Escherichia coli O157:H7: ocorrência em ambiente de produção de leite na microrregião de Viçosa, adesão em diferentes superfícies e resistência a sanitizantes

• Ano de defesa: 2008
• Autor(a) principal: Morelli, Ana Márcia de Faria
• Orientador(a): Mendonça, Regina Célia Santos
• Banca de defesa: Andrade, Nélio José de , Peña, Wilmer Edgard Luera , Pinto, Cláudia Lúcia de Oliveira
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Doutorado em Ciência e Tecnologia de Alimentos
• Departamento: Ciência de Alimentos; Tecnologia de Alimentos; Engenharia de Alimentos
• País: BR
• Palavras-chave em Português: Escherichia coli O157:H7; Sanitizantes; Biofilme
• Palavras-chave em Inglês: Escherichia coli O157:H7; Sanitizing products; Biofilm
• Área do conhecimento CNPq: CNPQ::CIENCIAS AGRARIAS::CIENCIA E TECNOLOGIA DE ALIMENTOS::CIENCIA DE ALIMENTOS
• Link de acesso: http://locus.ufv.br/handle/123456789/401

The microbiological quality of raw milk has been given great attention due to the high count of mesophilic anaerobics and coliforms, which indicate contamination during processing and storing. Coliforms may also produce enzymes that compromise the quality of dairy products of which the raw milk is destined for. The scope of this work was to study the possibility of Escherichia coli O157 occurrence in the area where milk that supplies Viçosa is produced, isolate thermotolerant coliforms and E. coli O157 strains from rural properties where dairy cattle is raised, evaluate the adhesion of E. coli O157:H7 ATCC 43895 by means of the standard plate count (SPC) on several surfaces used in food processing units, evaluate and mathematically model the E. coli O157:H7 (ATCC 43895) biofilms formations on different surfaces by implementing a central composite rotational design applicable to the responses of temperature exposition and incubation time, and evaluate the E. coli O157:H7 (ATCC 43895) resistance to the sanitizing products which are largely used in the disinfection of industrial food processing equipments and appliances as well as in industrial restaurants and kitchens. Thermotolerants coliforms count for raw milk samples was between < 0,3 and 21 NMP.mL-1. Twenty-nine (36,3 %) from the analyzed samples showed contamination. A count varying from < 0,03 and > 11,0 NMP.mL-1 of thermotolerant coliforms was achieved for water. That indicates a potential danger of pathogens introduction in the milk through udder, appliances and equipments contamination. Fifteen strains of E. coli were isolated; however, such strains did not show to belong to the serotyping O157. The incidence of coliforms and E. coli in raw milk has been given considerate attention due to its association to fecal contamination and the following risk of other fecal pathogen presence. In the evaluation of E. coli O157:H7 ATCC 43895 adhesion by means of the standard plate count (SPC) on several surfaces used in food processing units, it was observed an increase in the adhesion in function of the contact time to all evaluated surfaces. Lower adhesion occurred to the stainless steel and higher adhesion to PVCRF after 10-hour contact. According to the Scott-Knott test, there was no meaningful difference in the microorganism adhesion (p > 0,05) only for the stainless steel at 2 and 4 hour contact. There was meaningful differences on the adhesion intensity to all the evaluated surfaces for contact periods equals or higher then 6 hours. Meaningful differences (p < 0.05) to the microorganism adhesion when each surface was evaluated through different contact periods were shown. The stainless steel surface when analyzed under the microscope revealed microtopographic characteristics very different from the other surfaces, what may justify the differences among the adhesion rates found in this experiment. It was shown by means of the central composite rotational design implementation that the achieved models for the three surfaces were validated, once the predictions for all results were higher than the values found in the experiment, that is, predictions tended to the safer side where the predicted adhesion rates were higher to the real ones. The results achieved for E. coli O157:H7 ATCC 43895 resistance to the most used sanitizing products showed a variation on the efficiency based on decimal reductions in the antimicrobial effect performed by the different sanitizing products that were evaluated. Following the AOAC test, 30 seconds is adopted as the contact period between the microorganism and the sanitizing product being tested. According to these criteria, the sanitizing products sodium hypochlorite at 100 and 200 mg.L-1, sodium dichloroisocyanurate at 200 mg.L-1, 2 % hydrogen peroxide, peracetic acid at 30 mg.L-1, grapefruit seed extract at 1:1500 and 0.20 % quaternary ammonia answered the specifications. The results showed the importance of proper hygiene practices in the food industry. Thus, it is suggested to evaluate such hygiene procedures and the use of sanitizing agents which are the most adequate to the surfaces used in the food processing industries.