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| Author(s): |
Giovana Verginia Barancelli
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Pirassununga. |
| Institution: | Universidade de São Paulo (USP). Faculdade de Zootecnica e Engenharia de Alimentos (FZE/BT) |
| Defense date: | 2010-12-09 |
| Examining board members: |
Carlos Augusto Fernandes de Oliveira;
Juliana Pfrimer Falcão;
Eliana Setsuko Kamimura;
Arnaldo Yoshiteru Kuaye;
Marta Mitsui Kushida
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| Advisor: | Carlos Augusto Fernandes de Oliveira; Ernani Porto |
| Abstract | |
Listeria monocytogenes surveys in cheese manufacturing plants in Brazil are rare. Three cheese manufacturing plants (A, B and C) in São Paulo state were monitored for the presence of Listeria monocytogenes during the period of October/2008 - September/2009. Twelve samples surveys were taken corresponding to 12 cheese lots produced, four in each plant. In each cheese plant, the samples were taken at intervals of approximately 2 months. There were 393 samples analyzed, 201 from surfaces with and without contact with food and 192 of food (raw and pasteurized milk and cheese), water and brine, with the objective of searching for L. monocytogenes. The analyses were performed in accordance with Food and Drug Administration (FDA) method. The results confirmed the presence of Listeria spp in the facilities of three plants. L. monocytogenes, L. innocua, L. seeligeri and L. weshimeri were the species isolated in this study. Specifically the L. monocytogenes specie was not isolated from plant A. However, the microorganism was isolated in 12.5% of the samples from plant B and 9.1% from plant C. Listeria monocytogenes was not isolated from raw milk in storage tanks, pasteurized milk, water or Minas frescal cheese samples from the three plants. Nevertheless, in plant C, L. monocytogenes was isolated in Prato cheese that was included only in the 4th sampling survey and also from the brine samples. The major prevalence of contamination by L. monocytogenes occurred on surfaces without contact with food, with 51.6% of the samples positive from plant B and 21.7% from plant C. In both plants, the microorganism was also isolated from food contact surfaces. The results provide detailed information about the critical points for the development of L. monocytogenes control strategies in cheese processing plants and, moreover, show the relevance of sampling programs of the pathogen, even in small cheese processing plants. The 85 isolates identified as L. monocytogenes were classified in four serotypes: 1/2a, 1/2b, 1/2c and 4b, with 4b dominating in both cheese plants, which is of concern to human health. On the basis of PFGE results (combined profiles ApaI and AscI), 40 profiles (pulsotypes) were found. Pulsotypes were isolated repeatedly among sampling surveys in plants B and C, suggesting persistence of lineages in the plants. Despite these plants being distant and independent, one pulsotype was shared between them. Plant A presented contamination by more than one pulsotype of L. seeligeri and there was a repetitive isolation of one pulsotype of this specie among samplings, suggesting adaptation of the bacterium and the need for control of the Listeria genus in this plant. The occurrence of one single pulsotype of L. monocytogenes with different serotypes (1/2b and 4b) show that serotyping should follow more refined analyses as the ones of genotypic nature. (AU) | |