theresa.j.ochoa@uth.tmc.edu / Article / BACKGROUND: Enteropathogenic Escherichia coli (EPEC) strains are pediatric pathogens commonly isolated from both healthy and sick children with diarrhea in areas of endemicity. The aim of this study was to compare the bacterial load of EPEC isolated from stool samples from children with and without diarrhea to determine whether bacterial load might be a useful tool for further study of this phenomenon. METHODS: EPEC was detected by polymerase chain reaction (PCR) of colonies isolated on MacConkey plates from 53 diarrheal and 90 healthy children aged <2 years. DNA was isolated from stool samples by cetyltrimethylammonium bromide extraction. To standardize quantification by quantitative real-time PCR (qRT-PCR), the correlation between fluorescence threshold cycle and copy number of the intimin gene of EPEC E2348/69 was determined. RESULTS: The detection limit of qRT-PCR was 5 bacteria/mg stool. The geometric mean load in diarrhea was 299 bacteria/mg (95% confidence interval [CI], 77-1164 bacteria/mg), compared with 29 bacteria/mg (95% CI, 10-87 bacteria/mg) in control subjects (P = .016). Bacterial load was significantly higher in children with diarrhea than in control subjects among children <12 months of age (178 vs 5 bacteria/mg; P = .006) and among children with EPEC as the sole pathogen (463 vs 24 bacteria/mg; P = .006). CONCLUSIONS: EPEC load measured by qRT-PCR is higher in diarrheal than in healthy children. qRT-PCR may be useful to study the relationship between disease and colonization in settings of endemicity.

Mucins, synthesised and secreted by goblet cells, possess potential binding sites for both commensal and pathogenic organisms, and may perform a defensive role during establishment of the intestinal barrier in newly hatched chickens. Increasing interest has been directed toward bacterial interactions within the mucus layer, and the mechanisms by which bacterial colonisation can influence mucus composition during early development. This is important, firstly, as a means to understand initiation of infection and secondly, to optimise the gut microflora for enhanced animal production. Currently, information on mucosal-bacterial interactions in poultry is limited. In order to observe the effects of bacterial exposure on intestinal goblet cell mucin production during early development, differences in the small intestine of conventionally-raised (CV) and low bacterial load (LBL) broiler chicks were examined during the first 7 days post-hatch. The initial aim of the study was to construct a small-scale, economical isolator system to hatch and raise chicks in a bacterial-free environment as a means to observe bacterial interactions with the intestinal mucosa in chickens exposed to normal environmental conditions. The design and construction of flexible plastic isolators for incubation and brooding are described, along with methodologies for preparation of eggs for entry into the isolators, incubation and hatching. Two trials were conducted, the first in August 2005 and the second in March 2006. It was found that the isolator system was successful in producing low bacterial load chicks for comparative studies with conventionally raised chicks, without compromising body weight. A histological study was then conducted whereby ileal and jejunal goblet cells were stained with either periodic acid-Schiff or high iron diamine/alcian blue pH 2.5 to discriminate between neutral, sulphated and sialyated acidic mucins. Total goblet cell numbers and goblet cell and villous/crypt morphology were also examined. Bacterial colonisation of CV animals induced an increase in sialic acid moieties in both ileal and jejunal goblet cell such that initiation of these changes occurred at day 3-4 post-hatch. Differences in intestinal morphology were also consistent with other germ-free animal studies. In order to further understand the extent to which bacteria affected mucin composition, purified, isolated oligosaccharide fractions from ileal mucin at d 4 and 7 post-hatch were collected and analysed using mass spectrometry techniques to determine any structural differences in chain length or chain number between LBL and CV animals. No differences in chain length or number were observed between CV and LBL animals at either d 4 or 7 post-hatch with both groups equally displaying chain lengths of both low and high molecular weights. Although structural differences in mucin oligosaccharides were not observed between LBL and CV animals, bacterial binding assays utilising whole ileal sections were employed to determine whether or not the differences in mucin composition between LBL and CV animals during early development may have deterred or enhanced binding of certain bacterial species. Escherichia coli and Lactobacillus salivarius were selected for the experiment. Binding of L. salivarius to ileal sections was very low whereas E. coli binding was greater, and more pronounced in LBL animals, especially at d 7 post-hatch. No statistically significant differences were observed in binding of E. coli to purified ileal mucin from LBL and CV animals at either d 4 or d 7 post-hatch. Correlations between E. coli and L. salivarius adherence to ileal tissue and mucin samples, and goblet cell parameters, were not statistically significant when fitted as co-variates. It was concluded that the changes in mucin composition played a minor role in bacterial adhesion of L. salivarius and this E. coli serotype. In summary, this thesis explores the physiological changes in goblet cell mucin production in response to bacterial exposure post-hatch. The thesis outlines the complexity of mucosal-bacterial interactions which would benefit from the employment of specialised techniques such as nuclear magnetic resonance spectroscopy and microarray technologies to examine a greater range of mucin structures and gene expression. This thesis provides support for future investigations into the influence of intestinal microflora on mucosal and mucin dynamics of poultry and the potential development of prebiotics for use in animal production. / http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1297640 / Thesis (Ph.D.) -- School of Agriculture, Food and Wine, 2007

Orientador: Elisa Helena Giglio Ponsano / Banca: Marcia Marinho / Banca: Aparecida de Fátima Michelin / Resumo: O interesse da população pelo consumo de alimentos saudáveis, práticos e com maior durabilidade é cada vez mais frequente. Para atender a essa demanda, as indústrias de alimentos têm buscado trabalhar com ingredientes naturais, visando minimizar o uso de aditivos sintéticos. O estudo objetivou investigar se a inclusão de diferentes especiarias em hambúrguer bovino afeta o crescimento bacteriano, a oxidação lipídica e as características sensoriais dos produtos. Foram elaboradas 4 formulações de hambúrguer: controle (sem aditivos), açafrão (1%), gengibre (1%) e urucum (1%). Os produtos foram analisados quanto à contagem bacteriana total (CBT) nos dias 0, 7 e 15 (armazenamento a 4 °C) e 0, 15 e 60 (armazenamento a -30 °C) e quanto à rancidez, nos dias 0, 30 e 60 (armazenamento a -30 °C). A aceitação dos atributos sensoriais e a intenção de compra foram avaliadas com o uso de escalas hedônicas. Todos os hambúrgueres formulados com especiarias e mantidos a 4 °C apresentaram menor CBT que a formulação controle, enquanto que, para os armazenados a -30 °C, o mesmo ocorreu apenas com os que continham gengibre. Menores valores de oxidação lipídica foram encontrados nas formulações contendo as especiarias, com 0, 30 e 60 dias de armazenamento a -30 °C. As formulações controle e gengibre lideraram a aceitação dos provadores nos atributos aparência e cor, enquanto que, para os demais atributos, não houve diferença entre as formulações com especiarias. Na intenção de compra, tanto os hambú... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The population's interest in consuming healthier, more practical and durable foods is increasingly frequent. In order to meet this demand, the food industry has sought to work with natural ingredients in order to minimize the use of synthetic additives. The study aimed to investigate if the inclusion of different spices in bovine burger affects bacterial growth, lipid oxidation and sensorial characteristics of the products. Four hamburger formulations were prepared: control (without additives), saffron (1%), ginger (1%) and annatto (1%). The products were analyzed for total bacterial count (TBC) on days 0, 7 and 15 (storage at 4 °C) and 0, 15 and 60 (storage at -30 °C) and, for rancidity, on days 0, 30 and 60 (storage at -30 °C). The acceptance of the sensory attributes and the purchase intent were evaluated using hedonic scales. All burgers formulated with spices and kept at 4 °C had lower TBC than the control formulation, whereas for those stored at -30 °C, the same occurred only with the ginger-made ones. Lower lipid oxidation was found for the formulations containing the spices, with 0, 30 and 60 days of storage at -30 °C. Control and ginger formulations led the acceptance of the tasters for the attributes appearance and color, while for the other attributes no differences among the formulations with spices were detected. In the purchase intention trial, both the ginger-made and the control group burgers aroused greater interest from the tasters. It was concluded that the... (Complete abstract click electronic access below) / Mestre

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No. of bitstreams: 2 Dissertação - Júnnia Pires de Amorim Trindade - 2016.pdf: 4029550 bytes, checksum: 8273cd9d0a5907d8dd17702921026096 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-04-12 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / This experimental study examined silicone tubes coming from care to surgical patients in the perioperative period, chosen randomly. The study was conducted from September to November 2015 and the tubes were derived from the Central Sterile Supply Departments (CSSD) of a large general hospital in the Midwest region of Brazil. The objectives were to validate a method for extraction and quantification of microbial contamination in silicon tubes, checking the microbial charge of silicone tubes immediately after cleaning, and in different storage intervals identify the presence of biofilms on silicone tubing.The study was approved by the Ethics Committee under the protocols No. 1,277,077 and 1,000,946. To validate the method, two new sterile silicone tubing were used, pipe 01 and pipe 02 to 106 were artificially contaminated with bacterial spores of Geobacillus stearothermophilus. The contaminated pipes were filled with sterile water and sealed at the extremities. The tube 02 was submitted to five minutes sonication. The tube 01 has not submitted to this process. Subsequently, the seals were removed and the water collected in 60- mL syringe and filtered through 0.45 Millipore membrane μm in holder for syringe device. Membranes were incubated at 35 ° C for 24 hours in petri dishes containing nutrient agar. After the incubation period, the membranes were removed and placed in test tubes containing 1mL of saline that were submitted to vortexing for five minutes and subjected to handle calibrated technique for quantification of the colony. The sonication proved to be more effective for recovery of micro-organisms. The validated methodology was used for the tubes of the experimental groups (consisting of 10 silicon tubes used in hospital care after the cleaning process), negative control (three new silicone tubes) and positive control (tubes used in assisting during surgery with organic matter visible). The tubes were initially segmented into three fragments: end 01, 02 and a half later and were again targeted to pre-established time intervals zero, 12 and 24 hours in conditions similar to those offered by the study institution. In addition to the groups submitted to microbiological analysis by this method, similar tubes to the experimental group were collected for analysis by scanning electron microscopy (SEM). Among the tubes that were subjected to analysis by SEM, experimental groups were formed (three tubes used in hospital care after the cleaning process), positive control (tubes used without cleaning) and negative (new tubes). There was no statistically significant difference when comparing the means and the ends of the silicone tubing used in hospital care (p> 0.05) in zero periods, 12 and 24 hours. There was an increase of microbial load of the order of a magnitude on the logarithmic scale every 12 hours (p <0.05) in cleaning and storage conditions provided by the institution in experimental and positive control. There was no microbial growth in the negative control group. SEM showed the presence of organic matter that can support microbial growth. / Estudo experimental que analisou tubos de silicone oriundos da assistência ao paciente cirúrgico no período transoperatório, escolhidos aleatoriamente. O estudo foi realizado no período de setembro a novembro de 2015 e os tubos foram oriundos do Centro de Material e Esterilização (CME) de um hospital geral de grande porte da região Centro-Oeste do Brasil. Os objetivos foram validar um método para extração e quantificação da carga microbiana em tubos de silicone, determinar a carga microbiana de tubos de silicone imediatamente após a limpeza e em diferentes intervalos de armazenamento e avaliar a presença de biofilme em tubos de silicone. O estudo foi aprovado pelo Comitê de Ética sob os protocolos nº 1.277.077 e 1.000.946. Para a validação do método foram utilizados dois tubos de silicone novos esterilizados, tubo 01 e tubo 02 que foram artificialmente contaminados com 106 esporos bacterianos de Geobacillus stearothermophilus e em seguida. Os tubos contaminados foram preenchidos com água estéril e vedados nas extremidades. O tubo 02 foi submetido a cinco minutos de sonicação, já o tubo 01 não passou por este processo. Posteriormente, os lacres foram removidos e a água coletada em seringa de 60 mL e filtradas em membrana Millipore 0,45 µm em dispositivo holder para seringa. As membranas foram incubadas em estufa a 35ºC por 24 horas em placas de petri contendo ágar nutriente. Após o período de incubação, as membranas foram removidas e dispostas em tubos de ensaio contendo 1mL de solução salina que foram submetidas a agitação em vórtex por cinco minutos e submetidos a técnica de alça calibrada para quantificação das colônias. A sonicação demonstrou-se mais eficaz para a recuperação dos micro-organismos. A metodologia validada foi utilizada para os tubos dos grupos experimental (composto por 10 tubos de silicone utilizados na assistência hospitalar após o processo de limpeza), controle negativo (três tubos de silicone novos) e controle positivo (tubos usados na assistência transoperatória com matéria orgânica visível). Os tubos foram segmentados inicialmente em três fragmentos: extremidade 01, 02 e meio e posteriormente foram novamente segmentados conforme intervalos de tempo pré- estabelecidos zero, 12 e 24 horas em condições semelhantes às oferecidas pela instituição, local do estudo. Além dos grupos submetidos a análise microbiológica pelo método descrito, Novos tubos em condições semelhantes ao do grupo experimental foram coletados tubos semelhantes ao grupo experimental para análise por microscopia eletrônica de varredura (MEV). Dos tubos submetidos a análise pelo MEV, foram formados grupo experimental (três tubos utilizados na assistência hospitalar após o processo de limpeza), grupos controle positivo (tubos utilizados sem limpeza prévia) e negativo (tubos novos). Não houve diferença estatisticamente significativa quando comparados o meio e as extremidades dos tubos de silicone utilizados na assistência hospitalar (p>0,05) nos períodos zero, 12 e 24 horas. Houve aumento da carga microbiana na ordem de uma grandeza na escala logarítmica a cada 12 horas (p<0,05), nas condições de limpeza e armazenamento proporcionados pela instituição nos grupos experimental e controle positivo. Não houve crescimento microbiano no grupo controle negativo. A MEV mostrou presença de matéria orgânica que pode favorecer o crescimento microbiano.

Mycobacterium tuberculosis, the causative agent of tuberculosis, can manipulate host cell death pathways as virulent strains inhibit apoptosis to protect its replication niche and induce necrosis as a mechanism of escape. In vitro studies revealed that similar to lytic viruses, M. tuberculosis has the ability to induce cytolysis in macrophages when it reaches an intracellular burden of ~25 bacilli. Base on this finding, we proposed the burst size hypothesis that states when M. tuberculosis invades a macrophage at a low multiplicity of infection it replicates to a burst size triggering necrosis to escape the cell and infect naïve nearby phagocytes, propagating the spread of infection. The first part of this study investigated if the in vitro observations of M. tuberculosis cytolysis were relevant to cell death of infected phagocytes during pulmonary tuberculosis in vivo. Mice infected with a low dose of M. tuberculosis revealed during TB disease, the major host cell shifted from one type of phagocyte to another. Enumeration of intracellular bacilli from infected lung cells revealed the predictions of the hypothesis were confirmed by the distribution of bacillary loads across the population of infected phagocytes. Heavily burdened cells appeared nonviable sharing distinctive features similar to infected macrophages from in vitro studies. Collectively, the data indicates that M. tuberculosis triggers necrosis in mononuclear cells when its number reaches the threshold burst size. The previous study showed during the period of logarithmic bacterial expansion, neutrophils were the primary host cell for M. tuberculosis coinciding with the timeframe of the highest rate of burst size necrosis. The second part of this study examined this link by infecting mice with one of four different M. tuberculosis strains ranging in virulence. Mice infected with the most virulent strain had the highest bacterial burden and elicited the greatest number of infected neutrophils with the most extensive lung inflammation and greater accounts of cell death. Treating these mice with a bacteriostatic agent decreased the bacterial load and infected neutrophils in a dose-dependent manner indicating necrosis induced by virulent M. tuberculosis recruited neutrophils to the lungs. Infected neutrophils can serve as a biomarker in tuberculosis as evidenced by poorly controlled infection and increased severity of lung immune pathology.

[ES] Antecedentes: Los patrones de colonización microbiana alterados durante la infancia pueden ser en parte responsables del aumento de enfermedades alérgicas en los países desarrollados. La microbiota intestinal difiere en composición y diversidad durante los primeros meses de vida en niños que luego desarrollan o no una enfermedad alérgica. Sin embargo, poco se sabe sobre la importancia de las respuestas inmunitarias tempranas de la mucosa a la microbiota intestinal en el desarrollo de alergias infantiles. Además, los estudios con respecto al efecto protector de la microbiota de la leche materna en el riesgo de desarrollar alergias no han sido concluyentes. Aunque la cavidad bucal es el primer lugar de encuentro entre la mayoría de los antígenos exógenos y el sistema inmunológico, no existen datos sobre la influencia de las bacterias orales en el desarrollo de alergias durante la infancia. Objetivos: El objetivo general de esta tesis fue evaluar la composición y diversidad microbiana en muestras orales, intestinales y de leche materna, junto con su interacción con IgA, para estudiar el papel de la colonización microbiana durante edades tempranas de la vida en condiciones de salud y de enfermedad alérgica. Sujetos: Los bebés y las madres incluidas en este estudio forman parte del ensayo aleatorio doble ciego más grande de Suecia, entre 2001 y 2003, donde se evaluaron los posibles efectos preventivos sobre la alergia de Lactobacillus reuteri ATCC 55730 hasta los 2 y 7 años. En esta tesis, utilizamos muestras de heces recogidas a los 1 y 12 meses, y muestras orales de bebés, obtenidas longitudinalmente a los 3, 6, 12, 24 meses y 7 años. Además, analizamos muestras de leche materna, recogidas a un mes después del parto de las madres correspondientes. Métodos: Se utilizaron tecnologías de secuenciación de segunda generación dirigidas al gen 16S rARN, en combinación con citometría de células marcadas por fluorescencia, para abordar las respuestas de IgA de la mucosa hacia las bacterias intestinales y de la leche materna. Además, se utilizó la secuenciación del gen 16S para describir la colonización oral de la microbiota, en muestras de saliva, de niños que desarrollaron alergias o de aquellos que se mantuvieron sanos. Los niveles de carga bacteriana en diferentes hábitats microbianos se obtuvieron mediante la metodología de qPCR y los niveles totales de IgA de las muestras de heces se determinaron mediante inmuno-ensayo ELISA. Resultados y conclusión: La colonización de la cavidad bucal durante la infancia temprana es progresiva, aumenta en complejidad con el tiempo, y varios factores externos parecen influir en gran medida en la maduración de la microbiota oral, ya sea con un impacto a corto o largo plazo. Los cambios tempranos en la composición microbiana oral parecen influir en la maduración inmune y el desarrollo de alergias en la infancia, y la presencia de especies bacterianas específicas puede ser importante para este proceso. Además, las respuestas de IgA alteradas hacia la microbiota intestinal durante la infancia precedieron a las manifestaciones de asma y alergia durante los primeros 7 años de vida, y el consumo de leche materna con una riqueza microbiana reducida en el primer mes de vida puede aumentar el riesgo de desarrollar alergia durante la infancia. Los hallazgos observados en la presente tesis deben confirmarse en cohortes más grandes y la importancia de los factores ambientales postnatales para el desarrollo temprano de la microbiota debe abordarse más a fondo. Las investigaciones futuras deben ir más allá de la caracterización de la composición de la comunidad bacteriana e investigar los mecanismos funcionales entre los microorganismos colonizadores tempranos, la maduración inmunitaria y la alergia, así como el desarrollo del asma durante la infancia. / [CAT] Antecedents: S'ha proposat que els patrons de colonització microbiana alterats durant la infància podrien ser en part els responsables de l'augment de malalties al·lèrgiques als països desenvolupats. La microbiota intestinal difereix en composició i diversitat durant els primers mesos de vida en els nens que després van desenvolupar una malaltia al·lèrgica. No obstant això, poc es sap sobre la importància de les respostes immunes de la mucosa a la microbiota intestinal en el desenvolupament d'al·lèrgies infantils. A més, les investigacions amb relació a l'efecte protector de la microbiota de la llet materna en el risc de desenvolupar al·lèrgies no han sigut concloents. Encara que la cavitat bucal és el primer lloc de trobada entre la majoria dels gèneres externs i el sistema immunològic, encara no s'ha descobert la influència dels bacteris en el desenvolupament d'una al·lèrgia durant la infància. Objectius: L'objectiu general d'aquesta tesi va ser avaluar la composició microbiana i la diversitat de mostres orals, fecals i llet materns, juntament amb la seva interacció amb IgA, per estudiar el paper del desenvolupament microbià durant el període de la infància primerenca a la salut i la malaltia al·lèrgica. Subjectes: Les mares i xiquets inclosos en aquest estudi formen part d'un estudi aleatori doble-cec a Suècia, entre el 2001 i el 2003, on es van avaluar els possibles efectes preventius de la suplementació amb Lactobacillus ATCC 55730 fins als 2 i 7 anys. En aquesta tesi, s'utilitzaren mostres de bebès arreplegades longitudinalment, obtinguts a 1 i 12 mesos, 3, 6, 12, 24 mesos i 7 anys, respectivament. A més, s'analitzaren les mostres de llet materna, arreplegades a un mes postpart de les corresponents mares. Mètodes: S'han utilitzat tecnologies de seqüenciació de nova generació dirigides al ARNr 16S, en combinació amb la classificació de les cèl·lules activades, per abordar les respostes de la mucosa cap als bacteris intestinals i de la llet materna. A més, s'utilitzà la seqüenciació d'Illumina MiSeq del gen 16S per descriure la colonització microbiana oral, i es van obtenir mostres longitudinals de saliva de menuts que varen desenvolupar al·lèrgies i d'alguns que es van mantenir saludables. Els nivells de càrrega bacteriana en diferents nínxols microbians s'han obtingut mitjançant la metodologia de qPCR i els nivells totals d'IgA de les mostres fecals es determinaren mitjançant l'immunoassaig ELISA. Resultats i conclusions: La colonització de la cavitat bucal durant la primera infància és transitòria, augmenta la seva complexitat amb el temps, i diversos factors externs influeixen en gran mesura el procés de maduració de la microbiota oral, amb un impacte a curt i llarg termini. Els canvis primerencs en la composició microbiana oral pareixen influir en la maduració del sistema immunològic i el desenvolupament d'al·lèrgies a la infància, així com la presència d'espècies bacterianes específiques pot ser important per a aquest progrés. A més, les respostes d'IgA alterades cap a la microbiota intestinal durant la infància precedeixen a les manifestacions relatives a la malaltia asmàtica i al·lèrgiques durant els primers 7 anys de vida. Per altra banda, el consum de llet materna amb una microbiota de riquesa reduïda al primer mes de vida podria augmentar el risc de desenvolupar al·lèrgia durant la infància. Els resultats observats en aquest estudi haurien de confirmar-se en cohorts humanes més grans i la importància dels factors ambientals post natals que influeixen en el desenvolupament de la microbiota primerenca han de ser més estudiats. Les investigacions futures deuen anar més enllà de la caracterització de la composició de la comunitat bacteriana i investigar els mecanismes funcionals entre els microorganismes colonitzadors primerencs, la maduració del sistema immunològic i el desenvolupament de l'al·lèrgia i l'asma durant la in / [EN] Background: It has been proposed that altered microbial colonization patterns during infancy may be partly responsible for the increase of allergic diseases in developed countries. The gut microbiota differs in composition and diversity during the first months of life in children who later do or do not develop allergic disease. However, little is known about the significance of early mucosal immune responses to the gut microbiota in childhood allergy development, and the findings regarding the protective effect of breastmilk microbiota in the risk of allergy development have been inconclusive. Furthermore, even though the oral cavity is the first site of encounter between a majority of foreign antigens and the immune system, the influence of oral bacteria on allergy development during childhood has not yet been reported. Objectives: The general aim of this thesis was to assess the microbial composition and diversity of oral, fecal and breastmilk samples, together with its interaction with IgA, in order to study the role of microbial development during early childhood in health and allergic disease. Subjects: The infants and mothers included in this study were part of a larger randomized double-blind trial in Sweden, between 2001 and 2003, where potential allergy preventive effects of Lactobacillus reuteri ATCC 55730 were evaluated until 2 and 7 years of age. In this thesis, we used longitudinally collected stool and oral samples from infants, obtained at 1 and 12 months and 3, 6, 12, 24 months and 7 years of age, respectively. Furthermore, we analyzed breastmilk samples, collected at one month post partum, from the corresponding mothers. Methods: Next-generation sequencing technologies targeting the 16S rRNA gene, in combination with cell activated cell sorting, were used in order to address mucosal IgA responses towards gut and breastmilk bacteria. Furthermore, sequencing of the 16S rRNA gene was used in order to describe oral microbiota colonization, in longitudinally obtained saliva samples, from children developing allergy or staying healthy. Bacterial load levels in different microbial habitats were obtained by qPCR methodology and total IgA levels of stool samples were determined by ELISA immunoassays. Results and conclusion: Colonization of the oral cavity during early childhood is transitional, increasing in complexity with time, and several external factors appear to greatly influence oral microbiota maturation, having either a short or a long-term impact. Early changes in oral microbial composition seem to influence immune maturation and allergy development in childhood, and the presence of specific bacterial species may be important for this progress. Furthermore, altered IgA responses towards the gut microbiota during infancy preceded asthma and allergy manifestations during the first 7 years of life, and consumption of breastmilk with a reduced microbial richness in the first month of life may increase the risk for allergy development during childhood. Findings observed here need to be confirmed in larger cohorts and the importance of postnatal environmental factors for early microbiota development should be addressed further. Future research should go beyond characterization of bacterial community composition and investigate the functional mechanisms between early colonizing microorganisms, immune maturation and allergy and asthma development during childhood. / Dzidic, M. (2019). Microbiota development and mucosal IgA responses during childhood in health and allergic disease [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/125479 / TESIS