Preparo e avaliação de material de referência para análise de Salmonella

• Ano de defesa: 2008
• Autor(a) principal: Silva, Carolina dos Santos Fernandes da
• Orientador(a): Vanetti, Maria Cristina Dantas
• Banca de defesa: Pinto, Cláudia Lúcia de Oliveira , Mizubuti, Eduardo Seiti Gomide
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Mestrado em Microbiologia Agrícola
• Departamento: Associações micorrízicas; Bactérias láticas e probióticos; Biologia molecular de fungos de interesse
• País: BR
• Palavras-chave em Português: Material de referência; Salmonella; PCR; Imunoanálise; Método convencional; Qualidade; Alimentos
• Palavras-chave em Inglês: Reference material; Salmonella; PCR; Immunoanalysis; Conventional method; Quality; Food
• Área do conhecimento CNPq: CNPQ::CIENCIAS AGRARIAS::CIENCIA E TECNOLOGIA DE ALIMENTOS::TECNOLOGIA DE ALIMENTOS
• Link de acesso: http://locus.ufv.br/handle/123456789/5336

The use of Reference Material (RM) in microbiological food analyses increased around the world, mainly with the introduction of quality control and management programs in laboratories. The necessity of the standardization of analysis methods makes the demand for this type of material increase which allows the determination of precision and repeatability of the experimental data. This study aimed to prepare microbiological RMs for quantitative and qualitative analyses of Salmonella, to evaluate the homogeneity and stability of the material during storage time and to compare the sensitivity of the Salmonella detection methods. The study was performed in two stages. The first with RM containing approximately 103 CFU/ g of Salmonella cells, submitted or not to starvation and storage conditions, up until 240 days, at -20 °C. The second stage consisted of the RM preparation containing approximately 10 CFU/ g for comparison of the methodology sensibility of Salmonella detection in food. The RM homogeneity and stability containing approximately 103 CFU/ g was evaluated through the T1 statistical test, analysis of linear regression and proficiency test, while the RM performed with a low number of Salmonella cells was evaluated by the T2 statistical test and by the Epiinfo program of the Center for Disease Control (CDC) of the USA for the evaluation of the detection methods of Salmonella in this material. The T1 statistical test for the RM prepared with 103 CFU/ g demonstrated superior values to the recommended ones for this type of material, which indicated the necessity for new studies for the improvement of the Salmonella resistance to the dehydration and storage conditions. However, the same material presented itself homogeneous in the proficiency test performed by three different laboratories, when the σp value was obtained until 25 % as recommended by the Food Examination Performance Assessment Scheme (FEPAS) of the United Kingdom. In the linear regression analysis, no significant difference was noted between the RMs produced with and without stressed cells, in spite of the decline tendency of the number of Salmonella cells in the material made without stressed cells being obvious after 240 storage days at -20 °C. For the RM prepared with 10 CFU/ g, the T2 statistical test presented acceptable results, after 60 storage days at 4 °C. One gram servings of this RM were evaluated by three analytical methodologies which included the conventional method, the immunoanalytical method VIDAS® and automated PCR, by the BAX system. The results were consistent in all the analyzed samples in the first two methods, with a Kappa rate equal to 1. The PCR method presented an agreement in approximately 95 % to the conventional methodology, with a Kappa rate equal to 0.64. False-negative results were observed in 5% of the analyzed samples, when the PCR method was used. However, this result does not compromise the technique sensibility. This study demonstrated advantages of the quick methodology use of Salmonella detection in food, which offers, besides greater speed and practicality forgetting results, similar sensitivity to the conventional method recommended by Brazil´s Ministry of Agriculture.