Enterotoxigenicidade de Staphylococcus aureus isolados de queijo Minas Artesanal da Canastra

• Autor(a) principal: Dores, Milene Therezinha das
• Data de Publicação: 2013
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/424
• topic: Serra da Canastra; PCR; Sensibilidade ótima em placas; Canastra; PCR; Optimal Sensitivity plates; CNPQ::CIENCIAS AGRARIAS::CIENCIA E TECNOLOGIA DE ALIMENTOS::CIENCIA DE ALIMENTOS

The Minas artisanal cheese is, for centuries, the only link small producers with the market, so it is what gives them survival. Previous studies have shown that cheese Minas artisanal S. aureus is the species that define the minimum time needed to obtain ripening microbiological safety, since, in high counts remained for a long period during ripening. Considering that the presence of S. aureus is common in this type of cheese, the present study aimed to evaluate the presence of S. aureus enterotoxigenic endogenous starter in Minas artisanal cheeses and the Serra da Canastra. We collected 16 samples of endogenous starter and cheese in two seasons, rainy and dry. The counting and the isolation of S. aureus were performed on plate count PetrifilmTM - Rapids S. aureus. For detection of enterotoxins in cheese it was used the method in Optimal Sensitivity plates (OSP) for enterotoxinas SEA, SEB, SEC and SED and methods ELFA-VIDAS® Staph enterotoxina II for enterotoxins SEA, SEB, SEC1,2,3, SED and SEE. Strains S. aureus were tested for their ability to produce enterotoxins, using the OSP and by PCR analysis for the classical enterotoxin genes. The counts of S. aureus in cheese ripening eight days were above the limit required by Brazilian law -2.0 log CFU g-1, and ranged from 3.48 to 5.88 log CFU g-1 for rainy season and from 3.11 to 4.60 log CFU g-1 for the period of drought. Since counts of S. aureus in endogenous leaven were lower, ranging from <1 to 3.11 log CFU g-1. Only the enterotoxin SEA was detected by the OSP method, being present in 75% of samples of cheese. No toxin was detected with the method ELFA-VIDAS however false negative results were found, which may be due to the presence of possible interferences, such as substances not related to immune matrix. It was observed that 12.5% of the strains isolated produced SEA and SEC. When using the PCR assay, one isolate showed enterotoxin gene. When using the PCR assay, only two isolates enterotoxin genes (seb e seg). Although the results of the immunological and molecular methodology have been contradictory, S. aureus strains isolated from the endogenous starter and QMA showed low potential enterotoxinogênico. However, the findings in this study highlight the need for further studies to develop analytical methods that do not show interference in the results and include also the non-classical enterotoxins.