Estudo da variabilidade da microbiota intestinal em murganhos machos ICR durante um ensaio de carcinogénese química do urotélio
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2013-11-15
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A microbiota intestinal é constituída por um ecossistema microbiológico complexo, composto por microrganismos. Tem um importante papel no desenvolvimento do sistema imunológico e da mucosa gastrointestinal após o nascimento.
O objetivo deste trabalho experimental consistiu em investigar a variabilidade da microbiota intestinal em murganhos (Mus musculus) ICR com 4-5 semanas de idade, durante um ensaio de carcinogénese do urotélio. Efetuaram-se dois ensaios, em dois períodos diferentes, sendo denominados de Grupo 1 (primeiro ensaio) e Grupo 2 (segundo ensaio). Em cada grupo efetuaram-se dois subgrupos no Grupo 1 denominados de A1 e B1. Nos animais do subgrupo A1 apenas foi administrado placebo na água durante 12 semanas (controlo) e, no subgrupo B1 os animais foram expostos a N-butil-N-(4-hidroxibutil) nitrosamina (BBN), substância com ação carcinogénica durante 12 semanas na água de bebida (tratamento). No grupo 2 incluíram-se animais no subgrupo A2 onde foi administrado o placebo durante 19 semanas (controlo) e, o subgrupo B2, onde os animais foram expostos a BBN durante 12 semanas na água (tratamento), e depois ao placebo durante as 7 semanas seguintes. Os murganhos foram distribuídos aleatoriamente, em grupos de 3 e 7 animais por 10 gaiolas. Os dois ensaios foram feitos em alturas do ano diferentes. No final de cada ensaio foram recolhidas amostras de fezes (0,015g) para se proceder ao estudo da biodiversidade da microbiota intestinal.
O procedimento experimental de isolamento e identificação foi efetuado pelos métodos de rotina em microbiologia. Os géneros mais identificados foram Bacillus spp. isolados em 59 (98,3%) e Enterococcus spp. que foram encontrados em 38 (63,3%) das amostras. Na comparação entre os dois grupos as diferenças encontradas não foram estatisticamente significativas entre os subgrupos (χ2=0,144; p=0,705), embora a frequência de isolamento fosse significativamente superior no grupo 1 (χ2= 4,593; p=0,032). Neste trabalho também não se isolou Escherichia coli, uma das bactérias mais frequentemente isoladas a nível da microbiota intestinal normal da maioria ou totalidade das espécies existentes.
The intestinal microbiota consists in a complex microbiological ecosystem, composed by microorganisms. It has an important role in the development of the immunologic system and gastrointestinal mucosa after birth. The purpose of this experimental work consisted in investigating the intestinal microbiota variability in house mice (Mus musculus) ICR with 4-5 weeks old, during a trial of urothelium carcinogenesis. Two trials were carried out in two different periods, denominated Group 1 (first trial) and Group 2 (second trial). In both groups were carried out two subgroups, named A1 and B1 in Group 1. The animals in the subgroup A1 were only administered a placebo in the water for 12 weeks (control) and in subgroup B1 the animals were exposed to N-butil-N-(-4-hidributil) nitrosamine (BBN), a substance with carcinogenic action if administered during 12 weeks in the water. In Group 2, animals in subgroup A2 were included, where the placebo was administered for 19 weeks (control) and in subgroup B2, where animals were exposed to BBN in the water for 12 weeks (treatment), and then exposed to the placebo during the next 7 weeks. The house mice were distributed randomly, in groups of 3 and 7 animals in 10 cages. The two trials were carried out in different periods of the year. In the end of every trial, feces were collected (0.015 g) to proceed to the study of intestinal microbiota biodiversity. The experimental procedure of isolation and identification was carried out under the current standard methods in microbiology. The more common genus identified were Bacillus spp., isolated in 59 samples (98.3 %), and Enterococcus spp., which was found in 38 samples (63.3 %). Comparing the two groups, the differences found were not statistically significant between the subgroups (χ 2=0.144; p=0.705), although the frequency of isolation had been significantly superior in Group 1 (χ 2= 4.593; p=0.032). In this study, Escherichia coli, which is one of the most commonly isolated bacteria in the normal intestinal microbiota of the majority or totality of existent species, was not isolated.
The intestinal microbiota consists in a complex microbiological ecosystem, composed by microorganisms. It has an important role in the development of the immunologic system and gastrointestinal mucosa after birth. The purpose of this experimental work consisted in investigating the intestinal microbiota variability in house mice (Mus musculus) ICR with 4-5 weeks old, during a trial of urothelium carcinogenesis. Two trials were carried out in two different periods, denominated Group 1 (first trial) and Group 2 (second trial). In both groups were carried out two subgroups, named A1 and B1 in Group 1. The animals in the subgroup A1 were only administered a placebo in the water for 12 weeks (control) and in subgroup B1 the animals were exposed to N-butil-N-(-4-hidributil) nitrosamine (BBN), a substance with carcinogenic action if administered during 12 weeks in the water. In Group 2, animals in subgroup A2 were included, where the placebo was administered for 19 weeks (control) and in subgroup B2, where animals were exposed to BBN in the water for 12 weeks (treatment), and then exposed to the placebo during the next 7 weeks. The house mice were distributed randomly, in groups of 3 and 7 animals in 10 cages. The two trials were carried out in different periods of the year. In the end of every trial, feces were collected (0.015 g) to proceed to the study of intestinal microbiota biodiversity. The experimental procedure of isolation and identification was carried out under the current standard methods in microbiology. The more common genus identified were Bacillus spp., isolated in 59 samples (98.3 %), and Enterococcus spp., which was found in 38 samples (63.3 %). Comparing the two groups, the differences found were not statistically significant between the subgroups (χ 2=0.144; p=0.705), although the frequency of isolation had been significantly superior in Group 1 (χ 2= 4.593; p=0.032). In this study, Escherichia coli, which is one of the most commonly isolated bacteria in the normal intestinal microbiota of the majority or totality of existent species, was not isolated.
Descrição
Dissertação de Mestrado em Biologia Clínica Laboratorial.
Palavras-chave
Mus musculus , Nitrosamina , Microbiota intestinal , N-butil-N-(4-hidroxibutil)