Detection of mycobacterium avium subsp. paratuberculosis in cheeses from small ruminants in Tuscany

• Map positivity was assessed by qPCR and culture in sheep and goat artisanal cheeses produced traditionally in Tuscany, Italy.
• Positive result were recorded by qPCR in 4/7 goat (57.14%), and 14/25 sheep (56%) cheeses. Positivity of farms by qPCR reached 66.6% (6/9).
• The only culture-positive result was recorded in connection to a qPCR-positive goat cheese sample. The isolate was identified as a Type S strain.
• Results indicate that cheeses may constitute a source of exposure to Map, although the questions remain about the viability of Map cells detected.

Paratuberculosis is an infectious disease which affects mainly domestic and wild ruminants caused by Mycobacterium avium subsp. paratuberculosis (Map). Map has been associated with human diseases like Crohn disease, type-1 diabetes, sarcoidosis, multiple sclerosis and Hashimoto's thyroiditis. The aim of this study was to determine the level of Map positivity of cheeses produced in Tuscany (Italy) as an indication of human exposure to the specific pathogen. Sampling was focused on artisanal cheeses produced without commercial starter culture from raw sheep or goat milk, on small-scale farms.Samples were tested by quantitative PCR (qPCR) and culture. Map DNA was detected in 4/7 (57.14%) goat, and in 14/25 (56%) sheep cheeses by qPCR, whereas cultivation produced a positive result in only one case. This corresponded to a goat cheese that had also reacted positively by qPCR and yielded a viable Type S (sheep) strain of Map. The Map load of the tested samples based on qPCR ranged from 6 × 10 to 1.8 × 104 Map cells/g of cheese. The results indicate on average 56.57% and 66.6% positivity of cheese samples and farms, respectively. Hence, the type of cheeses that were analyzed within the context of this study seem to constitute a considerable source of human exposure to Map; although the question remains of whether the Map cells were present in a viable form, since positive results were almost exclusively recorded by qPCR.