Thesis (M.S.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains iii, 50 p. : ill. (some col.). Includes abstract. Includes bibliographical references.

Thesis (Ph. D.)--University of Rhode Island, 2004. / Typescript. Includes bibliographical references (leaves 104-116).

Thesis (Ph. D., Microbiology, Molecular Biology and Biochemistry)--University of Idaho, August 2009. / Major professor: Carolyn H. Bohach. Includes bibliographical references. Also available online (PDF file) by subscription or by purchasing the individual file.

Thesis (M.S.)--Tennessee Technological University, 2009. / Title from title page screen (viewed on Aug. 26, 2009). Bibliography: leaves 40-45.

The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on Oct. 7, 2009). Thesis advisor: Dr. Azlin Mustapha. Includes bibliographical references.

Thesis (M.S.)--Ball State University, 2009. / Title from PDF t.p. (viewed on June 07, 2010). Includes bibliographical references.

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Made available in DSpace on 2014-06-11T19:27:23Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-11-30Bitstream added on 2014-06-13T18:56:07Z : No. of bitstreams: 1 prata_cb_me_jabo.pdf: 1292020 bytes, checksum: 1886044e5ddc4f62eed48d5f34981c8d (MD5) / Universidade Estadual Paulista (UNESP) / Escherichia coli O157:H7 é uma cepa de importância crescente por estar associada a vários surtos graves de doença em humanos, a maioria derivada do consumo de carne bovina crua ou mal cozida. Os bovinos constituem seu reservatório mais importante, aventando-se a hipótese de que mudanças do regime alimentar em confinamentos atuariam favoravelmente ao aparecimento de cepas shigatoxigênicas. Neste estudo objetivou-se verificar, comparativamente durante o abate, a prevalência desse sorotipo e o comportamento de métodos indicadores como a contagem total de microrganismos viáveis (CTMV) e de contaminação fecal - coliformes totais e E. coli, em amostras de fezes e em carcaças de bovinos terminados a pasto e em confinamento, possibilitando a disponibilização de subsídios necessários aos programas de Análise de Perigos e Pontos Críticos de Controle (APPCC) e de Análise de Risco (RA), empregados na redução do risco de doenças transmitidas por alimentos. Identificados os lotes de acordo com a terminação (dez de cada tipo), desses foram aleatoriamente colhidas e analisadas 100 amostras de suabe retal, 100 amostras de carcaças e 67 amostras de “recortes” da desossa (carne industrial) utilizando-se, para a E. coli O157- H7, técnica automatizada de PCR. À exceção de uma única amostra de recortes (0,37%), as demais, tanto de fezes quanto de carcaças, foram negativas para a cepa pesquisada. Além de contatar-se uma prevalência muito baixa, não se evidenciou diferenças entre os tipos de terminação dos animais. Os resultados dos indicadores - CTMV, de coliformes totais e E. coli, foram considerados aceitáveis em 91%, 85% e 93% das amostras, respectivamente, oferecendo suporte e concordância com a baixa prevalência encontrada. / Escherichia coli O157:H7 is an important strain that has been associated with outbreaks of serious disease in humans, most being derived from consumption of raw or poorly cooked beef. It is likely that cattle are an important reservoir, suggesting the possibility that changes in feedlot diet favor the emergence of shigatoxigenic strains of E. coli. This study is intended to verify, comparatively during bovine slaughter, the occurrence of E. coli O157:H7 associated with the sampling results obtained by means of general indicator methods (total viable count) and fecal contamination indicators (coliforms and E. coli). Samples will be taken from both excreta and carcasses of cattle finished either on pasture or feedlot, allowing the provision of subsidies necessary for Hazard Analysis and Critical Control Points (HACCP) and Risk Analysis (RA) programs and applied in the reduction of the risk of foodborne diseases. After identification of batches according to the type of finishing (feedlot or pasture), samples were randomly collected and analyzed. 100 rectal swabs, 100 samples from carcasses sponging, and 67 samples of sliced meat from the boning room (industrial meat). An automatic PCR technique for detection of E. coli O157:H7 was used. Except for one sample of sliced meat (0.37%), all others, both for excreta and carcasses, were negative for the O157:H7 E. coli strain. There were no significant differences in prevalence between the types of cattle finishing of the animals. The results of the indicators methods (TVC, coliforms and E. coli); were considered acceptable in 91%, 85% and 93% of tested samples, respectively, supporting and in agreement with low prevalence of O157:H7 found.

Master of Science / Department of Clinical Sciences / Michael W. Sanderson / Escherichia coli O157:H7 has emerged as a significant human food-borne pathogen over the past two decades. While cattle have been identified as the major reservoir of the pathogen, the dynamics of shedding are still largely unknown. The role immunosuppression may play on fecal shedding in cattle is explored. The first study determined whether immunosuppression induced by dexamethasone injections affects the level and duration of fecal shedding of E. coli O157. Six one week old Holstein bull calves were injected intramuscularly with dexamethasone and orally inoculated with 109 CFU of a mixture of three nalidixic-acid resistant strains of E. coli O157. Another five one week old Holstein bull calves, only inoculated with the E. coli O157, served as controls. All calves were necropsied and samples from the gastrointestinal tract were cultured. Dexamethasone treated calves shed at higher levels on days four and seven post-inoculation, but not thereafter. The data from this study suggest that there may be a time dependent correlation between dexamethasone immunosuppression and the concentration of E. coli O157 an animal will shed in the feces and that transient immunosuppression does not result in prolonged shedding of E. coli O157. The goal of the second study was to determine whether calves immunosuppressed by persistent infection with bovine viral diarrhea virus (BVDV) will shed E. coli O157 at a higher level and for a longer duration than a normal animal. Nine six to eight week old calves persistently infected with non-cytopathic BVDV and eight normal calves obtained from separate cow-calf operations were orally inoculated with 109 CFU of a mixture five nalidixic-acid resistant strains of E. coli O157. All calves were necropsied and samples from the gastrointestinal tract cultured. There was no statistical difference in the concentration of E. coli O157 shed or the duration of shedding between the persistently infected BVDV calves and the control calves throughout the length of the study. The data suggest that immunosuppression caused by persistent infection with non-cytopathic BVDV infection does not play a role in the level or duration of shedding of E. coli O157:H7 in calves.

Detecta la presencia y determina la prevalencia de E. coli O157:H7 en Latuca sativa (lechuga) y Spinacea oleracea (espinaca), obtenidas de fundos agrícolas de la periferia de la ciudad de Lima. Se analizan 120 muestras de hortalizas, proveniente de 4 fundos de Lima; se utiliza la técnica del número más probable para la enumeración de E. coli, para la caracterización de E. coli O157:H7 se emplea el enriquecimiento selectivo, el análisis bioquímico y pruebas serológicas. Para determinar la presencia de los factores de virulencia shigatoxina (stx) e intimina (eaeA) se emplea el método de PCR en tiempo real. Para la entero hemolisina se realiza la prueba de hemólisis. Del total de muestras recolectadas (120), el 13,33 %(16) resulta positivo para E. coli O157:H7, el 1,67 %(2) presenta E. coli O157 no H7. De las 16 cepas (13,33 %) de E. coli O157:H7 se obtienen las siguientes secuencias de factores de virulencia: 3 (2.50 %) stx - / eaeA + y Hem - ; 8 (6,65 %) stx +/ eaeA + y Hem -; 2 (1,67 %) stx + / eaeA + y Hem +; 2 (1,67 %) stx + / eaeA - y Hem -; y 1 (0,83 %) stx - / eaeA + y Hem +. Así mismo el 86,67 % resulta negativo para E. coli O157:H7. El estudio revela la presencia de E. coli O157:H7 con una prevalencia del 13,33 % en hortalizas de fundos agrícolas de la periferia de la ciudad de Lima. / Tesis