Effect of Commercial-Scale High-Temperature, Short-Time Pasteurization on the Viability ofMycobacterium paratuberculosisin Naturally Infected Cows' Milk

Abstract

Raw cows' milk naturally infected with Mycobacterium paratuberculosis was pasteurized with an APV HXP commercial-scale pasteurizer (capacity 2,000 liters/h) on 12 separate occasions. On each processing occasion, milk was subjected to four different pasteurization treatments, viz., 73°C for 15 s or 25 s with and without prior homogenization (2,500 lb/in 2 in two stages), in an APV Manton Gaulin KF6 homogenizer. Raw and pasteurized milk samples were tested for M. paratuberculosis by immunomagnetic separation (IMS)-PCR (to detect the presence of bacteria) and culture after decontamination with 0.75% (wt/vol) cetylpyridinium chloride for 5 h (to confirm bacterial viability). On 10 of the 12 processing occasions, M. paratuberculosis was detectable by IMS-PCR, culture, or both in either raw or pasteurized milk. Overall, viable M. paratuberculosis was cultured from 4 (6.7%) of 60 raw and 10 (6.9%) of 144 pasteurized milk samples. On one processing day, in particular, M. paratuberculosis appeared to have been present in greater abundance in the source raw milk (evidenced by more culture positives and stronger PCR signals), and on this occasion, surviving M. paratuberculosis bacteria were isolated from milk processed by all four heat treatments, i.e., 73°C for 15 and 25 s with and without prior homogenization. On one other occasion, surviving M. paratuberculosis bacteria were isolated from an unhomogenized milk sample that had been heat treated at 73°C for 25 s. Results suggested that homogenization increases the lethality of subsequent heat treatment to some extent with respect to M. paratuberculosis, but the extended 25-s holding time at 73°C was found to be no more effective at killing M. paratuberculosis than the standard 15-s holding time. This study provides clear evidence that M. paratuberculosis bacteria in naturally infected milk are capable of surviving commercial high-temperature, short-time pasteurization if they are present in raw milk in sufficient numbers.

Detection methods for Mycobacterium avium subsp paratuberculosis in milk and milk products: a review

“…MAP has also been detected after HTST, if more than 10 5 CFU/ml/milk were present in milk (Gao et al, 2002;Grant et al, 2002b). With regard to the fact that MAP cells may clump together in milk, pasteurization combined with homogenization is much more efficient than pasteurisation alone as documented by Grant et al (2005).…”

Risk Factors for the Presence of Mycobacterium avium spp. paratuberculosis in Human Intestinal Biopsies in Brazil

“…It is important to emphasize that, among the cases, 62.5% of subjects consumed raw milk, whereas only 10.8% of controls did so, as described in Table 4. According to Nielsen, et al (2008) even for the calves themselves, the intake of colostrum or milk, depending on the management of colostrum, may represent a risk factor for MAP infection [29,30].…”

Thermal Resistance of Mycobacterium Avium Subsp. Paratuberculosis

“…≥ 72 ºC przez ≥ 6 s, uzyskiwano zmniejszenie liczby Map do poziomu < 1 jtk/40 ml, przy początkowej ich liczbie ≤ 5 log jtk/ml [22,25,26]. W innych badaniach, w podobnych warunkach doświad-czalnych, w niektórych próbkach mleka pasteryzowanego wykrywano żywe komórki Map [11,16,23]. Z kolei Hammer i wsp.…”

“…Doświadczenia z zastosowaniem pasteryzatora przemysłowego pracującego w burzliwym przepływie cieczy, ale z mlekiem naturalnie zanieczyszczonym komór-kami Map, przeprowadzili Grant i wsp. [16]. Część próbek mleka poddanych pasteryzacji w temp.…”

“…XX w. ukazało się także wiele prac potwierdzających obecność Map w produktach mlecznych. Obecność żywych komórek tych drobnoustrojów stwierdzono w próbkach rynkowego mleka pasteryzowanego w Czechach, Wielkiej Brytanii, Stanach Zjednoczonych i Indiach [2,6,16,28], a także w próbkach serów w Czechach i Grecji [19].…”