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United States Department of Agriculture

Agricultural Research Service

Title: Heat Inactivation of Mycobacterium Paratuberculosis in Raw Milk: Are Current Pasteurization Conditions Effective?

item Stabel, Judith
item Steadham, Edward
item Bolin, Carole

Submitted to: International Virtual Conference on Infectious Diseases of Animals
Publication Type: Abstract Only
Publication Acceptance Date: April 20, 1997
Publication Date: N/A

Technical Abstract: Mycobacterium paratuberculosis, an acid-fast bacillus which causes enteritis in ruminants, has been suggested as an etiological agent of Crohn's disease in humans. The mode of transmission in unclear, however, some evidence suggests that humans may become infected via contaminated milk. Currently, it is not known whether commercial pasteurization effectively kills M. paratuberculosis in contaminated raw milk. Initially we designed experiments utilizing the holder-test tube method, simulating methodologies utilized in other laboratories, to determine optimal time/temperature combinations for effective inactivation of large numbers of M. paratuberculosis (10*8 CFU/ml). Results from these experiments indicate a significant reduction in viable bacterial numbers was achieved at 72C, but mean time for optimal time for optimal killing exceeded industry recommendations of 15 seconds at that temperature. Indeed, a residual population of viable M. paratuberculosis was detectable after 30 min incubation at 65, 72, 74, or 76C. In subsequent experiments, a laboratory-scale pasteurizer unit designed to simulate the high-temperature rt-time method (72C, 15 sec) currently used by commercial dairies was evaluated. Results from these experiments demonstrate that treatment of raw milk inoculated with live M. paratuberculosis (10*4, 10*6 CFU/ml) at 72C for 15 seconds effectively killed all the bacteria.

Last Modified: 4/22/2015
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