferative cell nuclear antigen (PCNA), toll-like receptor (TLR)-4, avian β-defensin (GAL)-6, interleukin (IL)-8, peptide transporter 1 (PepT1) and sodium-dependent glucose transporter (SGLT)-1 transcripts in ileum per unit total RNA. However, the effect of microbial status on selected gene expression profiles was surprisingly limited. A second experiment was conducted to confirm the conventionalization protocol produced a complex microbiota similar to conventionally reared birds. Twenty day-old broiler chicks (Ross x Ross 308) were assigned to one of two wire-floored battery cages provided the NC and MOS diets ad libitum and killed at 7 d of age. Terminal restriction fragment length polymorphism (TRFLP) analysis demonstrated that microbial diversity indices (Richness, Evenness, Shannon, and Simpson) were greater in conventionalized gnotobiotic birds compared to the conventionally reared birds confirming a successful conventionalization strategy in the gnotobiotic trial. These studies demonstrate that under good hygienic conditions, CV chicks thrive similar to GF animals. Based on responses to MOS observed in GF birds, evidence indicates that MOS, independent of changes in microbial composition, directly modifies host response parameters including innate immune activation, digestive and absorptive function.

Les oomycètes phytopathogènes ont co-évolué avec les microbiotes des plantes hôtes. Il en résulte la formation de biofilms et des réseaux complexes d’interactions dont nous commençons juste à comprendre l’incidence sur la biologie et la virulence des oomycètes. Déterminer la nature de ces interactions et leur rôle dans le contexte d’une infection est aujourd’hui un enjeu cognitif qui concerne la caractérisation des mécanismes moléculaires et communautaires sous-jacents. C’est également une opportunité en termes d’innovation pour élaborer des méthodes de lutte alternative à l’usage de fongicides. Dans ce contexte, ce travail de thèse a consisté à étudier, d’une part, la formation de biofilm chez Phytophthora parasitica, un oomycète polyphage et tellurique, ainsi que, d’autre part, les interactions au sein de ce biofilm entre P. parasitica et le microbiote procaryote rhizosphérique de la plante hôte Solanum lycopersicum. L’analyse du génome de P. parasitica et du transcriptome du biofilm a conduit à la caractérisation d’une nouvelle famille de mucines restreinte à la lignée des oomycètes, les protéines MUCL. Ces 315 protéines sécrétées (25-30 kDa) sont réparties en 15 groupes et possèdent deux domaines : un domaine hautement conservé de fonction inconnue ; un domaine caractéristique des mucines, riche en résidus Sérine et Thréonine avec de très nombreux sites putatifs d’O-glycosylation. Chez P. parasitica, les 3 gènes PPMUCL1/2/3 sont exprimés et co-régulés spécifiquement au stade biofilm. / The interactions between a pathogen and the host surface resident microbiota are critical to disease outbreak. These interactions shape the distribution, the density and the genetic diversity of inoculum. However for most plant pathogens how each of these interactions acts on disease as a single one or as a member of a functional network remains to be specified. This issue is addressed here through the analysis of two types of interactions involving the polyphagous oomycete P.parasitica : (i) the intraspecific interaction that leads to monospecific biofilm formation by P. parasitica zoospores on plant surface; (ii) the interspecific interactions that occur between P. parasitica biofilm and the prokaryotic microbiota of Solanum lycopersicum rhizosphere. The biology of monospecific biofilm is investigated through the characterization of MUCL, a new oomycete-specific Mucin-like Protein family. Gene profiling, biochemical and immunohistological analyses define the extent of this family and lead to identify three members, PPMUCL1/2/3, as residing in P. parasitica biofilm. The Phytophthora parasitica-Microbiota interaction is explored using first a metagenomic approach. Two microbial metagenomes derived from a soil of a tomato greenhouse is defined and compared after 16S RNA gene sequencing: M1 which corresponds to the sub-rhizospheric microbiota able to colonize the roots of axenic tomato seedlings; M2, the sub-microbiota able to colonize the tomato seedling roots previously coated with P. parasitica monospecific biofilm. A representative collection of microorganisms from M2 were also obtained through in vitro selection on a medium prepared from P. parasitica extract.

Orientador: Katia Sivieri / Banca: Fernanda Lopes Kinouchi / Banca: Thais Borges Cesar / Resumo: Introdução: A microbiota intestinal se mantem em equilíbrio (homeostase) durante a fase adulta do ser humano, porém pode se desestabilizar através do estresse, tratamentos quimioterápicos, medicamentos e dietas. A homeostase pode ser alcançada através da ingestão de probióticos, prebióticos e componentes bioativos, tais como os flavonóides cítricos do tipo hesperitina e naringina. Objetivo: Avaliar o efeito da ingestão crônica de suco de laranja pasteurizado (POJ) sobre a microbiota intestinal das mulheres adultas. Material e métodos: foram avaliadas dez mulheres adultas, que ingeriram suco de laranja pasteurizado durante 60 dias, com um período de esmaecimento de 30 dias. As fezes foram coletadas antes da ingestão de suco de laranja (basal) e depois a cada 30 dias até o final do experimento, totalizando 120 dias do período experimental. Durante todo o período experimental, foi realizada a avaliação antropométrica de todos os indivíduos que participaram no estudo. Para a avaliação da microbiota intestinal, foram realizados análises microbiológicas dependente de cultivo usando meios seletivos para bactérias anaeróbias totais, Lactobacillus spp., Bifidobacterium spp. e Clostridium spp. Uma avaliação independente de cultura foi realizada usando a desnaturação Gradient Gel Electrophoresis (DGGE). Para a avaliação dos metabolismos microbiano foram realizadas as análises de pH, amónio (NH4 +) e ácidos graxos de cadeia curta (AGCC).Resultados: A ingestão crônica de suco de laranja n... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Introduction: The gut microbiota remains balanced (homeostasis) during the adult stage of the human being, but can be destabilized through stress, chemotherapeutic treatments, medicines and diets. Homeostasis can be achieved through ingestion of probiotic, prebiotic, and bioactive components such as hesperitin and naringin-type citrus flavonoids. Objective: To evaluate the effect of chronic ingestion of pasteurized orange juice (POJ) on the intestinal microbiota of adult women. Material and Methods: Ten adult women were evaluated, which ingested pasteurized orange juice during 60 days, with a washout period of 30 days. The stool was collected before orange juice intake (basal) and then every 30 days until the end of the experiment, totaling 120 days of experimental period. Throughout the experimental period, the anthropometric evaluation of all individuals who participated in the study was performed. For the evaluation of the intestinal microbiota, plate count analyzes were performed using selective media for total anaerobic bacteria, Lactobacillus spp., Bifidobacterium spp., and Clostridium spp. An independent culture evaluation was performed using Denaturing Gradient Gel Electrophoresis (DGGE). The pH, ammonium (NH4 +) and short chain fatty acids (SCFA) were evaluated for microbial metabolism. Results: Chronic intake of orange juice did not influence the body composition measurements but improved blood biochemical parameters. POJ showed positive modulations of the microbiota composition and metabolic activity. In particular, numbers of faecal Bifidobacterium spp and Lactobacillus spp were higher after 60 days of POJ intake. PCR-DGGE analysis showed that the microbiota of all the individuals studied had a similar composition in relation to total bacteria. In relation to the microbial metabolism, it was observed reduction of NH4+ values and increase (p≤0.05) in the production... (Complete abstract click electronic access below) / Mestre

Les bactéries du phylum Bacteroidetes, classe Bacteroidia, sont parmi les plus importantes dans microbiotes gastrointestinaux des humains et d'autres mammifères. La bouche, entrée du tube digestif, est un environnement avec des sites anatomiques variés, auxquels s'associent des microbiotes de composition différente. L'union de la gencive et des dents, le sillon gingivo-dentaire ou sulcus, est un site de dépôt d'un biofilm complexe appelé plaque dentaire. Une bactérie de ce phylum, Porphyromonas gingivalis, est capable de perturber le système immunitaire humain et de produire un déséquilibre du biofilm oral également nommée dysbiose. Ceci déclenche la formation de la poche parodontale, un creusement pathologique du sulcus, et l'apparition de la parodontite. D’autres espèces du genre Porphyromonas sont également associées à la parodontite notamment chez les canidés. Les populations de P. gingivalis sont panmictiques et la plasticité de leurs génomes importante. La bioinformatique peut aider à identifier les causes de la mosaïcité des génomes de cette bactérie, à étudier les facteurs de virulence au niveau du genre bactérien pour expliquer l'existence d'espèces pathogènes et d'autres commensales et à décrire la dysbiose liée à la parodontite. La génomique comparative de P. gingivalis a démontré une corrélation entre le nombre de contigs dans les génomes draft de cette espèce et les répétitions génomiques, notamment des séquences d'insertion. Nous avons re-séquencé, re-assemblé et re-annoté trois souches de référence de cette bactérie qui avaient des génomes complets, en utilisant un séquençage en long-read. Nous avons mis en évidence des erreurs d'assemblage sur les trois génomes publiés, que nous avons corrigé. Une étude du pangénome de ces trois souches montre un génome core important. La plasticité de l'espèce serait donc plus dans l'organisation du génome que dans les différentes capacités de codage. Une sous partie du génome core, dont les gènes ont un pourcentage d'identité nucléotidique plus faible que la plupart (génome core variant) est intéressante pour expliquer les différences phénotypiques de ces bactéries. Nous avons étudié la répartition d'un facteur de virulence, les fimbriae, structures d'adhésion, au sein du genre Porphyromonas et lié les loci à la phylogénie et au caractère pathogène des espèces. Finalement, une description de la dysbiose qui a lieu lors d'une parodontite est faite par une analyse du microbiote de patients atteints de parodontite et d'individus sains. Les genres prépondérants lors des deux états sont mis en évidence. Au cours de ces travaux, nous montrons l'importance de la biocuration et sa valeur ajoutée dans les travaux de génomique et bioinformatique en général. Seulement en faisant ce travail lent et lourd de biocuration, les réponses apportées aux questions biologiques seront pertinentes. / Bacteria of Bacteroidetes phylum, Bacteroidia class, are amongst the more important in gastrointestimal microbiota, either human or from other mammals. The mouth, digestive tube entry, is an environment with varied anatomic sites, each having a particular microbiota with different composition. The union between gingiva and teeth, the gingival sulcus, is a site for biofilm (dental plaque) formation and accumulation. Porphyromonas gingivalis, a bacterium from this phylum, can modulate the inmune system and produce an oral biofilm desequilibrium called dysbiosis. This triggers the formation of a periodontal pocket, a pathological deepening of the gingival sulcus, and the emergence of periodontitis. Other Porphyromonas species are also associated to periodontitis, mainly in canids. P. gingivalis populations are panmictic and their genomes are highly plastic. Bioinformatics can help to identify the causes of this genomic mosaicity, to study Porphyromonas virulence factors in order to explain why some species are pathogens and other are commensal, and to describe the dysbiosis linked to periodontitis. P. gingivalis comparative genomics showed a correlation between the number of contigs in draft genomes and genomic repeats, mainly insertion sequences. We resequenced, reassembled and reannotated three reference strains of this bacterium that already had complete published genomes, using long-read sequencing. We showed that misassemblies were present in the three published genomes, and we corrected them. A pangenome study of the three strains showed that the core genome is preponderant. The species plasticity might be related more to the genome organization than to different coding capacities. A subpart of th core genome, with genes having a nucleotidic identity percentage lower than the majority (variable core genome), is interesting for explaining the phenotypic differences of bacteria. We analysed the repertoire of a virulence factor, fimbriae, adhesion structures, in the Porphyromonas genus to link the loci to phylogeny and pathogenicity of its species. Finally, we described the dysbiosis occuring with periodontitis, analysing gingival microbiota of patients having the illness and healthy individuals. Preponderant genera in both states are highlighted. With this work, we demonstrate the importance of biocuration and its added value for genomic and bioinformatic studies in general. Only with this slow and arduous work, the answers to biological questions will be relevant.

The weaning transition period in pigs is linked to increased vulnerability to enteric disorders, which is partly attributed to destabilisation of the gut microbiota. Post-weaning colibacillosis is an economically important disease of the small intestine, which is most commonly caused by enterotoxigenic Escherichia coli (ETEC) strains. This disease has been variably linked to a diarrhoeal phenotype and decreased growth rate under clinical or sub-clinical conditions, and has been associated with shifts in particular bacterial populations using culturing methods. The emergence of next-generation sequencing technologies such as 16S rRNA gene metabarcoding now allows higher resolution study of complex microbial communities, without being reliant on the ability to culture fastidious micro-organisms. As part of this project, a 16S rRNA gene metabarcoding method was developed and validated to allow qualitative and quantitative measurement of gut microbiota shifts. A series of experimental ETEC challenge trials were carried out to monitor temporal faecal microbiota dynamics (Chapter 2), to further understand ETEC adhesion and shedding dynamics (Chapter 3) and to study potential changes in both ileal and faecal microbiota populations in response to dietary protein manipulation (Chapter 4). The effects of experimental treatments on pig health and performance were also measured as part of each experiment. Temporal shifts in ileal and faecal microbiota structure and stability were observed over the post-weaning period, as well as shifts in relative abundances of particular bacterial phylotypes (P < 0.05) (Chapter’s 2 and 4). ETEC challenge had no effects on faecal microbiota composition, pig health and performance when comparing to samples obtained from sham-challenged pigs (P > 0.05). However, when taking ETEC shedding level into account, variations in both microbiota structure and stability were observed at specific time points (P < 0.05) (Chapter 2). After a single-dose ETEC challenge, ETEC adhesion in the ileum and faecal shedding were evident up to 4 and 6 days post-challenge, respectively (Chapter 3). Changes in ileal microbiota structure and stability were observed in response to ETEC challenge (P < 0.05), with no changes exerted at faecal level (P > 0.05). Additionally, different dietary protein levels were linked to changes in ileal microbiota structure, stability and phylotype relative abundances (P < 0.05). Interestingly, significant differences in ileal microbiota structure were evident in samples obtained from ETEC-challenged pigs fed the low and high protein diets, with the pigs fed the high protein diet having significantly less stable ileal communities at population level (P < 0.05) (Chapter 4). The treatments had no effect on host performance (P > 0.05), but faecal consistency scores were higher in pigs fed the high protein diet (P < 0.05). In conclusion, both ETEC challenge and manipulation of dietary protein level had profound effects on ileal microbiota composition and faecal microbial communities were variable according to ETEC shedding status. These findings have implications for the development of alternative management strategies for enteric diseases in weaner pigs.

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Agrárias, Programa de Pós-Graduação em Aquicultura, Florianópolis, 2011 / Made available in DSpace on 2012-10-25T21:28:12Z (GMT). No. of bitstreams: 1 293184.pdf: 307065 bytes, checksum: 9c2d3ee7559641fd0ec3c33b9550d9b4 (MD5) / A microbiota intestinal de jundiá Rhamdia quelen e tilápia Oreochromis niloticus foi comparada. Foram observadas bactérias capazes de digerir os macro nutrientes (proteína, lipídios e carboidratos) presentes nas dietas, estando, em geral, em maiores números na tilápia. A distribuição de grupos bacterianos variou ao longo do trato intestinal, sendo diferente entre as espécies estudadas. O jundiá apresentou maior crescimento de bactérias proteolíticas e lipolíticas na porção posterior, onde também ambas espécies tinham mais bactérias amilolíticas. Pode haver maior degradação de amido por enzimas exógenas provenientes da microbiota na porção final do intestino, o que aumentaria a disponibilidade deste nutriente para o hospedeiro. Comparou-se também a microbiota intestinal entre as duas espécies, após a administração de dietas contendo milho, trigo, mandioca, arroz ou dextrina. Os jundiás alimentados com dieta contendo arroz apresentaram mais bactérias totais. Por outro lado, quando mandioca ou milho foi utilizado, bactérias amilolíticas foram mais presentes em tilápia. A microbiota da parede intestinal dos peixes foi sensível a dieta administrada, que alterou sua composição. Fusobacterium foi detectada em jundiás alimentados com dietas contendo arroz, e contendo mandioca, dextrina, arroz e milho para tilápia. Foi evidenciada diferenciação da microbiota de jundiá e tilápia, já que foram observadas apenas no primeiro, bactérias do grupo das Spirochaetales, comuns nos tratamentos com milho, mandioca e dextrina. Estudos adicionais são necessários para melhor compreensão da microbiota intestinal na digestão de carboidratos em peixes, associando-se técnicas bacteriológicas convencionais com moleculares.

Orientador: Daniela Cardoso Umbelino Cavallini / Banca: Raquel Bedani / Banca: Kátia Sivieri / Resumo: As doenças inflamatórias intestinais (DII), entre elas a doença de Crohn (DC) e a retocolite ulcerativa idiopática (RCUI) compreendem um grupo de patologias que possuem como principal característica a inflamação da mucosa intestinal. Embora sua origem ainda não seja completamente conhecida, existe uma crescente evidência baseada em estudos recentes associando predisposição genética, composição da microbiota intestinal e sistema imunológico como fatores precursores para a iniciação e progressão dessas patologias. O uso de determinadas cepas probióticas vem sendo apontado como uma forma promissora de se reduzir o risco de doenças inflamatórias intestinais, mais precisamente da colite ulcerativa. Diversos mecanismos têm sido propostos para explicar os benefícios dos probióticos, indicando que algumas cepas bacterianas são capazes de modular positivamente a microbiota intestinal e o sistema imune, além de produzirem metabólitos com capacidade antiinflamatória. Como os efeitos e os mecanismos de ação envolvidos são cepa-específicos, é de extrema importância a realização de novos estudos para compreender as interações entre microbiota intestinal e hospedeiro, contribuindo para o entendimento do potencial terapêutico dos probióticos nas doenças relacionadas ao desequilíbrio da microbiota intestinal. O presente trabalho se propõe a investigar o efeito da ingestão diária de um produto à base de extrato aquoso de soja, fermentado com Enterococcus faecium CRL 183 e Lactobacillus helveticus 416 e com adição de Bifidobacterium longum ATCC 15707, na colite induzida quimicamente em ratos. A colite foi induzida, pela administração de dextran sulfato de sódio (DSS) a 4%, que foi dissolvido na água fornecida diariamente aos animais e administrado durante um período de sete dias. Os animais foram distribuídos aleatoriamente em cinco grupos (n=10): Grupo C: Animais sadios que não receberam os produtos em estudo. ... / Abstract: Inflammatory bowel disease (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), comprise a group of disorders and their main characteristic is an inflammation of the intestinal mucosa. Although its origin is not yet fully known, there is growing evidence linking genetics predisposition, composition of the intestinal microbiota and immune system factors as precursors for the initiation and progression of these pathologies. The use of certain probiotic microorganisms has been considered as promising way to reduce the risk of inflammatory bowel disease, specifically ulcerative colitis. Several mechanisms have been proposed to explain the benefits of probiotics, indicating that some bacterial strains are able to positively modulate the intestinal microbiota and the immune system, and produce metabolites with anti-inflammatory capacity. As the effects and the mechanisms involved are strain-specific, further studies are extremely important to understand the interactions between gut microbiota and host, contributing to the knowledge on therapeutic potential of probiotics in diseases related to dysbiosis. This current paper aims to bring together the various results and information based on scientific evidence that are related to probiotics and the inflammatory bowel disease, with emphasis on the possible mechanisms involved in this action. Furthermore, the effects of daily ingestion of a product based on an aqueous extract of soybean, fermented by Enterococcus faecium CRL 183 and Lactobacillus helveticus 416 with the addition of Bifidobacterium longum ATCC 15707, were also investigated on chemically induced colitis in rats. Colitis was induced by 4% dextran sulfate sodium (DSS), dissolved in the drinking water supplied to the animal, which was ingested daily for a period of seven days. The animals will then be assigned randomly to four groups (n=10): Group C: healthy animals that do not receive the products under study; Group CL: ... / Mestre

Orientador: José Moacir Marin / Banca: Everlon Cid Rigobelo / Banca: Davi Rodrigo Rossato / Banca: Patrícia Amoroso de Andrade / Banca: Caroline Peters Pigatto de Nardi / Resumo: Escherichia coli de sorogrupo não- O157 produtora de Shiga toxina é reconhecida como causadora de sérias doenças em seres humanos. Entretanto, as pesquisas relacionadas à persistência das STEC não- O157 em solos agricultáveis são bastante limitadas. No presente estudo foi analisada a sobrevivência de E.coli genérica, E.coli portadora do gene eae e STEC não- O157 portadoras do gene stx1, stx2 e eae em dois solos agricultáveis, cultura de cana-de-açúcar e pastagem em duas situações diferentes, solos esterilizados por autoclavação e solo não autoclavado. As linhagens de E.coli foram inoculadas nos dois solos em ambas as situações em um sistema de microcosmo, o qual foi avaliado por 60 dias. Os resultados mostraram que todas as linhagens de E.coli foram recuperadas em menor número nos solos não autoclavados do que nos solos esterilizados por autoclavação. Também foi verificado que as linhagens STEC não- O157 sobreviveram por um período maior do que a linhagem de E.coli genérica no solo sob pastagem não autoclavado, no mínimo por 60 dias. Nós devemos prestar mais atenção ao longo período de sobrevivência das linhagens STEC não- O157 em solos de pastagem devido ao seu alto potencial de risco ao meio ambiente / Abstract: Shiga toxin producing Escherichia coli non- O157 serogroup has been recognized as cause of serious diseases in human. However, research on the persistence of STEC non- O157 in preharvest is limited. In the current study we analysed the survival behavior of generic E.coli, E.coli carrying eae gene and STEC non- O157 strain carrying stx1, stx2 and eae gene in two agricultural soils, sugar cane culture and grassland in two different situations autoclaved soil and non- autoclaved soil. The E.coli strains were inoculated in both soils in a microcosm system which was analysed for sixty days. Results showed that all E.coli strains were recovered in a smoller number in non- autoclaved soils than in the autoclaved soils. Also was verified that the STEC non- O157 strains survived longer than the generic E.coli strain in the non autoclaved grassland soil, at least for sixty days. We should pay more attention to the STEC non- O157 serogroup long survival in grassland soil and its potential environmental risk / Doutor