Effective Heat Inactivation of Mycobacterium avium subsp. paratuberculosis in Raw Milk Contaminated with Naturally Infected Feces

Abstract

The effectiveness of high-temperature, short holding time (HTST) pasteurization and homogenization with respect to inactivation of Mycobacterium avium subsp. paratuberculosis was evaluated quantitatively. This allowed a detailed determination of inactivation kinetics. High concentrations of feces from cows with clinical symptoms of Johne's disease were used to contaminate raw milk in order to realistically mimic possible incidents most closely. Final M. avium subsp. paratuberculosis concentrations varying from 10 2 to 3.5 ؋ 10 5 cells per ml raw milk were used. Heat treatments including industrial HTST were simulated on a pilot scale with 22 different time-temperature combinations, including 60 to 90°C at holding (mean residence) times of 6 to 15 s. Following 72°C and a holding time of 6 s, 70°C for 10 and 15 s, or under more stringent conditions, no viable M. avium subsp. paratuberculosis cells were recovered, resulting in >4.2-to >7.1-fold reductions, depending on the original inoculum concentrations. Inactivation kinetic modeling of 69 quantitative data points yielded an E a of 305,635 J/mol and an lnk 0 of 107.2, corresponding to a D value of 1.2 s at 72°C and a Z value of 7.7°C. Homogenization did not significantly affect the inactivation. The conclusion can be drawn that HTST pasteurization conditions equal to 15 s at >72°C result in a more-than-sevenfold reduction of M. avium subsp. paratuberculosis.

Modeling the Effect of Direct and Indirect Contamination of On-Farm Bulk Tank Milk with Mycobacterium avium subsp. paratuberculosis

“…If pasteurization could be expected to reduce MAP in milk by 4 to 5 logs, the median concentrations found in our simulations are sufficiently low to ensure that all MAP in milk is reduced to very low levels. Previous studies on the effectiveness of heat inactivation of MAP suggest that up to a 7 log reduction of MAP can be obtained after heat inactivation (Rademaker et al, 2007). Our estimated MAP concentration in raw milk was 10 4 CFU/mL in the worst case; therefore heat inactivation should be effective.…”

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

“…Publications dealing with the culture detection of MAP in milk and milk products have also been increasing in number over the last decade (Rademaker et al, 2007;Stephan et al, 2007). From Table 1 it can be seen that MAP has been detected by culture in milk in countries with advanced dairy breeding systems on all continents; the positivity has ranged between 0.3 and 35.0%.…”

Thermal Resistance of Mycobacterium Avium Subsp. Paratuberculosis

“…W nielicznych badaniach [np. 16] zastosowano mleko surowe naturalnie zainfekowane Map lub jako inokulum użyto kału krów z kliniczną postacią choroby Johnego [26]. W najwcześniejszych badaniach nad ciepłoopornością Map prowadzono ogrzewanie sztucznie zanieczyszczonego mleka w probówkach lub szklanych kapilarach [4,13,30].…”

“…Gdy mleko pasteryzowano w urządzeniach przemysłowych, w temp. ≥ 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].…”

“…65 ÷ 70 ºC stosowana czasami podczas produkcji serów (tzw. subpasteryzacja lub termizacja) nie jest wystarczająca do całko-witego zniszczenia Map [8,23,25,26,29].…”