Survival of Mycobacterium avium ssp. paratuberculosis in yoghurt and in commercial fermented milk products containing probiotic cultures

Abstract

Aims: To assess the survival of Mycobacterium avium ssp. paratuberculosis (MAP) in yoghurt and commercial fermented milk products containing probiotic strains. Methods and Results: Whole and skimmed UHT milk artificially inoculated with MAP were used to manufacture yoghurt, using two different yoghurt starter cultures. Five commercial fermented milk products were inoculated with MAP. Two different MAP strains were studied. The survival of MAP in all products was monitored by culture over a 6‐week storage period at 6°C. In yoghurt, MAP counts did not change appreciably during the storage period. Fat content and type of yoghurt starter culture had no consistent effect on the survival of MAP. In the fermented milk products, survival patterns varied but resulted in a 1·5 to ≥3·8 log reduction for the Niebüll strain and a 1·2–2·2 log reduction for the NIZO strain after 6 weeks, depending on the probiotic starters present in the product. Conclusions: MAP easily survived in yoghurt but MAP numbers decreased in fermented milk products containing probiotic cultures. Significance and Impact of the Study: The results contribute to the lack of knowledge on the behaviour of MAP in yoghurt and fermented milk products containing probiotic cultures. This knowledge is valuable in the context of the risk of MAP transmission to humans via yoghurt and the possible contribution of probiotic fermented milk products to the elimination of MAP.

Identification and Characterization of a Spore-Like Morphotype in Chronically Starved Mycobacterium avium Subsp. Paratuberculosis Cultures

“…These colonies were also positive for MAP- specific IS900 (Figure 5d). MAP spore survival post exposure to 70°C may in fact not be extremely surprising since many studies have shown the presence of MAP as a food contaminant in pasteurized (also treated at 70°C) milk, cheeses and yogurt [40], [41], [42], [43]. It is currently unknown if the MAP found in these dairy products may exist in a spore or spore-like state.…”

Growth ofMycobacterium aviumsubsp.paratuberculosis,Escherichia coli, andSalmonellaEnteritidis during Preparation and Storage of Yogurt

“…If indeed MAP is present in pasteurized milk, it might be transferred to humans upon consumption of by-products. Therefore, it is interesting to gain insights into the behavior of MAP in such products as the acidic nature of yogurt (pH about 4–4.5) generally contributes to the inactivation of bacterial pathogens [18]. …”

“…In all samples, MAP counts were low due to the aggressive step of decontamination. van Brandt et al [18] found that initial MAP counts remain unchanged over the 6 weeks of refrigerated storage, regardless of starter culture used and the fat content of milk, but did not evaluate its isolation during preparation. Sung and Collins [29] found that at low pH levels in vitro , MAP expressed two proteins related at the acid tolerance.…”

“…In general, fermented milk products provide significant barriers to pathogen's growth, starting with heat treatment during pasteurization, followed by the addition of a starter culture and the acidity environment during fermentation as well as refrigerated storage. van Brandt et al inoculated MAP into ultrahigh temperature (UHT) milk and observed that initial MAP counts, during yogurt fermentation followed by storage at 6°C, remained unchanged for over 6 weeks, regardless of the starter culture that was used or the fat content of milk [18]. …”

A murine oral model for Mycobacterium avium subsp. paratuberculosis infection and immunomodulation with Lactobacillus casei ATCC 334

“…Because M. paratuberculosis is a worldwide problem in cattle and a suspected agent for human Crohn's disease (Hermon-Taylor and Bull, 2002; Divangahi et al, 2008), alternative treatment options are needed to control Johne's disease in dairy herds. Recently, various strains of lactic acid bacteria (LAB), have been shown to inhibit the growth of M. paratuberculosis in fermented food (Van Brandt et al, 2011), providing the potential for its use to control infection in a suitable host. Current animal models for Johne's disease pathogenesis and vaccine studies are either inefficient (e.g., the intraperitoneal infection of mice) or expensive (e.g., the cow or goat models) (Hines et al, 2007).…”