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Memoria para optar al Título Profesional de Médico Veterinario. / Este estudio proporciona información importante sobre la incidencia de Salmonella en gatos, específicamente aquellos criados como mascotas en la Región Metropolitana de Santiago. El objetivo del estudio, fue buscar una incidencia relativa asociada a gatos criados como mascotas, marca un primer paso, que permitirá en un futuro próximo más investigación sobre el tema y, así, lograr una mejor vigilancia en lo que respecta Salmonella en mascotas y animales de compañía. Las muestras se obtuvieron de gatos residentes en las comunas de Puente Alto, Recoleta, Estación Central, Las Condes, Providencia y Ñuñoa, y fueron tomadas durante el periodo comprendido entre agosto de 2016 y octubre de 2017. En total, fueron 342 las muestras de heces recolectadas. Lo que se observó fue una incidencia total de 0%, ya que ningún gato resultó positivo al método microbiológico utilizado. La incidencia encontrada en el presente estudio es comparable con la bibliografía, en los que se describe una incidencia de 0,5% y se asemeja bastante a lo que se ha visto en países desarrollados, con estudios sobre el tema en sus poblaciones de perros y gatos, como es el caso de EE.UU. con una incidencia del 0,6%. Vale decir que no existen estudios de incidencia en lo que respecta a este ámbito en Chile / The present study it provides important information about the incidence of Salmonella in cats, specifically reared as pets in the Metropolitan Region of Santiago. It is worth mentioning that there are no prevalence studies with regards to this issue in Chile, and the aim of the study to look for a relative incidence associated with cats reared as pets, is a first step that allows more research in the near future on the subject, and thus, achieve better surveillance with regard to pets. Samples came from the districts of Puente Alto, Recoleta, Estación Central, Las Condes, Providencia and Ñuñoa, and were taken during the period between August 2016 and October 2017. There were 342 samples of stool collected, from which 308 were used for the study. A total incidence of 0% was observed, since no cat was positive to the microbiological method used. The incidence found in the present study is comparable to post-1980 studies in which an incidence of 1.9% is described and it closely resembles what has been seen in developed countries, with incidence studies in their populations of dogs and cats, as it is the case of the USA with an incidence of 0.6%

by Ng Wai-Leung. / Thesis submitted in: August 1997. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references (leaves 135-144). / Title page --- p.i / Thesis Committee --- p.ii / Abstract --- p.iii / Acknowledgments --- p.v / Abbreviations --- p.vi / Table of contents --- p.vii / List of figures --- p.x / List of tables --- p.xiii / Chapter Chapter 1. --- General introduction --- p.1 / Chapter Chapter 2. --- Literature review / Chapter 2.1 --- Biosynthesis of deoxyribonucleotide triphosphates --- p.3 / Chapter 2.2 --- Ribonucleotide reductase --- p.6 / Chapter 2.2.1 --- Class I ribonucleotide reductase --- p.6 / Chapter 2.2.2 --- Class II ribonucleotide reductase --- p.13 / Chapter 2.2.3 --- Class III ribonucleotide reductase --- p.14 / Chapter 2.3 --- Proposed mechanism for ribonucleotide reduction --- p.17 / Chapter 2.4 --- Allosteric control of ribonucleotide reductase --- p.21 / Chapter 2.4.1 --- Allosteric control of class I ribonucleotide reductase --- p.21 / Chapter 2.4.2 --- Allosteric control of class II and class III ribonucleotide reductases --- p.23 / Chapter 2.5 --- Evolution of ribonucleotide reductase --- p.25 / Chapter 2.6 --- Central metabolism pathways of enteric bacteria --- p.28 / Chapter 2.7 --- Regulation of gene expression by oxygen in enteric bacteria --- p.33 / Chapter 2.7.1 --- Regulation of gene expression by Fnr --- p.33 / Chapter 2.7.2 --- Regulation of gene expression by AcrAB --- p.39 / Chapter 2.7.3 --- Regulation of gene expression by NarXL and NarQP --- p.42 / Chapter 2.7.4 --- Other aspects in anaerobic gene expression --- p.45 / Chapter 2.7.5 --- Relationship between NrdD and anaerobic metabolism --- p.45 / Chapter 2.8 --- Objectives --- p.46 / Chapter Chapter 3. --- Molecular cloning and sequencing of nrdDG operon from Salmonella typhimurium / Chapter 3.1 --- Introduction --- p.47 / Chapter 3.2 --- Material and methods --- p.48 / Chapter 3.2.1 --- Bacterial strains and bacteriophages --- p.48 / Chapter 3.2.2 --- Culture media --- p.48 / Chapter 3.2.3 --- Preparation of lambda lysate and phage DNA --- p.48 / Chapter 3.2.3.1 --- Plating out pf lambda phage and preparation of plate lysate --- p.48 / Chapter 3.2.3.2 --- Preparation of lambda lysate stock --- p.49 / Chapter 3.2.3.3 --- Preparation of lambda phage DNA --- p.50 / Chapter 3.2.4 --- Long distance polymerase chain reaction (LD-PCR) of nrdDG gene fragment --- p.51 / Chapter 3.2.5 --- Restriction enzyme digestion of LD-PCR products and subcloning of restriction fragments --- p.52 / Chapter 3.2.6 --- Confirmation of recombinants by colony-PCR --- p.53 / Chapter 3.2.7 --- Preparation of plasmid DNA by alkaline lysis using Wizard´ёØ Plus Miniprep DNA Purification System (Promega) --- p.54 / Chapter 3.2.8 --- DNA cycle sequencing by using dye-labeled dideoxy chain terminator and data collection --- p.55 / Chapter 3.2.9 --- Computer software for analyzing and manipulating DNA sequences --- p.57 / Chapter 3.3 --- Results --- p.59 / Chapter 3.3.1 --- Preparation of lambda DNA --- p.59 / Chapter 3.3.2 --- Long distance PCR amplification of nrdDG from lambda DNA --- p.59 / Chapter 3.3.3 --- Restriction digestion of LD-PCR products --- p.61 / Chapter 3.3.4 --- Subcloning of LD-PCR restriction fragments --- p.61 / Chapter 3.3.5 --- Miniprep of plasmid DNA from recombinants and verification of nrdDG identities --- p.64 / Chapter 3.3.6 --- Nucleotide sequence of nrdDG --- p.66 / Chapter 3.4 --- Discussions --- p.72 / Chapter 3.4.1 --- Sequence analysis of S. typhimurium nrdDG --- p.72 / Chapter 3.4.2 --- Experimental design --- p.79 / Chapter Chapter 4. --- Transcriptional regulation of anaerobic ribonucleotide reductase in Salmonella typhimurium in aerobic and anaerobic environments / Chapter 4.1 --- Introduction --- p.84 / Chapter 4.2 --- Materials and methods --- p.86 / Chapter 4.2.1 --- Bacteria and bacteriophages strains / Chapter 4.2.2 --- Culture media --- p.86 / Chapter 4.2.3 --- Construction and characterization of oxrA mutant --- p.87 / Chapter 4.2.3.1 --- Preparation of P22 lysate of TN2336 --- p.87 / Chapter 4.2.3.2 --- P22 transduction for construction of oxrA mutant --- p.87 / Chapter 4.2.3.3 --- Characterization of oxrA mutant --- p.87 / Chapter 4.2.4 --- Extraction of bacterial RNA by hot phenol method --- p.88 / Chapter 4.2.5 --- Formaldehyde gel electrophoresis of RNA --- p.88 / Chapter 4.2.6 --- Reverse transcriptase polymerase chain reaction (RT-PCR) of nrdD transcript --- p.89 / Chapter 4.2.7 --- Transfer of DNA/RNA to solid support --- p.90 / Chapter 4.2.7.1 --- Transfer of DNA to solid support by Southern blotting --- p.90 / Chapter 4.2.7.2 --- Transfer of RNA to solid support by Northern blotting --- p.91 / Chapter 4.2.7.3 --- RNA Dot blot --- p.91 / Chapter 4.2.8 --- Preparation of radioactive-labeled probes for hybridization --- p.92 / Chapter 4.2.8.1 --- Synthesis of radioactive-labeled probes by labeling --- p.92 / Chapter 4.2.8.2 --- Preparation of RNA probe by in vitro transcription --- p.93 / Chapter 4.2.9 --- Hybridization and membrane washing conditions --- p.95 / Chapter 4.2.10 --- Normalization of samples by 16S ribosomal RNA (rRNA) --- p.95 / Chapter 4.3 --- Results --- p.97 / Chapter 4.3.1 --- Preparation of RNA --- p.97 / Chapter 4.3.2 --- RT-PCR of nrdD transcript --- p.97 / Chapter 4.3.3 --- Northern blot analysis of nrdD transcript --- p.103 / Chapter 4.3.4 --- Dot blot hybridization analysis of nrdD expression in an oxrA mutant --- p.103 / Chapter 4.4 --- Discussions --- p.107 / Chapter 4.4.1 --- Expression of nrdD of S. typhimurium in aerobic and anaerobic environments --- p.107 / Chapter 4.4.2 --- Experimental design --- p.110 / Chapter Chapter 5. --- Characterization of nrdD::Tn10 mutant of S. typhimurium / Chapter 5.1 --- Introduction --- p.112 / Chapter 5.2 --- Materials and methods --- p.112 / Chapter 5.2.1 --- Bacteria and bacteriophages strains --- p.113 / Chapter 5.2.2 --- Transduction of zzz-3875::Tn10 to S. typhimurium --- p.113 / Chapter 5.2.3 --- Characterization of zzz-3875::Tn10 by Southern hybridization --- p.113 / Chapter 5.2.3.1 --- Preparation of genomic DNA from S. typhimurium --- p.113 / Chapter 5.2.3.2 --- Restriction enzyme digestion of genomic DNA and Southern hybridization --- p.114 / Chapter 5.2.4 --- Characterization of growth pattern of nrdD::Tn10 mutant --- p.115 / Chapter 5.3 --- Results --- p.116 / Chapter 5.3.1 --- Characterization of zzz-3 875: :Tn7 0 in S. typhimurium --- p.116 / Chapter 5.3.2 --- Characterization of growth pattern of nrdD mutant --- p.120 / Chapter 5.4 --- Discussions --- p.125 / Chapter Chapter 6. --- General Discussions / Chapter 6.1 --- General discussions --- p.131 / Chapter 6.2 --- Further studies --- p.134 / References --- p.135

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Salmonella enterica subsp. enterica sorovar Derby (S. Derby) é um dos sorovares mais frequentemente detectados na cadeia produtiva de suínos na região sul do Brasil. Estudos prévios indicaram que isolados de S. Derby apresentando perfis similares de resistência a antimicrobianos estavam circulando ao longo dos anos nesta região. A sobrevivência de Salmonella no ambiente e a persistência no hospedeiro são facilitadas pela sua habilidade em formar biofilmes. Desta forma, o objetivo deste trabalho foi identificar a presença de grupos clonais entre 140 isolados de S. Derby coletados ao longo de um período de dez anos de diferentes origens da cadeia produtiva de suínos (linfonodos, conteúdo intestinal, ambiente e produtos suínos). Para tanto, o perfil de resistência a antimicrobianos, através de dois conceitos distintos de avaliação de resistência (valores ECOFF e valores de breakpoint), a habilidade em formar biofilmes e a caracterização genotípica por macro-restrição (PFGE) foram avaliados. A determinação do MIC foi realizada em todos os isolados, frente aos seguintes antimicrobianos: ácido nalidíxico, ampicilina, cefotaxima, ceftazidima, ciprofloxacina, colistina, florfenicol, gentamicina, estreptomicina e tetraciclina. Para avaliar a capacidade de S. Derby em formar biofilmes, três metodologias foram aplicadas: i. morfologia de colônia em ágar contendo Vermelho Congo, para determinar a detecção fenotípica de fímbria curli e celulose; ii. formação de biofilme na interface ar-líquido em caldo LB; iii. aderência em microplacas de poliestireno de 96 poços. No total, apenas 17 (12,1%) isolados puderam ser classificados como suscetíveis a todos os antimicrobianos testados. As maiores frequências de populações “non-Wild Type” (nWT) foram observadas frente a tetraciclina (75,7%), estreptomicina (70%) e colistina (11,4%), enquanto que não foram detectadas populações nWT para ciprofloxacina, ceftazidima e gentamicina. Multi-resistência (resistência a ≥ 3 antimicrobianos; de acordo com valores de breakpoint) foi detectada em 8,6% dos isolados. Em ágar contendo Vermelho Congo, três diferentes morfologias de colônia foram observadas. A morfologia Rdar (vermelha, seca e rugosa) foi a mais frequente, sendo detectada em 59 isolados (42,1%); enquanto que as morfologias Saw (branca e mucoide) e Pdar (rosa, seca e rugosa) foram observadas em 46 (32,9%) e em 35 (25%) dos isolados, respectivamente. Os morfotipos Rdar e Pdar, que em conjunto albergaram a maioria dos isolados, são considerados os mais usualmente observados em isolados de Salmonella capazes de formar biofilme. A formação de película rígida, sem dispersão por agitação, foi observada em 24 amostras (17,1%) em caldo LB convencional e em 78 amostras (55,7%) em caldo LB low salt, sendo todas pertencentes aos morfotipos Rdar ou Pdar. Em placas de poliestireno de 96 poços, um grande número (n=96; 68,6%) dos isolados foram fracamente ou moderadamente produtores de biofilme, incluindo todos os isolados que apresentaram os morfotipos Rdar e Pdar. Através dos perfis de formação de biofilme e de resistência a antimicrobianos observados, 36 isolados foram selecionados para macro-restrição por eletroforese em campo pulsado (PFGE). Destas, 27 foram agrupadas em 11 pulsotipos que apresentavam mais de uma cepa com 100% de similaridade. Desta forma, foi possível identificar clones e cepas intimamente relacionadas de S. Derby que circularam em granjas, matadouros-frigoríficos e foram encontrados em alimentos ao longo de uma década. / Salmonella enterica subsp. enterica serovar Derby (S. Derby) is one of the serovars most frequently detected in the swine production chain of southern Brazil. Previous studies indicated that isolates of S. Derby displaying similar antimicrobial resistance profiles circulated over the years in this region. Survival of Salmonella in the environment and persistence in the host are facilitated by the ability to form biofilms. Thus, the aim of this study was to identify the presence of clonal groups between 140 S. Derby isolates collected over a ten-year period from various porcine origins (lymph nodes, intestinal content, environment and pork). Therefore, the antimicrobial resistance profile, through two distinct concepts of resistance evaluation (ECOFF value and breakpoint value), the ability to form biofilm and the genotypic characterization by macro-restriction (PFGE) were evaluated. MIC determinations were performed on all isolates, against the following antimicrobials: nalidixic acid, ampicillin, cefotaxime, ceftazidime, ciprofloxacin, colistin, florfenicol, gentamicin, streptomycin and tetracycline. To evaluate the S. Derby ability to form biofilm, three methods were applied: i. colony morphology on Congo Red agar, to determine the phenotypic detection of curli fimbriae and cellulose; ii. biofilm formation in liquid-air interface of LB broth; iii. adherence on a 96-well polystyrene microtiter plate. In total, only 17 (12.1%) isolates were classified as susceptible to all antimicrobials tested. The highest frequencies of non-Wild Type (nWT) populations were observed against tetracycline (75.7%), streptomycin (70%) and colistin (11.4%), whereas there were no detectable nWT population to ciprofloxacin, ceftazidime and gentamicin. Multidrug resistance (resistance to ≥ 3 antimicrobials) was detected in 8.6% of isolates. On Congo Red agar, three different colony morphology types were observed. The Rdar type (read, dry and rough) was the most frequent, being detected in 59 isolates (42.1%); while Saw (white and smoth) and Pdar (pink, dry and rough) types were observed in 46 (32.9%) and 35 isolates (25%), respectively. The Rdar and Pdar types, which together encompassed the majority of the isolates, are considered the most often observed in Salmonella isolates able to form biofilm. The formation of a rigid pellicle, which could not be dispersed by agitation, was observed in 24 (17.1%) isolates in conventional LB broth and in 78 (55.7%) isolates in low salt LB broth, all belonging to morphotypes Rdar or Pdar. On 96-well polystyrene microtiter plate, a larger number (n=96; 68.6%) of isolates showed to be weak or moderate biofilm producers, including all isolates that showed the Rdar and Pdar type. Through the biofilm and resistance profiles observed, 36 isolates were selected for macro-restriction for pulsed-feld gel electrophoresis (PFGE). Of these, 27 isolates were clustered in 11 pulsotypes which presented more than one strain with 100% of similarity. Therefore, was possible to identify clones and strains closely related of S. Derby that circulated in pig farms, slaughter plants and encountered in foods along a decade.

A boa qualidade do ar é fator essencial para manutenção da saúde humana e ambiental. O material particulado atmosférico é um poluente do ar que consiste de uma variedade de substâncias orgânicas e inorgânicas, entre as quais, algumas apresentam características genotóxicas. O ramo petroquímico é um importante componente da atividade industrial do estado do Rio Grande do Sul, Brasil, com histórico de emissões prejudiciais à qualidade do ar. O presente estudo objetivou avaliar os efeitos biológicos associados à dispersão de material particulado atmosférico inalável em área sob influência de um complexo petroquímico, integrando os resultados de biomonitoramento ambiental e humano através de biomarcadores de genotoxicidade. Amostras de material particulado foram coletadas em área de característica mista rural, urbana e industrial, utilizando filtros de membrana de Teflon e amostradores de grandes volumes de ar, semanalmente, por períodos de 24hs. Partículas inaláveis finas (MP2,5) foram amostradas em dois locais– NO e NE - posicionados na primeira e segunda direção preferencial dos ventos na região de estudo, a 2,5Km de distância da principal fonte emissora da central de matérias-primas do complexo petroquímico. Em um terceiro local (NO II), afastado 35Km da fonte emissora e na primeira direção dos ventos foi analisado partículas inaláveis grossas (MP10). Extratos orgânicos foram obtidos dos filtros com solvente diclorometano e avaliados pelo ensaio Salmonella/microssoma, método de microssuspensão, com as linhagens TA98, YG1021 e YG1024. Para avaliar a mutagenicidade dos metabólitos utilizou-se a fração de metabolização de mamíferos (S9). Também foram empregados Ensaio Cometa (EC) e Teste de Micronúcleos em linhagem celular de pulmão de hamster chinês (V79), nos extratos dos locais NO e NE. Os 16 hidrocarbonetos políclicos aromáticos (HPAs) considerados preferenciais pela agência ambiental norte americana (USEPA) foram avaliados nos extratos orgânicos para caracterização dos três locais. Foi realizado o biomonitoramento humano em crianças de escolas públicas do Local NO e NO II, com coleta de sangue periférico e células esfoliadas da mucosa oral. Em sangue periférico foi utilizado o Ensaio do micronúcleo (MN) com bloqueio da citocinese- citoma (CBMN-cyt) para avaliar as frequências de células com MN e anomalias nucleares (brotos nucleares - NBUDs, pontes nucleoplásmicas -NPBs), e EC avaliando o parâmetro intensidade de cauda. Utilizou-se o Ensaio do MN em mucosa oral-citoma (BMCyt) para detectar MN e anomalias nucleares. Todos os extratos de MP2,5 mostraram mutagenicidade pelo ensaio Salmonella, sendo destacada a presença de compostos nitrogenados. Verificaram-se respostas genotóxicas no EC em 87% dos extratos testados e indução de micronúcleos em 74% dos ensaios realizados, além de citotoxicidade em V79, para todas as amostras avaliadas. Os resultados obtidos nos três biomarcadores in vitro, e o perfil de HPAs mais tóxicos no material particulado, apontaram pior qualidade do ar do Local NO, sendo compatível com a maior dispersão de poluentes na primeira direção dos ventos. O biomonitoramento contou com a participação de 54 crianças de 5 a 12 anos, com média de 8,3 ± 1,8 anos. Danos ao DNA pelo EC foram significativamente mais elevados no local NO, em relação ao local NO II. A frequência de MN no CBMN-cyt não diferiu entre os grupos, porém, foram significantemente maiores em relação a um local de referência externo. A ocorrência de NBUDs foi significativamente mais elevada no local NO II. Quanto ao ensaio BMCyt, não houve diferença entre os grupos para MNs e NBUDs. As frequências das alterações nucleares, cariorréxis e cariólise, foram significativamente mais elevadas no local mais afastado da fonte emissora (NOII). A avaliação ambiental associando o Ensaio Salmonella e análise de HPAs mostrou que mesmo amostras dentro dos padrões de controle da qualidade, apresentam potencial genotóxico. Estes resultados permitiram evidenciar que as crianças avaliadas estão expostas a uma mistura de contaminantes de diferentes fontes, sendo a proximidade da indústria petroquímica um contribuinte aos fatores de risco. Medidas são necessárias para identificar e reduzir emissões e efeitos perigosos, uma vez que os padrões de qualidade do ar não são suficientes para garantir a saúde das populações expostas. A complexa composição do MP2,5 pode provocar diversos efeitos genotóxicos, sendo a utilização de diferentes bioensaios fundamental para o entendimento dos efeitos dessa matriz. / Good air quality is essential key to human and environmental health maintenance. Atmospheric particulate matter is an air pollutant consisting of a variety of organic and inorganic substances, some of which presents genotoxic characteristics. The petrochemical industry is an important activity in Rio Grande do Sul state, Brazil, with a history of emissions that are detrimental to air quality. The present study aimed to evaluate the biological effects associated with the dispersion of inhalable particulate matter in an area under the influence of a petrochemical complex, integrating the results of environmental and human biomonitoring through genotoxicity biomarkers. Particulate matter samples were collected in mixed rural, urban and industrial area, using Teflon membrane filters and large air volume samplers, weekly, for periods of 24 hours. Fine inhalable particles (PM2.5) were sampled at two locations - NO and NE - positioned in the first and second preferential wind directions in the study region, 2.5 km away from the main emission source of industrial raw material center. In a third location (NO II), 35 km away from the emission source and in the first wind direction, coarse inhalable particles (MP10) were analyzed. Organic extracts were obtained with dichloromethane from sampled filters and evaluated by the Salmonella/microsome assay, microsuspension method, with the strains TA98, YG1021 and YG1024. The mammalian metabolization fraction (S9) was used to evaluate metabolite mutagenicity. Also, the Comet Assay (EC) and Micronucleus Test in Chinese hamster lung cell line (V79) was used to test the NO and NE samples. The 16 polycyclic aromatic hydrocarbons (PAHs) considered preferential by the US Environmental Agency (USEPA) were evaluated in the organic extracts for characterization of the three sites. Human biomonitoring was carried out in children of public schools from NO and NO II sites, through the collection of peripheral blood and buccal exfoliated cells. To peripheral blood samples, the cytokinesis-block MN cytome assay (CBMN-cyt) was used to evaluate the frequencies of cells with micronuclei (MN) and nuclear abnormalities (nuclear buds - NBUDs, nucleoplasmic bridges - NPBs), and EC evaluating the tail intensity. The buccal MN cytome assay (BMCyt) was used to detect MN and nuclear abnormalities. All PM2.5 extracts showed mutagenicity through the Salmonella assay, highlighting the nitrogenated compounds effects. Genotoxic responses in EC were observed in 87% of the tested extracts and MN induction in 74% of the tests, in addition all the samples showed cytotoxicity to V79 cells. The results of the three biomarkers in vitro and the more toxic PAHs profile presented by the particulate matter, showed a lower air quality of NO site. It is compatible with the greater pollutants dispersion in the first winds direction. Biomonitoring included 54 school children aged 5 to 12 years, with a mean of 8.3 ± 1.82 years. DNA damage evaluated by EC was significantly higher in children from NO compared to NO II. The MN frequency by CBMN-cyt did not differ between groups, however, it was significantly higher in relation to an external reference site. The occurrence of nuclear buds was higher at the NO II site. Regarding the BMCyt assay, there was no difference between groups for MNs and NBUDs. The frequencies of nuclear abnormalities, karyorrhexis and karyolysis were significantly higher at the site farthest from the emission source (NOII). The environmental evaluation with the Salmonella assay and PAH analysis showed genotoxic potential even to samples within the quality standards. These results showed that the schoolchildren are exposed to a mixture of contaminants from different sources, being the proximity of the petrochemical industry a risk factor. Actions are needed to identify and reduce emissions and adverse effects since air quality standards are not enough to ensure the health of exposed populations. The complex PM2.5 composition could cause several genotoxic effects, and the use of different bioassays is fundamental for understanding the effects of this environmental matrix.

Orientador: José Paes de Almeida Nogueira Pinto / Resumo: O presente trabalho avaliou 250 animais de 25 lotes distintos abatidos em 4 estabelecimentos do estado de São Paulo para a presença de Salmonella nos linfonodos mesentéricos, e caracterizou o perfil de resistência das cepas isoladas aos principais antibióticos. O patógeno estava presente em 36,4% das amostras e 72% dos lotes analisados. Dos 91 isolados, 67 foram sorotipados, e os principais sorovares encontrados foram S. Typhimurium (n=13), S. 1.4,5,12:i:- (n=12) S. Infantis (n=12) e S. Havana (n=11). Os compostos com menor eficácia frente aos isolados foram estreptomicina e tetraciclina (68,1% de resistência) ampicilina e sulfonamidas (62,6%), cloranfenicol (56,0%), trimetoprim-sulfametoxazol (41,8%) e ácido nalidíxico (40,7%). Os mais efetivos foram aztreonam e cefoxitina, (ambos com 3,3% de resistência) e cefepima e ceftriaxona, (ambos com 7,7%). Cepas multidrogas resistentes (MDR) corresponderam a 70,3% dos isolados. Oito cepas foram submetidas ao MLST: quatro S. Typhimurium e uma S. 1.4,5,12:i:- todas pertencentes ao ST 19, duas S. Infantis pertenceram ao ST 32 e uma S. Derby, pertencente ao ST 40. A grande prevalência do patógeno nos animais analisados, com altas taxas de resistência aos antibióticos e pertencentes a grupos genéticos frequentemente associados a surtos e doenças em humanos demonstram que a cadeia produtiva da carne suína é uma fonte de contaminação em potencial nos casos de salmonelose, sendo necessárias medidas preventivas eficazes para o controle do pa... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This study evaluated 250 animals of 25 different batches processed in four slaughterhouses in São Paulo state - Brazil for the presence of Salmonella in the mesenteric lymph nodes, and characterized the resistance profile for the main antibiotics. The pathogen was present in 36.4% of samples and 72% of the analyzed batches. Of the 91 isolates, 67 were serotyped, and the main serovars found were S. Typhimurium (n = 13), S. 1.4,5,12:i- (n = 12) S. Infantis (n = 12) and S. Havana (n = 11). The compounds with less efficacy were streptomycin and tetracycline (68.1% resistant) ampicillin and sulphonamides (62.6%), chloramphenicol (56.0%), trimethoprim-sulfamethoxazole (41.8%), and nalidixic acid (40.7%). The most effective were cephalothin and aztreonam, (both with 3.3% resistant) and ceftriaxone and cefepime (both with 7.7%). Multidrug-resistant strains (MDR) accounted for 70.3% of the isolates. Eight strains were submitted to MLST: Four S. Typhimurium and one S.1.4,5,12:i:- all belonging to the ST 19, two S. Infantis, belonging to the ST 32 and one S. Derby, belonging to ST 40. The high prevalence of the pathogen in the analyzed animals, with high rates of resistance to antibiotics and belonging to genetic groups that are often associated with outbreaks and disease in humans, shows that the production chain of pork is a potential source of contamination in salmonellosis cases, with the necessity of effective preventive measures for pathogen control and lower the risk of foodborne... (Complete abstract click electronic access below) / Mestre

Corrigenda attached after the bibliography. Bibliography: leaves 166-206.

Files on accompanying CD-ROM: Appendix III Phages ST64T and ST64B sequences, are in rtf format. Bibliography: leaves 279-324. System requirements for accompanying CD-ROM: IBM or compatible ; Microsoft Word or compatible to read rtf files.

Corrigenda attached after the bibliography. / Bibliography: leaves 166-206. / 206 leaves [6] leaves of plates : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Molecular Sciences, 2001