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Pombos (Columba livia) são aves exóticas no Brasil que coabitam de forma crescente com a população urbana e de animais de criação, podendo ser reservatórios, portadoras e/ou transmissoras de agentes patogênicos para outras espécies. Neste trabalho foi realizado sequenciamento de alto desempenho buscando identificar o viroma de pombos de vida livre. No primeiro estudo foram caracterizados sete genomas completos de pigeon circovirus (PiCV), sequenciados a partir de amostras de soro de pombos das diferentes regiões amostradas. Os dados permitiram análises sobre a variabilidade genômica deste vírus, os quais apresentam similaridade genética com PiCV previamente relatados na Europa. Além disso, foram identificados pontos propensos a eventos de recombinação em ambas as ORFs (Rep e Cap), apesar do elevado grau de conservação. No segundo estudo que compõe essa tese, foram reportados e analisados dois genomas de girovírus - PiGyV_RS/TQ e PiGyV_RS/RG. Por apresentarem baixa identidade com vírus conhecidos, sugere-se tratar de um novo girovírus circulante em pombos de vida livre com nome sugerido de Pigeon Gyrovirus (PiGyV). O terceiro estudo realizado apresenta os resultados dos viromas obtidos dos soros de 137 pombos coletados em sete regiões geograficamente distintas da região sul do Brasil. O total de reads sequenciadas por região variou de 325.182 a 1.243.426, e em média, 43% destas apresentaram identidade com sequências virais depositadas no GenBank. Dentre os contigs virais, 90,8% apresentaram identidade com sequências de genomas de vírus eucarióticos representativos de seis famílias virais: Circoviridae (a mais abundante), Flaviviridae, Anelloviridae, Adenoviridae, Parvoviridae e Coronaviridae. Alguns dos genomas identificados podem representar agentes de potencial impacto à saúde humana e animal, como os vírus pertencentes aos gêneros Hepacivirus e Pegivirus. Estes resultados contribuem para um maior entendimento dos vírus que circulam em pombos de vida livre, além de ter contribuído para a descoberta de vírus que, até o presente momento, não tinham sido relatados no Brasil. Pigeons (Columba livia) are exotic birds in Brazil that increasingly cohabit with urban population and rural animals, being potential reservoirs, carriers and/or transmitters of pathogens for other species. In this work, high performance sequencing was carried out to identify the pigeon viroma of free life. In the first study, seven complete genomes of pigeon circovirus (PiCV) were characterized, sequenced from serum samples of pigeons from different sampled regions. The data allowed analyzes on the genomic variability of this virus, which have genetic similarity with PiCV previously reported in Europe. In addition, points prone to recombination events were identified in both ORFs (Rep and Cap), despite the high degree of conservation. In the second study that composes this thesis, two genomes of gyrovirus - PiGyV_RS/TQ and PiGyV_RS/RG were reported and analyzed. Because they have low identity with known viruses, it is suggested to treat a new circulating gyrovirus in free-living pigeons with the suggested name of Pigeon Gyrovirus (PiGyV). The third study presents the viroma results obtained from sera of 137 pigeons, grouped according to seven sampled regions. The total reads sequenced by region ranged from 325,182 to 1.243,426. In average, 43.0% of the reads showed identity to viral sequences deposited in GenBank. Among viral contigs, 90.8% presented identity to sequences of eukaryotic viral genomes, and the viruses of animal interest were classified into six families: Circoviridae (the most abundant), Flaviviridae, Anelloviridae, Adenoviridae, Parvoviridae and Coronaviridae. It was possible to observe the great diversity of viral families circulating in the serum of the pigeons, some of which have a potential impact on human and animal health, such as viruses belonging to the genus Hepacivirus and Pegivirus. These results contribute to a better understanding of the viruses that circulate in free living pigeons, as well as contributing to the discovery of viruses that, to date, have not been reported in Brazil.

Escherichia coli O157: H7 is one of the most important foodborne pathogens nowadays, since it has been responsible for severe outbreaks worldwide. Even though this food pathogen has been isolated in many countries, Brazilian foods were considered E. coli O157:H7- free until recently. However, the presence of E. coli O157:H7 has been reported in diverse foods produced in Brazil and an increasing number of isolation from cattle feces has been observed, demonstrating that this pathogen is present in different parts of Brazil, and severe foodborne outbreaks may occur in the near future if adequate control measures are not implemented., Escherichia coli O157: H7 is the major foodborne pathogens in the present, since it has been responsible for severe outbreaks food in many countries. Several studies evaluate numerous food samples indicating a low frequency of isolation of E. coli O157:H7 in Brazilian products. However, these data should be interpreted carefully since in Brazil there is no systematic monitoring that might indicate the true situation of the occurrence of this bacteria in food and several clinical cases of Hemolytic Uremic Syndrome (HUS), have been recorded, including one associated with E. coli O157:H7. Moreover, numerous researches has been indicating the increasingly frequent isolation of microorganisms in animal reservoirs, mainly in cattle, suggesting the necessity of monitoring of shiga toxin-producing strains (STEC), because in a globalized world, emerging microorganisms could be rapidly disseminated. The objective of this study is to present the current situation of E. coli O157: H7 in Brazil.