The purpose of this study was to determine the viability of Mycobacterium avium subsp. paratuberculosis (MAP), Escherichia coli (E. coli), and Salmonella Enteritidis (S. Enteritidis) during preparation and refrigerated storage of yogurt. Three yogurts were prepared using pasteurized commercial milk. Each yogurt was artificially contaminated with (1) MAP, (2) E. coli + S. Enteritidis, and (3) MAP + E. coli + S. Enteritidis. Samples were taken during and after the fermentation process until day 20 after inoculation. MAP was not detected during their preparation and short-term storage but was recuperated after starting at 180？min after inoculation storage. Live bacterial counts of E. coli, and S. Enteritidis increased during the first 24 hours, followed by a slight decrease towards the end of the study. In this study it was shown how MAP, E. coli, and S. Enteritidis resisted the acidic conditions generated during the preparation of yogurt and low storage temperatures. This work contributes to current knowledge regarding survival of MAP, E. coli, and S. Enteritidis during preparation and refrigerated storage of yogurt and emphasizes the need to improve hygiene measures to ensure the absence of these pathogenic microorganisms in dairy products. 1. Introduction Mycobacterium avium subsp. paratuberculosis (MAP) is the causative agent of paratuberculosis or Johne’s disease. MAP affects domestic and wild animals and, in cows, causes chronic enteritis, diarrhea, weight loss, and progressive emaciation that can eventually lead to death [1]. MAP has also been linked to human Crohn’s disease, a systemic disorder that causes mainly a chronic inflammation of the intestine [2]. It is suggested that humans might be infected through contaminated milk, although relatively little is known about MAP survival during industrial milk manipulation. Some authors have suggested that pasteurization is capable of destroying mycobacteria. Thus, laboratory assays were performed to evaluate MAP heat resistance according to differential distribution of heat treatment during pasteurization [3–6]. In contrast, other authors support the theory that MAP is able to resist pasteurization when it is present in raw milk [7–13]. Viable MAP was detected in commercial pasteurized milk in the UK, the USA, the Czech Republic, and India [10, 11, 14–16]. Furthermore, in the Czech Republic, using F-57 or IS900 real-time PCR, MAP was detected in 49% of samples of powdered infant milk, with one study yielding viable MAP [17]. Nevertheless, little was published regarding MAP in dairy products other than
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