Proceedings of the 10th International Colloquium on Paratuberculosis

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#34 Viability <strong>of</strong> Mycobacterium avium subsp. paratuberculosis during traditional elaboration
and storage <strong>of</strong> yogurt
Karina Cirone, Yosef Daniel Huberman, Fernando Paolicchi,INTA EEA Balcarce, Argentina
Objective: In order to evaluate <strong>the</strong> viability <strong>of</strong> Map during traditional elaboration and storage <strong>of</strong> yogurt, an
inoculation experiment was conducted.
Materials and Methods: Typified strain <strong>of</strong> Map, previously isolated form commercial milk, was cultivated
onto HEYM. The bacterial suspension was adjusted to McFarland tube 0.5 using PBS (pH 7). A traditional
yogurt was prepared using 360mL <strong>of</strong> UAT milk with 125gr <strong>of</strong> commercial yogurt. Five mL <strong>of</strong> <strong>the</strong> bacterial
suspension was added. The mixture was incubated at 43ºC during 3 hours in shaker (New Brunswick Scientific
Exella 24). Once fermentation was complete it was kept at 4ºC for 20 days. Samples were taken out before
(T0) and throughout <strong>the</strong> elaboration process, every 45 minutes (T1, T2, T3 and T4), and afterwards, during
storage (T5: 4.5 Hs. T6: 24 Hs, T7: 48 Hs, T8: 4 days, T9: 10 days, T10: 15 days, and T11: 20 days). To each
sample pH and Map counts, after decontamination with 5% Oxalic Acid (Tacquet et al, 1980), were recorded.
Results: pH measurement: During <strong>the</strong> elaboration pH dropped from 6.1 at T0 to 4.7 at T7, while during
storage pH was kept stable at 4.4 (T8 – T12). Map viable count: Map viable counts were 127 CFU/mL at
T0. Map was not re-isolated from samples taken at T1 – T4. Map was detected at T5 (2.5 CFU/mL), gradually
increased up to 62.7 CFU/mL (T8) followed by a decrease to 0.33 CFU/mL (T11).
Discussion and Conclusion: Map may resist low pH levels and high temperatures during <strong>the</strong> traditional
elaboration <strong>of</strong> yogurt and its storage. During this process no viable Map were detected. Never<strong>the</strong>less, Map was
detected during storage showing adaptation to <strong>the</strong> new conditions <strong>of</strong> pH and temperature. Map counts are low
due to <strong>the</strong> decontamination process.
Map may be present in raw material, in low concentrations, and might survive elaboration process and
reach <strong>the</strong> final product.
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