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Incidence de paramètres technologiques sur l'expression de gènes et la production d'entérotoxines de Staphylococcus aureus au cours des 72 h suivant l'empresurage des laits en fabrication fromagère

Abstract : In France, Staphylococcus aureus is reported to be the most frequent pathogen involved in food-borne diseases associated with milk and dairy products. Food poisoning results from ingestion of staphylococcal enterotoxins (SE) preformed in food by enterotoxigenic strains of S. aureus. In order to identify key technological parameters affecting S. aureus growth, enterotoxin gene expression and enterotoxin production during uncooked semi-hard cheese manufacturing, the impact of varying certain process parameters was studied with various experimental designs. To study enterotoxin gene expression during cheese manufacture, we first developed an efficient procedure to recover total RNA from cheese and applied a robust strategy to study gene expression by quantitative RT-PCR. Based on a survey of practices performed amongst uncooked semi-hard cheese manufacturers, we studied the impact of five technological parameters of the cheese-making process on the behavior of five enterotoxigenic strains producing enterotoxin A, B, C or D and independently inoculated at 10³ cfu/ml in milk, during the first 72 h of the manufacturing. Whatever the parameters and the strains tested, the S. aureus population was found to exceed 10⁵ cfu/g of cheese four hours after molding. In the 54 different cheese productions, SEA and SED were the only enterotoxins detected, and in very low (non measurable for SEA) and variable quantities depending on the parameters studied. Enterotoxin production seems to be correlated with an early gene expression during cheese processing (less than 6 hours after milk renneting). The first experimental design carried out highlighted that among the five parameters studied, temperature and duration of milk maturation had the biggest impact on the SE production. Using response surface methodology, we established mathematical models to describe the relationship between staphylococcal enterotoxin gene expression and production and both milk maturation parameters. Milk maturation temperature was demonstrated to be the key technological parameter that must be fixed to limit the risk of staphylococcal food poisoning.
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https://pastel.archives-ouvertes.fr/pastel-00569982
Contributor : Agnès Grimal <>
Submitted on : Friday, February 25, 2011 - 5:16:17 PM
Last modification on : Friday, October 23, 2020 - 4:38:15 PM
Long-term archiving on: : Saturday, December 3, 2016 - 10:55:45 PM

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  • HAL Id : pastel-00569982, version 1
  • PRODINRA : 246656

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Citation

Manon Duquenne. Incidence de paramètres technologiques sur l'expression de gènes et la production d'entérotoxines de Staphylococcus aureus au cours des 72 h suivant l'empresurage des laits en fabrication fromagère. Ingénierie des aliments. AgroParisTech, 2010. Français. ⟨NNT : 2010AGPT0015⟩. ⟨pastel-00569982⟩

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