Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2016-01-21T11:19:26Z No. of bitstreams: 2 Dissertação - Sarah Inês Rodrigues Rosa - 2015.pdf: 3749246 bytes, checksum: 1a9a8f107442eeddf5e57f4eaaf4e954 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2016-01-21T11:22:28Z (GMT) No. of bitstreams: 2 Dissertação - Sarah Inês Rodrigues Rosa - 2015.pdf: 3749246 bytes, checksum: 1a9a8f107442eeddf5e57f4eaaf4e954 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2016-01-21T11:22:28Z (GMT). No. of bitstreams: 2 Dissertação - Sarah Inês Rodrigues Rosa - 2015.pdf: 3749246 bytes, checksum: 1a9a8f107442eeddf5e57f4eaaf4e954 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2015-03-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Campylobacteriosis have been related as main cause of gastroenteric diseases in Europe and North America. In Brazil, the lack of data about this disease hinders a comparison with other countries and difficult the decision making to combat the causative bacterium. Due high incidence of Campylobacter spp. in meat, main in poultry carcasses and by-products, this study aimed isolate and identify this bacteria in chicken fresh sausage sampled in Aparecida de Goiânia, in Goiás state. Thirty-four samples were collected in the period from July to October, each one were subdivided in 68 sub-samples, half of sub-samples were analyzed immediately, in fresh/chilled condition, and the other half were frozen for further analysis. In 11.65% of fresh samples were isolated Campylobacter coli and Campylobacter lari. For the frozen samples, no positive results were observed. Worked also with simple and double concentration of enrichment medium, recovering three positive samples in the simple one and a positive sample in the double. It was observed 100% resistance against the antimicrobial bases tested. It is recommended more studies of this nature, broadening the scope as to poultry products and greater number of samples; therefore, it is believed that they may evaluated the prevalence of this important microorganism in animal products in the Goiás state. Such investigations may provide important information for the National Program for Monitoring Prevalence and Bacterial Resistance in Chicken, established in 2008 by the National Agency of Sanitary Surveillance of the Ministry of Health. / Campilobacteriose tem sido frequentemente relatada como principal causadora de doenças gastroentéricas na Europa e América do Norte. No Brasil, a escassez de dados em relação à notificação dessa enfermidade dificulta uma comparação com outros países e a tomada de decisões quanto a políticas de combate à bactéria causadora. Devido a relatos de alta incidência de Campylobacter spp. em carnes, principalmente em carcaças de frango e derivados, este estudo teve como objetivo o isolamento e identificação dessa bactéria em linguiças de frango do tipo frescal obtidas no município de Aparecida de Goiânia, no estado de Goiás. Foram coletadas 34 amostras do produto no período de julho a outubro de 2014, cada uma delas foi dividida em duas partes totalizado 68 subamostras, metade delas foram imediatamente analisadas, na condição fresca/refrigerada, e metade foi submetida ao congelamento para posterior análise. Em 11,75% das amostras frescas pesquisadas, isolou-se Campylobacter coli e Campylobacter lari. Não foi observado resultado positivo para Campylobacter spp. nas linguiças congeladas. Trabalhou-se também, com simples e dupla concentração do meio de enriquecimento, recuperando três amostras positivas no meio simples e uma amostra positiva no meio em dupla concentração. Foi observada 100% de resistência frente às bases antibióticas testadas. Recomenda-se mais estudos desta natureza, ampliando a abrangência quanto aos produtos avícolas e com maior número de amostras, pois acredita-se que poderão avaliar a prevalência deste importante micro-organismo em produtos de origem animal no estado de Goiás. Tais investigações poderão contribuir com informações importantes para o Programa Nacional de Monitoramento da Prevalência e da Resistência Bacteriana em Frango, estabelecido em 2008 pela Agência Nacional de Vigilância Sanitária do Ministério da Saúde.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Campylobacter jejuni e Campylobacter coli sÃo importantes agentes etiolÃgicos de doenÃa diarrÃica na populaÃÃo mundial. A infecÃÃo por Campylobacter sp. à usualmente identificada por cultivo microbiolÃgico que leva aproximadamente 72 horas para identificaÃÃo do gÃnero. Nosso objetivo principal foi pesquisar a prevalÃncia de C. jejuni e C. coli em populaÃÃo infantil, com idade entre 2-36 meses, da Ãrea urbana de Fortaleza/CE, Brasil, em estudo do tipo epidemiolÃgico observacional caso-controle, utilizando, como ferramenta de detecÃÃo, a reaÃÃo em cadeia da polimerase (PCR). Outros objetivos consistiram em: investigar o impacto nutricional da infecÃÃo (casos) ou da colonizaÃÃo (controles) por Campylobacter sp.; determinar a presenÃa de trÃs genes de virulÃncia para a toxina citoletal distensora (CDT) de C. jejuni e avaliar a ocorrÃncia de inflamaÃÃo intestinal nas infecÃÃes causadas por Campylobacter sp. A populaÃÃo estudada consistiu de 83 casos e 83 controles, sendo os casos, crianÃas com histÃrico de diarrÃia nos 14 dias pregressos à seleÃÃo para o estudo. Foram avaliados parÃmetros sÃcio-econÃmicos atravÃs de questionÃrio epidemiolÃgico. Medidas antropomÃtricas foram coletadas para determinaÃÃo de escores-z no intuito de avaliar o perfil nutricional das crianÃas. A detecÃÃo de Campylobacter nas amostras congeladas foi realizada por ensaio imuno-enzimÃtico (ELISA) e PCR. Pela PCR tambÃm investigamos a presenÃa dos genes cdtA, cdtB e cdtC da CDT de C. jejuni. A avaliaÃÃo da inflamaÃÃo intestinal foi realizada pela pesquisa de lactoferrina fecal (LFF), atravÃs de ELISA semiquantitativa. Foi detectado, por PCR, C. jejuni em 9,6% dos casos (8/83) e 7,2% dos controles (6/83). C. coli foi detectado em 6,0% dos casos (5/83) e 1,2% dos controles (1/83). Os genes cdtA, cdtB e cdtC foram encontrados em 50% das amostras hipO+ (7/14). Houve diferenÃa significativa (p<0,05) dos escores WAZ e WHZ entre casos e controles portadores de C. jejuni, sendo que casos portadores apresentaram mÃdia inferior de WAZ e WHZ, quando comparados com os controles portadores. No grupo Casos, os portadores de C. jejuni apresentavam valor mÃdio de WHZ inferior ao valor mÃdio apresentado pelos casos nÃo-portadores. Mais de 80,0% das crianÃas estudadas apresentaram inflamaÃÃo intestinal caracterizada por elevados nÃveis de LFF, independente da presenÃa de diarrÃia e Campylobacter sp. Em conclusÃo, nossos achados corroboram dados da literatura cientÃfica relacionados à prevalÃncia de C. jejuni e C. coli na populaÃÃo infantil, existÃncia de portadores assintomÃticos e associaÃÃo entre a detecÃÃo do microorganismo e desnutriÃÃo. AlÃm disso, nossos dados apontam para ocorrÃncia de variabilidade genÃtica dentre as cepas de C. jejuni detectadas na populaÃÃo estudada em relaÃÃo à presenÃa ou ausÃncia dos genes de CDT. / Campylobacter jejuni and Campylobacter coli are important etiologic agents of worldwide diarrheal disease. Campylobacter sp. infection is usually identified by a 72 hour microbiological culture that identifies the genus of the responsible organism. Our main goal was to investigate the prevalence of C. jejuni and C. coli in children, aged 2-36 months, from urban Fortaleza, CE, Brazil, in an observational epidemiological case-control study using, as a tool of detection, the polymerase chain reaction (PCR). Our other goals were to investigate the nutritional impact of infection (cases) or colonization (controls) for Campylobacter sp., to determine the presence of three virulence genes of C. jejuni cytolethal distending toxin (CDT), and to evaluate the occurrence of inflammation in intestinal infections caused by Campylobacter sp. The study population consisted of 83 cases and 83 controls, where the cases consisted of children with a history of diarrhea in the 14 days prior to selection for the study. We assessed socioeconomic parameters through an epidemiological questionnaire. Anthropometric measurements were collected to determine z-score parameters for assessing the nutritional status of the children. Detection of Campylobacter from frozen samples was performed by enzyme-linked immunosorbent assay (ELISA) and PCR. Also, using PCR technology, we investigated the presence of C. jejuni genes cdtA, cdtB and cdtC. Intestinal inflammation was assessed by semi-quantitative ELISA detection of fecal lactoferrin (LFF). PCR technology detected C. jejuni in 9.6% of the cases (8/83) and 7.2% of the controls (6/83), while C. coli was detected in 6.0% of the cases (5/83) and 1.2% of the controls (1/83). CDT genes were found in 50% of hipO+ samples (7/14). There was a significant difference (p <0.05) in the weight for age z-scores (WAZ) and the weight for height z-scores (WHZ) between case and control carriers of C. jejuni, where case carriers showed lower average WAZ and WHZ than control carriers. Moreover, in the case group, carriers of C. jejuni showed a lower WHZ average than that of non-carrier cases of C. jejuni. More than 80.0% of the children studied had intestinal inflammation characterized by high levels of LFF regardless of the presence of diarrhea and Campylobacter sp. In conclusion, our findings corroborate data in the scientific literature related to the prevalence of C. jejuni and C. coli in pediatric populations, the existence of asymptomatic carriers and an association between the detection of the microorganism and malnutrition. In addition, our data suggest a genetic variability among the strains of C. jejuni detected in the study population, related to presence o absence of CDT genes.

Submitted by Franciele Moreira (francielemoreyra@gmail.com) on 2017-10-10T15:52:13Z No. of bitstreams: 2 Dissertação - Julierme José de Oliveira - 2014.pdf: 1186561 bytes, checksum: ee682becf7a3d3796f34ba3239320262 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-10-11T10:53:29Z (GMT) No. of bitstreams: 2 Dissertação - Julierme José de Oliveira - 2014.pdf: 1186561 bytes, checksum: ee682becf7a3d3796f34ba3239320262 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-10-11T10:53:29Z (GMT). No. of bitstreams: 2 Dissertação - Julierme José de Oliveira - 2014.pdf: 1186561 bytes, checksum: ee682becf7a3d3796f34ba3239320262 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2014-02-26 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Thermophilic species of Campylobacter spp. are often cited as the most common etiologic agent in cases of foodborne illnesses in several countries. When ingested even in small quantities (400 to 500 cells) this organism, through the mechanisms of pathogenicity, the host develops infectious gastroenteritis known as campylobacteriosis. This disease is closely related to the intake and improper handling of contaminated food, especially poultry, and birds the main reservoir of the microorganism. Poor knowledge climbs the role of eggs in the transmission of campylobacteriosis, based on the annual consumption of the food matrix, research clarifying all variables involving this food are essential. This study aimed to verify the occurrence of Campylobacter spp., identify thermophilic species involved and assess the level of antimicrobial susceptibility of isolates from chicken carcasses and eggs obtained from commercial establishments in the city of Goiânia. A total of 100 chicken carcasses and 100 dozens of eggs were evaluated using enzyme- linked immunosorbent assay for screening miniVIDAS ® with subsequent bacterial isolation and identification of samples by biotyping . By means of the methods employed observed that Campylobacter spp. was identified in 7% (7 /100) of chicken carcasses in 1% (1/100 ) of samples of eggs, 100 % of these were confirmed as belonging to the bacterial genus . The species with the highest number of isolates were Campylobacter jejuni (50 %), followed by Campylobacter coli ( 25 % ) and Campylobacter lari ( 25 % ). For antimicrobial resistance results were that 100% of the isolates were resistant to erythromycin, as well as ciprofloxacin and tetracyclines. For ceftriaxone and nalidixic acid resistance values were 91.7 % resistant. Chloramphenicol was 50% of resistant isolates, showed 33.3% sensitivity and 16.7% intermediate resistance. It was also observed that 100% of the isolates showed multidrug profile. Through the results obtained it is concluded that thermophilic Campylobacter are present in chicken carcasses and marketed in Goiânia eggs, whose distribution becomes relevant from the point of view of exposure to consumers. Campylobacter jejuni was the most frequent species. The six districts surveyed had bacteria of the genus in at least one category. Isolates when screened for response to antimicrobial proved multiresistant, denoting the importance of research as a way to support the election of bases and principles for the antibiotic treatment prescribed treatments. Poultry foods surveyed in this study and considered positive for the pathogen constitute risk to the consumer. / As espécies termotolerantes de Campylobacter spp. são frequentemente apontadas como o agente etiológico mais comum nos casos de doenças veiculadas por alimentos em diversos países. Ao ser ingerido mesmo em pequenas quantidades (de 400 a 500 células), esse microrganismo, por meio dos mecanismos de patogenicidade, desenvolve gastroenterite infecciosa no hospedeiro, conhecida como campilobacteriose. Esta doença está intimamente relacionada à ingestão e manipulação incorreta de alimentos contaminados, especialmente carne de frango, sendo as aves o principal reservatório. Pouco se sabe sobre o papel desempenhado pelos ovos na transmissão de campilobacteriose, tendo como base o consumo anual dessa matriz alimentar, pesquisas que esclareçam todas as variáveis envolvendo esse alimento são de fundamental importância. Pelo exposto, este estudo teve como objetivo verificar a ocorrência de Campylobacter spp., identificar as espécies termotolerantes circulantes na cidade de Goiânia, vinculadas aos estabelecimentos comercializadores de alimentos, relacionados à alta densidade populacional, localizados em distritos comerciais e avaliar o nível de suscetibilidade a antimicrobianos dos isolados de carcaças de frango e ovos provenientes destes estabelecimentos. Um total de 100 carcaças de frango e 100 dúzias de ovos foram avaliados utilizando como triagem o ensaio imunoenzimatico miniVIDAS® com posterior isolamento bacteriano das amostras e identificação por meio da biotipificação. Por meio dos métodos empregados observou-se que Campylobacter termotolerantes foi identificada em 7% (7/100) das carcaças de frango e em 1% (1/100) das amostras de ovos. A espécie com maior número de isolados foi Campylobacter jejuni (50%), seguidos por Campylobacter coli (25%) e Campylobacter lari (25%). Para a resistência à antimicrobianos os resultados reportaram que 100% dos isolados são resistentes à eritromicina, assim como à ciprofloxacina e tetraciclina. Para ácido nalidixico e ceftriaxona, os valores de resistência foram da ordem de 91,7%. Cloranfenicol foi resistente em 50% dos isolados, apresentou sensibilidade a 33,3% e resistência intermediária a 16,7%. Observou-se ainda que 100% dos isolados apresentaram perfil de multirresistência. Pelos resultados obtidos conclui-se que Campylobacter termotolerantes estão presentes em carcaças de frango e ovos comercializados na cidade de Goiânia, cuja distribuição torna-se relevante do ponto de vista da exposição aos consumidores. Campylobacter jejuni foi a espécie mais frequente. Os seis distritos pesquisados apresentaram bactérias do gênero pelo menos em um estabelecimento. Os isolados quando pesquisados quanto a resposta a antimicrobianos mostraram-se multirresistentes, denotando a importância desta investigação como forma de respaldar a eleição de bases e princípios para a antibioticoterapia para tratamentos prescritos. Os alimentos avícolas pesquisados neste estudo e considerados positivos para o patógeno constituem risco ao consumidor.

Made available in DSpace on 2014-08-20T14:37:50Z (GMT). No. of bitstreams: 1 dissertacao_daiani_teixeira_da_silva.pdf: 375746 bytes, checksum: 539868549fb7e9d324125c3f8040cb19 (MD5) Previous issue date: 2012-07-12 / Campylobacter is a bacteria related to foodborne illnesses. It is one of the most common causes of diarrhea in humans in the world. It might cause Guillain-Barre syndrome, which attacks the cells of the peripheral nervous system causing muscle paralysis. Some strains of this bacterium can produce a cytolethal distending toxin (CDT), which can exacerbate diarrheal diseases. Birds are the main reservoir of this micro-organism, of which they are asymptomatic hosts. During the slaughter of broilers, contamination of meat and its products may occur. They are the main responsible for infections in humans. The objective of this study was to verify the presence of C. jejuni and C. coli in poultry meat, chicken and human feces and investigate the presence of cdtA, cdtB and cdtC genes in the isolates. A hundred chicken fecal samples, a hundred samples of retail poultry products and a hundred samples of human feces were collected. The poultry products were washed with Brucella broth and spread onto plates of Columbia agar. The feces samples were directly spread onto plates containing this medium. Confirmation of isolates and species identification were performed by PCR. PCR was also used to investigate the presence of cdt genes. Campylobacter was found in 61% of the chicken fecal samples, in 20% of the poultry products and in 3% of the human feces. C. jejuni was the predominant species and 93,5% of them exhibited the cdt genes. Despite the fact that the prevalence of Campylobacter found in human feces was low, the occurrence of Campylobacter in broilers and poultry products sold in southern Rio Grande do Sul was high. Besides, it has been observed that most of the isolates were highly likely to produce CDT. These results suggest there is a need for preventive measures in the production system and good manufacturing practices in the industry so as to minimize contamination of products and reduce the risk to consumers. / Campylobacter é uma bactéria relacionada a doenças transmitidas por alimentos. É uma das causas mais comuns de diarreia em humanos em todo o mundo. Raramente, pode causar a Síndrome de Guillain-Barré, que ataca as células do sistema nervoso periférico, causando paralisia muscular. Algumas cepas desta bactéria podem produzir uma toxina citoletal distensiva (CDT) capaz de agravar os quadros diarreicos. As aves são o principal reservatório do micro-organismo, do qual são portadoras assintomáticas. Durante o abate de frangos de corte pode ocorrer a contaminação da carne e seus produtos, que são os principais responsáveis pelas infecções em humanos. O objetivo do trabalho foi verificar a presença de C. jejuni e C. coli em carne de frango, fezes de frango e humanas e pesquisar a presença dos genes cdtA, cdtB e cdtC nos isolados. Foram coletadas 100 amostras de conteúdo fecal de aves de corte, 100 de produtos de frango no comércio varejista e 100 de fezes de humanos. Os produtos de frango foram lavados com Caldo Brucella e semeados em placas de Agar Columbia. As amostras de fezes foram diretamente semeadas nas placas com este meio. A confirmação dos isolados e a identificação das espécies foram realizadas através da técnica de PCR. Também foi utilizada a PCR para pesquisar a presença dos genes cdt. Obteve-se 61% de amostras de fezes de frango positivas para Campylobacter, 20% de produtos de frango e 3% de fezes de humanos. A espécie C.jejuni foi predominante e 93,5% dos isolados desta espécie apresentaram os genes para a toxina CDT. Apesar da prevalência de Campylobacter observada em fezes de humanos ter sido baixa, a ocorrência em fezes de frangos de corte e produtos de frango comercializados na região Sul do Rio Grande do Sul foi elevada e a maioria dos isolados apresentou potencial para a produção da toxina CDT. Esses resultados são indicativos da necessidade de medidas preventivas no sistema de produção e de boas práticas de fabricação na indústria, de forma a minimizar a contaminação dos produtos e diminuir o risco para os consumidores.

No description available.

Background : The sources and the epidemiology of Campylobacter jejuni (CJ) in environmental water are not well understood. We developed a spatial analysis methodology able to identify the main environmental factors predicting the presence and quantity of Campylobacter in river water. Methods : For two years, water samples were collected weekly and scanned for CJ and fecal coliforms at 32 sampling sites of Estrie hydrographic network, Québec. The quantity of CJ in water was estimated using the Most Probable Number method (MPN). The 32 sampling sites were linked to their catchment area; 10 of them were excluded from the analysis, because their hydrographic basin was not independent from the other sites. For each site, the following environmental variables were included: Water flow, slope, land-cover, land-use including type of farming, animal density, total precipitation in the 3 days prior to water sampling. A stepwise multivariate regression was realized across the different analysis windows to define the size of the area upstream from the sampling sites (from 1.5 to 24 km) which was the most closely associated with the mean quantity of CJ, and which environmental factors were associated with a higher mean quantity of CJ in water. Results : Preliminary results show that an area defined by a radius of 14 km upstream of the sample site was the most contributing zone for the bacteria (r2=0.38, p=0.002). Within this 14 km area, the only significant variable associated with a higher mean quantity of CJ was bovine density (p=0.002). When analyzing the data within a 120 m buffer zone across 14 km upstream of the sampling sites (r2=0.40, p=0.001), the only significant variable associated with a higher mean quantity of CJ was the percentage of agricultural surface (p=0.001). Conclusions : These results suggest a strong implication of bovine density in conjunction with crops and associated manure spreading on the quantity of CJ in environmental water.

Contexte: Les infections gastro-intestinales constituent un important problème de santé publique. Si plusieurs études recensent l'épidémiologie des cas sporadiques, peu se penchent sur la répétition d'infections dans certains ménages. L'objectif de cette étude est de déterminer quels sont les facteurs de risque associés à une récidive à Campylobacter ou à Salmonella déclarés de 2001 à 2007 dans les ménages en Montérégie. Méthodologie: Deux études ont été réalisées. Une étude descriptive a été conduite afin de dresser un portrait des deux groupes à l'étude soit : ménages avec répétitions d'infections à Campylobacter ou à Salmonella et ménages sans répétition d'infection (avec cas sporadique seulement). L'ensemble des sujets de cette étude ont été sélectionnés à partir du registre MADO. Une étude cas-témoins a ensuite permis de comparer les facteurs de risque pour chaque groupe de ménages. Un questionnaire administré au téléphone permettait de recueillir les habitudes des ménages-cas et des ménages-témoins. Les analyses ont été effectuées par régression logistique conditionnelle adaptée pour un appariement 1 cas : 2 témoins. Résultats: L'analyse descriptive portait sur 4181 cas d'infections à Campylobacter et Salmonella , déclarés du ler janvier 2001 au 31 décembre 2007. Le pourcentage de cas partageant la même adresse a été estimé à 7,8% pour Campylobacter et 7,6% pour Salmonella . Les cas de récidive présentent les mêmes caractéristiques que les cas sporadiques en ce qui concerne l'agent le plus en cause, la saison de survenue, l'âge du cas et le milieu d'habitation. Les habitudes des cas provenant de 80 ménages avec récidive et 160 ménages sans récidive ont été comparées. Dans un modèle final, en tenant compte seulement des variables affectant le ménage, il apparaît que l'habitation dans un milieu rural (RC = 2,89 ; IC95% = 1,53 - 5,46), la présence d'enfants de moins de 5 ans (RC = 2,63 ; IC95% = 1,29 - 5,37), l'exposition à une source hydrique contaminée (RC = 2,6 ; IC95% = 1,18 - 5,93) et le travail en contact avec des animaux (RC = 2.39 ; IC95% = 1,06 - 5,36) soient associés à un risque de récidive dans le ménage. Conclusion: Cette étude révèle que les répétitions de cas à certaines adresses peuvent s'expliquer par des caractéristiques du ménage. Des habitudes de vie spécifiques dans les ménages avec récidives par rapport aux ménages avec cas sporadiques ont été identifiées.

Dihydrodipicolinate Synthase (EC 4.3.3.7; DHDPS), the product of the dapA gene, is an enzyme that catalyzes the condensation of pyruvate and S-aspartate-β-semialdehyde (ASA) into dihydrodipicolinate via an unstable heterocyclic intermediate, (4S)-hydroxy-2,3,4,5-tetrahydro-(2S)-dipicolinic acid. DHDPS catalyzes the first committed step in the biosynthesis of ʟ-lysine and meso-diaminopimelate; each of which is a necessary cross-linking component between peptidoglycan heteropolysacharide chains of bacterial cell walls. Therefore, strong inhibition of DHDPS would result in disruption of meso-diaminopimelate and ʟ-lysine biosynthesis in bacteria leading to decreased bacterial growth and cell lysis. Much attention has been given to targeting the active site for inhibition; however DHDPS is subject to natural feedback inhibition by ʟ-lysine at an allosteric site. In DHDPS from Campylobacter jejuni ʟ-lysine is known to act as a partial uncompetitive inhibitor with respect to pyruvate and a partial mixed inhibitor with respect to ASA. Little is known about how the protein structure facilitates the natural inhibition mechanism and mode of allosteric signal transduction. This work presents ten high resolution crystal structures of Cj-DHDPS and the mutant Y110F-DHDPS with various substrates and inhibitors, including the first reported structure of DHDPS with ASA bound to the active site. As a body of work these structures reveal residues and conformational changes which contribute to the inhibition of the enzyme. Understanding these structure function relationships will be valuable for the design of future antibiotic lead compounds. When an inhibitor binds to the allosteric site there is meaningful shrinkage in the solvent accessible volume between 33% and 49% proportional to the strength of inhibition. Meanwhile at the active site the solvent accessible volume increases between 5% and 35% proportional to the strength of inhibition. Furthermore, inhibitor binding at the allosteric site consistently alters the distance between hydroxyls of the catalytic triad (Y137-T47-Y111') which is likely to affect local pKa's. Changes in active site volume and modification of the catalytic triad would inhibit the enzyme during the binding and condensation of ASA. The residues H56, E88, R60 form a network of hydrogen bonds to close the allosteric site around the inhibitor and act as a lid. Comparison of ʟ-lysine and bislysine bound to wt-DHDPS and Y110F-DHDPS indicates that enhanced inhibition of bislysine is most likely due to increased binding strength rather than altering the mechanism of inhibition. When ASA binds to the active site the network of hydrogen bonds among H56, E88 and R60 is disrupted and the solvent accessible volume of the allosteric site expands by 46%. This observation provides some explanation for the reduced affinity of ʟ-lysine in high ASA concentrations. ʟ-Lysine, but not other inhibitors, is found to induce dynamic domain movements in the wt-DHDPS. These domain movements do not appear to be essential to the inhibition of the enzyme but may play a role in cooperativity between monomers or governing protein dynamics. The moving domain connects the allosteric site to the dimer-dimer interface. Several residues at the weak dimer interface have been identified as potentially involved in dimer-dimer communication including: I172, D173, V176, I194, Y196, S200, N201, K234, D238, Y241, N242 and K245. These residues are not among any previously identified as important for formation of the quaternary structure.

Résumé : Le Campylobacter est la première cause de gastro-entérites bactériennes dans les pays industrialisés. La grande majorité des cas sont des infections sporadiques dont la source est rarement identifiée. Le Campylobacter fait partie de la flore intestinale normale d’une large diversité d’animaux et peut également se retrouver dans l’eau. Le but de mon projet de recherche était d’étudier l’épidémiologie clinique et moléculaire des infections à Campylobacter en Estrie afin de déterminer les principales sources d’infections sporadiques et de comparer les génotypes des isolats de Campylobacter selon les différentes niches écologiques. Nous avons déterminé le profil de sensibilité aux antibiotiques d’isolats de différentes sources. Nous avons observé un haut taux de résistance à l’érythromycine et à la tétracycline et un faible taux de résistance à la ciprofloxacine chez les isolats de poulet, pouvant refléter l’utilisation de ces antibiotiques dans cet élevage. Le fait que le taux de résistance à l’érythromycine parmi les isolats humains soit significativement moins élevé que chez les isolats de poulet suggérait l’importance d’autres sources de Campylobacter chez l’humain. Afin de déterminer quelle méthode de typage moléculaire serait la mieux adaptée pour notre devis de recherche, nous avons comparé quatre méthodes (AFLP, MLST, typage du gène fla et EGCP). Seul le MLST a pu attribuer des isolats humains à des niches écologiques particulières comme le poulet, le lait cru et l’eau. Afin d’optimiser la technique de MLST, nous avons développé un système complémentaire basé sur le HRM, qui est beaucoup plus rapide et moins coûteux que le MLST. Nous avons démontré que le HRM a le potentiel de complémenter les méthodes d’analyses basées sur du séquençage pour l’étude des mutations ponctuelles et de faciliter une vaste gamme d’études basées sur des méthodes génotypiques, telle la détection de mutations ponctuelles qui confèrent de la résistance aux antibiotiques. Nous avons entrepris par la suite une étude cas-cas et un vaste projet d’isolement et de caractérisation moléculaire de souches de Campylobacter en Estrie, afin de véritablement cerner les mécanismes de transmission de la bactérie et de comparer les sources d’infections sporadiques chez les cas acquis en régions rurales vs urbaines. Nous avons confirmé que le poulet était responsable de la majorité des cas de campylobactérioses. Cependant, nos résultats suggèrent que la saisonnalité ainsi que le gradient urbain-rural de la campylobactériose sont dus à l’exposition aux souches bovines, particulièrement chez le groupe d’âge des 15-34 ans via l’exposition professionnelle. Par la détermination des sources d’infections, nous avons établi des pistes d’interventions utilisables par les autorités de santé publique, afin de diminuer l’incidence de la campylobactériose au Québec. / Abstract : Campylobacteriosis is the leading notifiable enteric disease in industrialised countries. It colonizes a wide range of animal which in turn spread the disease. The majority of campylobacteriosis cases are sporadic infections for which the source is rarely apparent. The main goal of my research project is to determine contamination sources of Campylobacter in the Eastern Townships, to identify the sources and routes of transmission and to establish the main sources of sporadic infections. We determined antimicrobial susceptibility profiles of Campylobacter isolates in order to predict which bacterial population will be resistant, caused by antimicrobial selective pressure administered to the host. High levels of resistance of chicken isolates to erythromycin and tetracycline, and low levels of resistance to ciprofloxacin reflect the use of the former antibiotics in animal husbandry. The fact that the erythromycin and tetracycline resistance levels were significantly lower among human isolates suggests that other transmission sources are important for human infection. In order to determine which molecular typing method will be the most relevant for our research design, we compared four typing methods (AFLP, MLST,/7a typing and PFGE). Only MLST has the potential to link isolates to a particular ecological niche, such as chicken, raw milk and water. In order to optimize MLST, we developed a complementary system based on HRM. We demonstrated that HRM has the potential to complement the analysis methods based on sequencing for SNP and facilitate a wide range of studies based on genotypic methods. We have subsequently undertaken a major project of isolation and molecular characterization of Campylobacter in the Eastern Townships, in order to truly understand the mechanisms of transmission of the bacteria and determine the source of sporadic cases. We confirmed that chicken was responsible for the majority of cases of campylobacteriosis. However, we have shown that the urban-rural gradient of campylobacteriosis in the Eastern Townships could be explained by exposure to bovine, especially for the 15-34 year old age group through occupational exposure. By the identification of infection sources, we proposed courses of action that could be used by public health authorities to reduce the incidence of campylobacteriosis in Quebec.

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.